Name: the synthesis, characterization and reactivity of a series of ruthenium n-triphosph complexes
Uploaded: 2015-04-10T14:00:00
Description: Watch this Scientific Journal Video about The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes at JoVE.com

AP is grateful to Imperial College London for a PhD studentship via the Frankland Chair endowment. Johnson Matthey plc are also thanked for the loan of the precious metal salts used in this work.

Note: Carry out all syntheses in a fume hood, and only after appropriate safety issues have been identified and measures taken to protect against them. Personal protective equipment include a lab coat, gloves and safety goggles and should be worn at all times.
1. Synthesis of N,N,N-tris(diphenylphosphinomethylene)amine, N(CH2PPh2)3 (N-triphosPh) (1)
<ol>
	<li>To a 200 ml oven dried Schlenk flask add diphenyl(hydroxymethylene)phosphonium chloride1...

<ol>
	<li>Bruneau, C., Dixneuf, P. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Ruthenium Catalysis and Fine Chemicals. , (2004).</li><li>Naota, T., Takaya, H., Murahashi, S. -. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ruthenium-Catalyzed+Reactions+for+Organic+Synthesis.">Ruthenium-Catalyzed Reactions for Organic Synthesis.</a> Chem. Rev. 98 (7), 2599-2660 (1998).</li><li>Arockaim, P. B., Bruneau, C., Dixneuf, P. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ruthenium(II)-Catalyzed+C-H+Bond+Activation+and+Functionalization.">Ruthenium(II)-Catalyzed C-H Bond Activation and Functionalization.</a> Chem. Rev. 112 (11), 5879-5918 (2012).</li><li>Trost, B. M., Toste, F. D., Pinkerton, A. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-metathesis+ruthenium-catalyzed+C-C+bond+formation.">Non-metathesis ruthenium-catalyzed C-C bond formation.</a> Chem. Rev. 101 (7), 2067-2096 (2001).</li><li>Vougioukalakis, G. C., Grubbs, R. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ruthenium-Based+Heterocyclic+Carbene-Coordinated+Olefin+Metathesis+Catalysis.">Ruthenium-Based Heterocyclic Carbene-Coordinated Olefin Metathesis Catalysis.</a> Chem. Rev. 110 (3), 1746-1787 (2010).</li><li>Lozano-Vila, A. M., Monsaert, S., Bajek, A., Verpoort, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ruthenium-based+olefin+metathesis+catalysts+derived+from+alkynes.">Ruthenium-based olefin metathesis catalysts derived from alkynes.</a> Chem. Rev. 110 (8), 4865-4909 (2010).</li><li>Samojlowicz, C., Bieniek, M., Grela, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ruthenium-based+olefin+metathesis+catalysts+bearing+N-heterocyclic+carbene+ligands.">Ruthenium-based olefin metathesis catalysts bearing N-heterocyclic carbene ligands.</a> Chem. Rev. 109 (8), 3708-3742 (2009).</li><li>Alcaide, B., Almedros, P., Luna, A. G. r. u. b. b. s. &. #. 8. 2. 1. 7. ;. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ruthenium-Carbenes+Beyond+the+Metathesis+Reaction:+Less+Conventional+Non-Metathetic+Utility.">Ruthenium-Carbenes Beyond the Metathesis Reaction: Less Conventional Non-Metathetic Utility.</a> Chem. Rev. 109 (8), 3817-3858 (2009).</li><li>Conley, B. L., Pennington-Boggio, M. K., Boz, E., Discovery Williams, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Applications,+and+Catalytic+Mechanisms+of+Shvo&#8217;s+Catalyst.">Applications, and Catalytic Mechanisms of Shvo&#8217;s Catalyst.</a> Chem. Rev. 110 (4), 2294-2312 (2010).</li><li>Miller, P. W., White, A. J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+preparation+of+multimetallic+complexes+using+sterically+bulky+N-centered+tipodal+dialkyl+phosphine+ligands.">The preparation of multimetallic complexes using sterically bulky N-centered tipodal dialkyl phosphine ligands.</a> J. Organomet. Chem. 695 (8), 1138-1145 (2010).</li><li>Hanton, M. J., Tin, S., Boardman, B. J., Miller, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ruthenium-catalysed+hydrogenation+of+esters+using+tripodal+phosphine+ligands.">Ruthenium-catalysed hydrogenation of esters using tripodal phosphine ligands.</a> J. Mol. Catal. A. 346 (1-2), 70-78 (2012).</li><li>Phanopoulos, A., Brown, N. J., White, A. J. P., Long, N. J., Miller, P. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis,+Characterization,+and+Reactivity+of+Ruthenium+Hydride+Complexes+of+N-Centered+Triphosphine+Ligands.">Synthesis, Characterization, and Reactivity of Ruthenium Hydride Complexes of N-Centered Triphosphine Ligands.</a> Inorg. Chem. 53 (7), 3742-3752 (2014).</li><li>Jin, G. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=N.N.N-tris(phosphinomethylen)amine+N.N.N&#8217;-tris(phosphinomethylene)hydrazine+N.N.N&#8217;.N&#8217;-tetra(phosphinomethylene)hydrazine.">N.N.N-tris(phosphinomethylen)amine N.N.N&#8217;-tris(phosphinomethylene)hydrazine N.N.N&#8217;.N&#8217;-tetra(phosphinomethylene)hydrazine.</a> Tetrahedron Lett. 22 (12), 1105-1108 (1981).</li><li>Walter, O., Huttner, G., Kern, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+and+Characterisation+of+N(CH2PPh2)3.+N(CH2PPh2)3Mo(CO)3+and+[HN(CH2PPh2)3Mo(CO)3]BF4.">Preparation and Characterisation of N(CH2PPh2)3. N(CH2PPh2)3Mo(CO)3 and [HN(CH2PPh2)3Mo(CO)3]BF4.</a> Z. Naturforsch. 51b, 922-928 (1996).</li><li>Fillol, J. L., Kruckenberg, A., Scherl, P., Wadepohl, H., Gade, L. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stitching+Phospholanes+Together+Piece+by+Piece:+New+Modular+Di-+and+Tridentate+Stereodirecting+Ligands.">Stitching Phospholanes Together Piece by Piece: New Modular Di- and Tridentate Stereodirecting Ligands.</a> Chem. Eur. J. 17 (50), 14047-14062 (2011).</li><li>Rodr&#237;guez, L. -. I., Roth, T., Fillol, J. L., Wadepohl, H., Gade, L. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+More+Gold&#8211;The+More+Enantioselective:+Cyclohydroaminations+of+&#947;-Allenyl+Sulfonamides+with+Mono+Bis,+and+Trisphospholane+Gold(I)+Catalysts.">The More Gold&#8211;The More Enantioselective: Cyclohydroaminations of &#947;-Allenyl Sulfonamides with Mono Bis, and Trisphospholane Gold(I) Catalysts.</a> Chem. Eur. J. 18 (12), 3721-3728 (2012).</li><li>Scherl, P., Kruckenberg, A., Mader, S., Wadepohl, H., Gade, L. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ruthenium+&#951;4-Trimethylenemethane+Complexes+Containing+Tripodal+Phosphanomethylamine+Ligands.">Ruthenium &#951;4-Trimethylenemethane Complexes Containing Tripodal Phosphanomethylamine Ligands.</a> Organometallics. 31 (19), 7024-7027 (2012).</li><li>Scherl, P., Wadepohl, H., Gade, L. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogenation+and+Silylation+of+a+Double-Cyclometalated+Ruthenium+Complex:+Structures+and+Dynamic+Behavior+of+Hydrido+and+Hydridosilicate+Ruthenium+Complexes.">Hydrogenation and Silylation of a Double-Cyclometalated Ruthenium Complex: Structures and Dynamic Behavior of Hydrido and Hydridosilicate Ruthenium Complexes.</a> Organometallics. 32 (15), 4409-4415 (2013).</li><li>Geilen, F. M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selective+and+Flexible+Transformation+of+Biomass-Derived+Platform+Chemicals+by+a+Multifunctional+Catalytic+System.">Selective and Flexible Transformation of Biomass-Derived Platform Chemicals by a Multifunctional Catalytic System.</a> Angew. Chem. Int. Ed. 49 (32), 5510-5514 (2010).</li><li>Geilen, F. M. A., Engendahl, B., H&#246;lscher, M., Klankermayer, J., Leitner, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selective+Homogeneous+Hydrogenation+of+Biogenic+Carboxylic+Acids+with+[Ru(TriPhos)H]+:+A+Mechanistic+Study.">Selective Homogeneous Hydrogenation of Biogenic Carboxylic Acids with [Ru(TriPhos)H]+: A Mechanistic Study.</a> J. Am. Chem. Soc. 133 (36), 14349-14358 (2011).</li><li>Van Engelen, M. C., Teunissen, H. T., de Vries, J. G., Elsevier, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Suitable+ligands+for+homogeneous+ruthenium-catalyzed+hydrogenolysis+of+esters.">Suitable ligands for homogeneous ruthenium-catalyzed hydrogenolysis of esters.</a> J. Mol. Catal. A. 206 (1-2), 185-192 (2003).</li><li>Wesselbaum, S., vom Stein, T., Klankermayer, J., Leitner, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogenation+of+Carbon+Dioxide+to+Methanol+by+Using+a+Homogeneous+Ruthenium&#8211;Phosphine+Catalyst.">Hydrogenation of Carbon Dioxide to Methanol by Using a Homogeneous Ruthenium&#8211;Phosphine Catalyst.</a> Angew. Chem. Int. Ed. 51 (30), 7499-7502 (2012).</li><li>Fillol, J. L., Kruckenberg, A., Scherl, P., Wadepohl, H., Gade, L. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stitching+Phospholanes+Together+Piece+by+Piece:+New+Modular+Di-+and+Tridentate+Stereodirecting+Ligands.">Stitching Phospholanes Together Piece by Piece: New Modular Di- and Tridentate Stereodirecting Ligands.</a> Chem. Eur. J. 17 (50), 14047-14062 (2011).</li><li>Rodr&#237;guez, L. -. I., Roth, T., Fillol, J. L., Wadepohl, H., Gade, L. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+More+Gold&#8211;The+More+Enantioselective:+Cyclohydroaminations+of+&#947;-Allenyl+Sulfonamides+with+Mono+Bis-,+and+Trisphospholane+Gold(I)+Catalysts.">The More Gold&#8211;The More Enantioselective: Cyclohydroaminations of &#947;-Allenyl Sulfonamides with Mono Bis-, and Trisphospholane Gold(I) Catalysts.</a> Chem. Eur. J. 18 (12), 3721-3728 (2012).</li><li>Scherl, P., Wadepohl, H., Gade, L. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogenation+and+Silylation+of+a+Double-Cyclometalated+Ruthenium+Complex:+Structures+and+Dynamic+Behavior+of+Hydrido+and+Hydridosilicate+Ruthenium+Complexes.">Hydrogenation and Silylation of a Double-Cyclometalated Ruthenium Complex: Structures and Dynamic Behavior of Hydrido and Hydridosilicate Ruthenium Complexes.</a> Organometallics. 32 (15), 4409-4415 (2013).</li><li>Bennett, B. K., Richmond, T. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+Inexpensive,+Disposable+Cannula+Filtration+Device.">An Inexpensive, Disposable Cannula Filtration Device.</a> J. Chem. Educ. 75 (8), 1034 (1998).</li><li>Judd, C. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proton+NMR+Basics.">Proton NMR Basics.</a> J. Chem. Educ. 72 (8), 706 (1995).</li><li>Rhodes, L. F., Venanzi, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ruthenium(II)-Assisted+Borohydride+Reduction+of+Acetonitrile.">Ruthenium(II)-Assisted Borohydride Reduction of Acetonitrile.</a> Inorg. Chem. 26 (16), 2692-2695 (1987).</li><li>Bakhmutov, V. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In-depth+NMR+and+IR+study+of+the+proton+transfer+equilibrium+between+[{MeC(CH2PPh2)3}Ru(CO)H2]+and+hexafluoroisopropanol.">In-depth NMR and IR study of the proton transfer equilibrium between [{MeC(CH2PPh2)3}Ru(CO)H2] and hexafluoroisopropanol.</a> Can. J. Chem. 79, 479-489 (2001).</li></ol>

Herein we have described efficient synthetic procedures for the synthesis of a tridentate phosphine ligand and a series of ruthenium complexes. The N-triphosPh ligand (1) can be easily prepared in high yield with a minimalistic work-up procedure. This phosphorus based Mannich reaction used to synthesize these types of ligands is quite general and can be used for other ligand derivatives with differing R-groups on the P-atoms.10-12,15-18 Additionally, this synthetic methodol...

Ruthenium phosphine based complexes are some of the most widely studied and chemically versatile molecular catalysts.1-9 Typically, such ruthenium catalysts contain either mono- or bi-dentate ligands that dictate the electronics, sterics, geometry and solubility of the complex, and which profoundly impact on catalytic activity. Multidentate phosphine systems have been less widely studied for catalysis, as they are known to impart greater stability on the metal center owing to the greater chelate effect of multiple phosphorus donors on the metal center. Such stabilization can be undesirable for catalysis, however, under harsher reaction conditions (higher temperatures and pressures) the complex stabilizing properties of such ligands can be advantageous in ensuring catalyst integrity. One such multidentate phosphine ligand system that we10-12 and others13-18 have investigated for imparting complex stability and facial coordination geometries is the so-called N-triphos ligand series where three phosphine arms are attached to an apical bridging nitrogen atom forming a potentially tridentate ligand. One of the key features to these particular ligands is the facile way that they can be synthesized via a phosphorus based Mannich reaction from readily available secondary phosphines (Figure 1), hence phosphines with a variety of R-groups can be prepared usually in high yields and with minimal work-up. The overall goal of this methodology is to present a facile route by which ruthenium dihydride complexes featuring N-triphos ligands can be accessed for subsequent catalytic applications. Recently, Ru-triphos based complexes have attracted attention as catalysts for the hydrogenation reactions of biomass derived products, such as levulinic acid,19,20 bio-esters11,21 and carbon dioxide22 to higher value chemicals. It would be advantageous to expand the scope of Ru-triphos derivatives that are either as, or more active than the systems already reported, especially if they are synthetically easier to access, such as the N-triphos ligand. The most studied carbon-centered analogue typically suffers from low yielding synthesis and involves highly air-sensitive metal phosphide reagents, unlike the N-triphos ligand, which is more adaptable and easier to prepare.10-18
N-triphos ligands remain relatively under-investigated, with only molybdenum, tungsten, ruthenium, rhodium and gold complexes having been reported from nine publications. This is in stark contrast to the boron- and carbon-centered analogues, for which there are around 50 and 900 articles, respectively, with a great number of unique compounds. Nonetheless, N-triphos containing complexes have found application in the asymmetric catalytic hydrogenation of pro-chiral olefins23 as well as asymmetric cyclohydroamination of N-protected &#947;-allenyl sulfonamides.24 Additionally, a ruthenium complex coordinated by a bulky N-triphos ligand featuring phospholane coordinating moieties was found to activate silanes, a key step in the development of organosilicon chemistry.25
As part of the ongoing research program in catalysis, we sought to prepare a range of ruthenium N-triphosPh precatalysts and to investigate their stoichiometric reactions and catalytic potential. Despite molybdenum complexes of N-triphosPh having first been reported over 25 years ago, their application, catalytic or otherwise has not been investigated. This work demonstrates the applicability of the N-triphos scaffold, which despite being generally underdeveloped, possess many desirable features such as complex stability. Herein we report the synthetic route and characterization of to a series of ruthenium N-triphosPh complexes that may find application in catalytic hydrogenation reactions.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Methanol</td>
			<td rowspan="5">&#8211;</td>
			<td rowspan="5">&#8211;</td>
			<td rowspan="5">Obtained from in-house solvent purification system: Innovative Technology, inc &#34;pure solv&#34; drying tower. Stored in ampules over activated molecular sieves under nitrogen.</td>
		</tr>
		<tr>
			<td>Toluene</td>
		</tr>
		<tr>
			<td>Diethyl Ether</td>
		</tr>
		<tr>
			<td>Tetrahydrofuran (THF)</td>
		</tr>
		<tr>
			<td>Acetonitrile</td>
		</tr>
		<tr>
			<td>d6-Acetone</td>
			<td>VWR</td>
			<td>VWRC87152.0011</td>
			<td>Store in fridge</td>
		</tr>
		<tr>
			<td>Triethylamine</td>
			<td>Sigma-Aldrich</td>
			<td>TO886-1L</td>
			<td>Distilled and stored over activated molecular sieves under N2</td>
		</tr>
		<tr>
			<td>2M Ammonia solution in methanol</td>
			<td>Sigma-Aldrich</td>
			<td>341428-100ML</td>
			<td>Solution comes in a &#34;Sure-Seal&#34; bottle</td>
		</tr>
		<tr>
			<td>NH4PF6</td>
			<td>Sigma-Aldrich</td>
			<td>216593-5G</td>
			<td>Store in desiccator</td>
		</tr>
		<tr>
			<td>Levulinic Acid</td>
			<td>Acros Organics</td>
			<td>125142500</td>
			<td>Solid but melts close to room temperature</td>
		</tr>
		<tr>
			<td>3 &#197; Molecular sieves</td>
			<td>Alfa Aesar</td>
			<td>LO5359</td>
			<td>Activate by heating over night under vacuum</td>
		</tr>
		<tr>
			<td>Schlenk flasks</td>
			<td>GPE</td>
			<td>Custom design</td>
			<td>&#8211;</td>
		</tr>
		<tr>
			<td>Dual-manifold Schlenk line</td>
			<td>GPE</td>
			<td>Custom design</td>
			<td>Dual-manifold of i) N2 that has been passed through a silica drying column and ii) vacuum.</td>
		</tr>
		<tr>
			<td>Rotary vacuum pump</td>
			<td>Edwards</td>
			<td>RV3 A652-01-903</td>
			<td>&#8211;</td>
		</tr>
		<tr>
			<td>100 ml Autoclave Engineer&#39;s high pressure reactor</td>
			<td>Autoclave Engineer</td>
			<td>Custon design</td>
			<td>&#8211;</td>
		</tr>
		<tr>
			<td>Vortex Stirrer</td>
			<td>VWR</td>
			<td>444-1378</td>
			<td>&#8211;</td>
		</tr>
	</tbody>
</table>

the synthesis, characterization and reactivity of a series of ruthenium n-triphosph complexes

Herein we report the synthesis of a tridentate phosphine ligand N(CH2PPh2)3 (N-triphosPh) (1) via a phosphorus based Mannich reaction of the hydroxylmethylene phosphine precursor with ammonia in methanol under a nitrogen atmosphere. The N-triphosPh ligand precipitates from the solution after approximately 1 hr of reflux and can be isolated analytically pure via simple cannula filtration procedure under nitrogen. Reaction of the N-triphosPh ligand with [Ru3(CO)12] under reflux affords a deep red solution that show evolution of CO gas on ligand complexation. Orange crystals of the complex [Ru(CO)2{N(CH2PPh2)3}-&#954;3P] (2) were isolated on cooling to RT. The 31P{1H} NMR spectrum showed a characteristic single peak at lower frequency compared to the free ligand. Reaction of a toluene solution of complex 2 with oxygen resulted in the instantaneous precipitation of the carbonate complex [Ru(CO3)(CO){N(CH2PPh2)3}-&#954;3P] (3) as an air stable orange solid. Subsequent hydrogenation of 3 under 15 bar of hydrogen in a high-pressure reactor gave the dihydride complex [RuH2(CO){N(CH2PPh2)3}-&#954;3P] (4), which was fully characterized by X-ray crystallography and NMR spectroscopy. Complexes 3 and 4 are potentially useful catalyst precursors for a range of hydrogenation reactions, including biomass-derived products such as levulinic acid (LA). Complex 4 was found to cleanly react with LA in the presence of the proton source additive NH4PF6 to give [Ru(CO){N(CH2PPh2)3}-&#954;3P{CH3CO(CH2)2CO2H}-&#954;2O](PF6) (6).

The N-triphosPh ligand (1) and the ruthenium complex series: Ru(CO)2{N(CH2PPh2)3}-&#954;3P] (2), [Ru(CO3)(CO){N(CH2PPh2)3}-&#954;3P] (3) and [Ru(H)2(CO){N(CH2PPh2)3}-&#954;3P] (4) were characterized via 1H, 13C{1H...

Watch this Scientific Journal Video about The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes at JoVE.com

The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes

Ruthenium phosphine complexes are widely used for homogeneous catalytic reactions such as hydrogenations. The synthesis of a series of novel tridentate ruthenium complexes bearing the N-triphos ligand N(CH2PPh2)3 is reported. Additionally, the stoichiometric reaction of a dihydride Ru&#8211;N-triphos complex with levulinic acid is described.

The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes

Herein we report the synthesis of a tridentate phosphine ligand N(CH2PPh2)3 (N-triphosPh) (1) via a phosphorus based Mannich reaction of the ...

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Chemistry

Production of Disulfide-stabilized Transmembrane Peptide Complexes for Structural Studies

Physical interactions among the lipid-embedded alpha-helical domains of membrane proteins play a crucial role in folding and assembly of membrane protein complexes and in dynamic processes such as transmembrane (TM) signaling and regulation of cell-surface protein levels. Understanding the structural features driving the association of particular sequences requires sophisticated biophysical and biochemical analyses of TM peptide complexes. However, the extreme hydrophobicity of TM domains makes them very difficult to manipulate using standard peptide chemistry techniques, and production of suitable study material often proves prohibitively challenging. Identifying conditions under which peptides can adopt stable helical conformations and form complexes spontaneously adds a further level of difficulty. Here we present a procedure for the production of homo- or hetero-dimeric TM peptide complexes from materials that are expressed in E. coli, thus allowing incorporation of stable isotope labels for nuclear magnetic resonance (NMR) or non-natural amino acids for other applications relatively inexpensively. The key innovation in this method is that TM complexes are produced and purified as covalently associated (disulfide-crosslinked) assemblies that can form stable, stoichiometric and homogeneous structures when reconstituted into detergent, lipid or other membrane-mimetic materials. We also present carefully optimized procedures for expression and purification that are equally applicable whether producing single TM domains or crosslinked complexes and provide advice for adapting these methods to new TM sequences.

Biophysical and biochemical studies of interactions among membrane-embedded protein domains face many technical challenges, the first of which is obtaining appropriate study material. This article describes a protocol for producing and purifying disulfide-stabilized transmembrane peptide complexes that are suitable for structural analysis by solution nuclear magnetic resonance (NMR) and other analytical applications.

Physical  interactions among the lipid-embedded alpha-helical domains of membrane  proteins play a crucial role in folding and assembly of membrane ...

Isolation and Chemical Characterization of Lipid A from Gram-negative Bacteria

Lipopolysaccharide (LPS) is the major cell surface molecule of gram-negative bacteria, deposited on the outer leaflet of the outer membrane bilayer. LPS can be subdivided into three domains: the distal O-polysaccharide, a core oligosaccharide, and the lipid A domain consisting of a lipid A molecular species and 3-deoxy-D-manno-oct-2-ulosonic acid residues (Kdo). The lipid A domain is the only component essential for bacterial cell survival. Following its synthesis, lipid A is chemically modified in response to environmental stresses such as pH or temperature, to promote resistance to antibiotic compounds, and to evade recognition by mediators of the host innate immune response. The following protocol details the small- and large-scale isolation of lipid A from gram-negative bacteria. Isolated material is then chemically characterized by thin layer chromatography (TLC) or mass-spectrometry (MS). In addition to matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) MS, we also describe tandem MS protocols for analyzing lipid A molecular species using electrospray ionization (ESI) coupled to collision induced dissociation (CID) and newly employed ultraviolet photodissociation (UVPD) methods. Our MS protocols allow for unequivocal determination of chemical structure, paramount to characterization of lipid A molecules that contain unique or novel chemical modifications. We also describe the radioisotopic labeling, and subsequent isolation, of lipid A from bacterial cells for analysis by TLC. Relative to MS-based protocols, TLC provides a more economical and rapid characterization method, but cannot be used to unambiguously assign lipid A chemical structures without the use of standards of known chemical structure. Over the last two decades isolation and characterization of lipid A has led to numerous exciting discoveries that have improved our understanding of the physiology of gram-negative bacteria, mechanisms of antibiotic resistance, the human innate immune response, and have provided many new targets in the development of antibacterial compounds.

Isolation and characterization of the lipid A domain of lipopolysaccharide (LPS) from gram-negative bacteria provides insight into cell surface based mechanisms of antibiotic resistance, bacterial survival and fitness, and how chemically diverse lipid A molecular species differentially modulate host innate immune responses.

Lipopolysaccharide (LPS) is the major cell surface molecule of gram-negative bacteria, deposited on the outer leaflet of the outer membrane bilayer. LPS ...

Anticancer Metal Complexes: Synthesis and Cytotoxicity Evaluation by the MTT Assay

Titanium (IV) and vanadium (V) complexes are highly potent anticancer agents. A challenge in their synthesis refers to their hydrolytic instability; therefore their preparation should be conducted under an inert atmosphere. Evaluation of the anticancer activity of these complexes can be achieved by the MTT assay.
The MTT assay is a colorimetric viability assay based on enzymatic reduction of the MTT molecule to formazan when it is exposed to viable cells. The outcome of the reduction is a color change of the MTT molecule. Absorbance measurements relative to a control determine the percentage of remaining viable cancer cells following their treatment with varying concentrations of a tested compound, which is translated to the compound anticancer activity and its IC50 values. The MTT assay is widely common in cytotoxicity studies due to its accuracy, rapidity, and relative simplicity.
Herein we present a detailed protocol for the synthesis of air sensitive metal based drugs and cell viability measurements, including preparation of the cell plates, incubation of the compounds with the cells, viability measurements using the MTT assay, and determination of IC50 values.

A method for synthesis of air-sensitive titanium and vanadium anticancer agents is described, along with the evaluation of their cytotoxic activity towards human cancer cell line by the MTT Assay.

Titanium (IV) and vanadium (V) complexes are highly potent anticancer agents. A challenge in their synthesis refers to their hydrolytic instability; ...

Split-and-pool Synthesis and Characterization of Peptide Tertiary Amide Library

Peptidomimetics are great sources of protein ligands. The oligomeric nature of these compounds enables us to access large synthetic libraries on solid phase by using combinatorial chemistry. One of the most well studied classes of peptidomimetics is peptoids. Peptoids are easy to synthesize and have been shown to be proteolysis-resistant and cell-permeable. Over the past decade, many useful protein ligands have been identified through screening of peptoid libraries. However, most of the ligands identified from peptoid libraries do not display high affinity, with rare exceptions. This may be due, in part, to the lack of chiral centers and conformational constraints in peptoid molecules. Recently, we described a new synthetic route to access peptide tertiary amides (PTAs). PTAs are a superfamily of peptidomimetics that include but are not limited to peptides, peptoids and N-methylated peptides. With side chains on both &#945;-carbon and main chain nitrogen atoms, the conformation of these molecules are greatly constrained by sterical hindrance and allylic 1,3 strain. (Figure 1) Our study suggests that these PTA molecules are highly structured in solution and can be used to identify protein ligands. We believe that these molecules can be a future source of high-affinity protein ligands. Here we describe the synthetic method combining the power of both split-and-pool and sub-monomer strategies to synthesize a sample one-bead one-compound (OBOC) library of PTAs.

Peptide tertiary amides (PTAs) are a superfamily of peptidomimetics that include but are not limited to peptides, peptoids and N-methylated peptides. Here we describe a synthetic method which combines&#160;both split-and-pool and sub-monomer strategies to synthesize a one-bead one-compound library of PTAs.

Peptidomimetics are great sources of protein ligands. The oligomeric nature of these compounds enables us to access large synthetic libraries on solid ...

Nucleoside Triphosphates - From Synthesis to Biochemical Characterization

The traditional strategy for the introduction of chemical functionalities is the use of solid-phase synthesis by appending suitably modified phosphoramidite precursors to the nascent chain. However, the conditions used during the synthesis and the restriction to rather short sequences hamper the applicability of this methodology. On the other hand, modified nucleoside triphosphates are activated building blocks that have been employed for the mild introduction of numerous functional groups into nucleic acids, a strategy that paves the way for the use of modified nucleic acids in a wide-ranging palette of practical applications such as functional tagging and generation of ribozymes and DNAzymes. One of the major challenges resides in the intricacy of the methodology leading to the isolation and characterization of these nucleoside analogues.
	
	In this video article, we present a detailed protocol for the synthesis of these modified analogues using phosphorous(III)-based reagents. In addition, the procedure for their biochemical characterization is divulged, with a special emphasis on primer extension reactions and TdT tailing polymerization. This detailed protocol will be of use for the crafting of modified dNTPs and their further use in chemical biology.

The protocol described herein aims to explain and abridge the numerous obstacles in the way of the intricate route leading to modified nucleoside triphosphates. Consequently, this protocol facilitates both the synthesis of these activated building-blocks and their availability for practical applications.

The  traditional strategy for the introduction of chemical functionalities is the  use of solid-phase synthesis by appending suitably modified ...

Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

Synthesis and Characterization of Supramolecular Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical properties for applications in photonics, drug delivery and coating technology. Here we present a new family of colloidal building blocks, coined supramolecular colloids, whose self-assembly is controlled through surface-functionalization with a benzene-1,3,5-tricarboxamide (BTA) derived supramolecular moiety. Such BTAs interact via directional, strong, yet reversible hydrogen-bonds with other identical BTAs. Herein, a protocol is presented that describes how to couple these BTAs to colloids and how to quantify the number of coupling sites, which determines the multivalency of the supramolecular colloids. Light scattering measurements show that the refractive index of the colloids is almost matched with that of the solvent, which strongly reduces the van der Waals forces between the colloids. Before photo-activation, the colloids remain well dispersed, as the BTAs are equipped with a photo-labile group that blocks the formation of hydrogen-bonds. Controlled deprotection with UV-light activates the short-range hydrogen-bonds between the BTAs, which triggers the colloidal self-assembly. The evolution from the dispersed state to the clustered state is monitored by confocal microscopy. These results are further quantified by image analysis with simple routines using ImageJ and Matlab. This merger of supramolecular chemistry and colloidal science offers a direct route towards light- and thermo-responsive colloidal assembly encoded in the surface-grafted monolayer.

A protocol for the synthesis and characterization of colloids coated with supramolecular moieties is described. These supramolecular colloids undergo self-assembly upon the activation of the hydrogen-bonds between the surface-anchored molecules by UV-light.

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical ...

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level

We demonstrate a method for the synthesis of cyclic polymers and a protocol for characterizing their diffusive motion in a melt state at the single molecule level. An electrostatic self-assembly and covalent fixation (ESA-CF) process is used for the synthesis of the cyclic poly(tetrahydrofuran) (poly(THF)). The diffusive motion of individual cyclic polymer chains in a melt state is visualized using single molecule fluorescence imaging by incorporating a fluorophore unit in the cyclic chains. The diffusive motion of the chains is quantitatively characterized by means of a combination of mean-squared displacement (MSD) analysis and a cumulative distribution function (CDF) analysis. The cyclic polymer exhibits multiple-mode diffusion which is distinct from its linear counterpart. The results demonstrate that the diffusional heterogeneity of polymers that is often hidden behind ensemble averaging can be revealed by the efficient synthesis of the cyclic polymers using the ESA-CF process and the quantitative analysis of the diffusive motion at the single molecule level using the MSD and CDF analyses.

A protocol for the synthesis and characterization of diffusive motion of cyclic polymers at the single molecule level is presented.

We demonstrate a method for the synthesis of cyclic polymers and a protocol for characterizing their diffusive motion in a melt state at the single ...

Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of Chalcogenidoplumbates(II or IV)

The phases of &#34;PbCh2&#34; (Ch = Se, Te) are obtained from solid-state syntheses (i.e., by the fusion of the elements under inert conditions in silica glass ampules). Reduction of such phases by elemental alkaline metals in amines affords crystalline chalcogenidoplumbate(II) salts comprised of [PbTe3]2- or [Pb2Ch3]2- anions, depending upon which sequestering agent for the cations is present: crown ethers, like 18-crown-6, or cryptands, like [2.2.2]crypt. Reactions of solutions of such anions with transition-metal compounds yield (poly-)chalcogenide anions or transition-metal chalcogenide clusters, including one with a &#181;-PbSe ligand (i.e., the heaviest-known CO homolog).
In contrast, the solid-state synthesis of a phase of the nominal composition &#34;K2PbSe2&#34; by successive reactions of the elements and by the subsequent solvothermal treatment in amines yields the first non-oxide/halide inorganic lead(IV) compound: a salt of the ortho-selenidoplumbate(IV) anion [PbSe4]4-. This was unexpected due to the redox potentials of Pb(IV) and Se(-II). Such methods can further be applied to other elemental combinations, leading to the formation of solutions with binary [HgTe2]2- or [BiSe3]3- anions, or to large-scale syntheses of K2Hg2Se3 or K3BiSe3 via the solid-state route.
All compounds are characterized by single-crystal X-ray diffraction and elemental analysis; solutions of plumbate salts can be investigated by 205Pb and 77Se or 127Te NMR techniques. Quantum chemical calculations using density functional theory methods enable energy comparisons. They further allow for insights into the electronic configuration and thus, the bonding situation. Molecular Rh-containing Chevrel-type compounds were found to exhibit delocalized mixed valence, whereas similar telluridopalladate anions are electron-precise; the cluster with the &#181;-PbSe ligand is energetically favored over a hypothetical CO analog, in line with the unsuccessful attempt at its synthesis. The stability of formal Pb(IV) within the [PbSe4]4- anion is mainly due to a suitable stabilization within the crystal lattice.

Combining Solid-state and Solution-based Techniques: Synthesis and Reactivity of ChalcogenidoplumbatesII or IV

The synthesis of chalcogenidoplumbates(II,IV) via the in situ reduction of nominal "PbCh2" (Ch = Chalcogen) and via a solid-state reaction and subsequent solvothermal reactions is presented. Additionally, reactivities of plumbate(II) solutions are portrayed, which yield the heaviest-known CO homolog known to date: the &#181;-PbSe ligand.

The phases of &#34;PbCh2&#34; (Ch = Se, Te) are obtained from solid-state syntheses (i.e., by the fusion of the elements under inert conditions in silica ...

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. Detailed and generalized protocols are also presented for testing the catalytic activity of such complexes in arylation and Suzuki-Miyaura cross-coupling reactions. Representative results are shown for the catalytic activity of the four complexes in arylation and Suzuki-Miyaura type reactions. For each of the reactions investigated, at least one of the four complexes successfully catalyzed the reaction, qualifying them as promising candidates for catalysis of many carbon-carbon bond-forming reactions. The protocols presented are general enough to be adapted for the synthesis, purification and catalytic activity testing of new palladium N-heterocyclic carbene complexes.

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. The complexes were tested for catalytic activity in arylation and Suzuki-Miyaura reactions. For each reaction investigated, at least one of the four complexes successfully catalyzed the reaction.

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from ...