Phosphine Coordination Research Articles

Influence of arene dissociation and phosphine coordination on the catalytic activity of [RuCl( κ2-triphos)( p-cymene)]PF 6

The catalytic activity of a ruthenium(II)- p-cymene complex containing a partially coordinated triphosphine ligand, [RuCl( κ 2-triphos)( p-cymene)]PF 6 1, has been investigated in the hydrogenation of styrene to ethylbenzene. The influence of arene dissociation and coordination of the free phosphine donor group on the catalytic activity have been probed directly and indirectly by comparison to structural analogues. Analogues of 1 containing in a diphosphine ligand, [RuCl( κ 2-dppp)( p-cymene)]PF 6 2, or a labile arene ligand, [RuCl( κ 2-triphos)( η 6-PhCO 2Et)]PF 6 3, show significantly enhanced catalytic activity – demonstrating the importance of ligand coordination/dissociation dynamics in ruthenium(II)-arene compounds during catalysis. These observations are supported by thermolysis reactions of 1 in DMSO. In addition, improved syntheses of 1 and 2 are reported together with the solid-state structures of syn- 1, syn- 3 and [Ru( η 3-C 8H 13)( κ 3-triphos)]PF 6.

A coordination polymer of (Ph3P)AuCl prepared by post-synthetic modification and its application in 1-hexene/n-hexane separation

PCM-10 is a porous phosphine coordination material based on Ca(II) and tris(p-carboxylated) triphenylphosphine. The material provides a unique 3-dimensional surface of P(III) Lewis base sites, which is ideal for post-synthetic functionalization. The addition of Au(I) yields an advanced material that can selectively adsorb 1-hexene over n-hexane at room temperature.

High capacity CO2 adsorption in a Mg(ii)-based phosphine oxide coordination material

The new porous phosphine coordination material, PCM-11, is an unusual 8,4-connected coordination polymer with an open 3-D pore structure, formed by reaction of Mg(II) with tris(para-carboxylato)triphenylphosphine oxide. The highly ionic nature of the metal-ligand bonding results in excellent thermal stability upon desolvation (>460 °C). PCM-11 is easily activated for small molecule sorption at low temperature without the requirement for solvent pre-exchange. It adsorbs 47.5 wt% CO(2) at 11.6 bar and 30 °C.

An Organocatalytic β-Boration of α,β-Unsaturated Carbonyl Compounds

The authors report a chiral phospine-1-catalyzed β-boration of α,β-unsaturated carbonyl compounds using (Bpin)2 as borylating agent. The products were obtained in high conversions and optical purities. The mechanistic rationale is based on the phosphine coordination to one of the boron atoms, inducing a high polarization and presumably partial dissociation of the B-B bond. Thus, the potentially more nucleophilic boron atom could as such add to the double bond of the substrate in a phosphine-mediated chiral environment. Alcoholysis of the intermediate can then liberate the product and the boronic acid ester byproduct.

Variable-Temperature NMR Studies of Soluble Polymer-Supported Phosphine−Silver Complexes

The use of polymers as supports for organometallic catalysts has received wide attention. However, catalyst reactivity is sometimes altered as a consequence of catalyst immobilization by a polymeric ligand and such altered reactivity can complicate such supported catalysts' use. The results in this study show that heptane phase selectively soluble polyisobutylene (PIB)-bound phosphine ligands have essentially identical kinetic behavior when compared to electronically similar isobutyldiphenylphosphine analogues in phosphine coordination and exchange in silver(I) halide complexes. These studies used variable-temperature (31)P NMR spectroscopy to probe the silver-phosphine exchange processes for both AgI and AgCl complexes of these polymeric and low molecular weight phosphine ligands. The results show that the dynamic behavior of the PIB- and isobutyldiphenylphosphine-AgX complexes is nearly identical based on line-shape analysis of these (31)P NMR spectra as a function of temperature. Similar studies of more polar poly(ethylene glycol)triarylphosphine-bound AgX complexes and electronically analogous low molecular weight AgX complexes have similar behavior in variable-temperature (31)P NMR spectroscopy.

Synthesis and characterization of carboxy-functionalized diiron model complexes of [FeFe]-hydrogenases: Decarboxylation of Ph2PCH2COOH promoted by a diiron azadithiolate complex

Abstract Two carboxy-functionalized diiron complexes [{(μ-SCH2)2X}{Fe(CO)3}{Fe(CO)2L}] (X = NC3H7, L = Ph2PCH2CH2COOH, 4; X = CH2, L = Ph2PCH2COOH, 5) were prepared, as biomimetic models of the [FeFe] hydrogenase active site, from the CO-replacement of [{(μ-SCH2)2NC3H7}Fe2(CO)6] (1) and (μ-pdt)Fe2(CO)6 (2) by phosphine ligands in CH3CN at 40 °C, respectively. In contrast, the reaction of 1 with Ph2PCH2COOH under the same condition afforded complex [{(μ-SCH2)2NC3H7}{Fe(CO)3}{Fe(CO)2(Ph2PCH3)}] (3) with a decarboxylated phosphine ligand. The molecular structures of complexes 3–5 were determined by X-ray crystallographic analyses, which show that they have similar frameworks with the phosphine ligand on the apical position. The interesting C–H···S contacts between the methylene hydrogen atoms of the PhCH2COOH ligand and the μ-S atoms of the pdt-bridge are found in the crystal of 5. According to the experimental evidence, a plausible mechanism, via sequential phosphine coordination, N-protonation, and decarboxylation steps, is proposed for the formation of 3 and for explanation of the contrastive reactivities of the adt- (2-aza-1,3-propanedithiolato) and the pdt- (1,3-propanedithiolato) bridged diiron complexes toward decarboxylation of the Ph2PCH2COOH ligand.

Metal–organophosphine and metal–organophosphonium frameworks with layered honeycomb-like structures

Phosphanotriylbenzenecarboxylic acid (ptbcH(3); P(C(6)H(4)-p-CO(2)H)(3)) and its methyl phosphonium iodide derivative (mptbcH(3)I; {H(3)CP(C(6)H(4)-p-CO(2)H)(3)}I) have been used as organic building blocks in reaction with Zn(ii) salts to obtain a series of related two-dimensional coordination polymers with honeycomb-like networks. The variable coordination number and oxidation states available to phosphorus have been exploited to produce a family of related phosphine coordination materials (PCMs) using a single ligand precursor. The phosphine carboxylate trianion, ptbc(3-), reacted with Zn(ii) to form 3,3-connected undulating hexagonal sheets based on tetrahedral P and Zn nodes, where Zn-ptbc = 1 : 1. When hydroxide was used as an additional framework ligand, Zn(4)(OH)(2) clusters were obtained. The clusters support 6,3-connected bilayers that consist of pairs of fused hexagonal sheets (Zn-ptbc = 2 : 1) with intra-layer pore spaces. The Zn(4)(OH)(2) clusters are also coordinated by solvent, which was preferentially displaced when the bilayer material was synthesized in the presence of ethylene diamine. Treatment of ptbc(3-) with MeI resulted in methylation of the phosphine to give the P(v) phosphonium iodide salt derivative. The formally dianionic methylphosphonium tricarboxylate building block, mptbc(2-), has the same trigonal-pyramidal bridging geometry as the parent phosphine. However, mptbc(2-) reacted with Zn(ii) on a 1 : 1 stoichiometric ratio to give an unusual trilayer sheet polymer that is based exclusively on 3-connected nodes. Solid-state (31)P NMR studies confirmed that the phosphine ligands were resistant to oxidation upon solvothermal reaction under aerobic conditions.

Zirconadihydrophosphetes as highly active species for ethylene polymerization

The zirconadihydrophosphetes showed high activities for ethylene polymerization as well as copolymerization with α-olefins or norbornene in the presence of methylaluminoxane (MAO) as cocatalyst. The alkylated intermediates as the active species were confirmed by NMR measurement. The cause for their high catalytic activities is assumed to the disassociation and coordination of the ethylene-bridged phosphine to the zirconium species. A plausible mechanism for the polymerization is proposed.

Synthesis and Reactivity of Tantalum Complexes Supported by Bidentate X2 and Tridentate LX2 Ligands with Two Phenolates Linked to Pyridine, Thiophene, Furan, and Benzene Connectors: Mechanistic Studies of the Formation of a Tantalum Benzylidene and Insertion Chemistry for Tantalum−Carbon Bonds

Using either alkane elimination or salt metathesis methods, tantalum complexes have been prepared with new ligand systems with tridentate bis(phenolate)donor (donor = pyridine, furan, and thiophene) or bidentate bis(phenolate)benzene arrangements. The ligand framework has two X-type phenolates connected to the flat heterocyclic L-type donor at the 2,6- or 2,5- positions or to the 2,6- positions of benzene via direct ring−ring (sp_2−sp_2) linkages. Solid-state structures of these complexes show that in all cases the ligands bind in a mer fashion, but with different geometries of the LX_2 frameworks. The pyridine-linked system binds in a Cs-fashion, the furan-linked system in a C2_v-fashion, and the thiophene-linked system in a C_1-fashion. A bis(phenolate)pyridine tantalum tribenzyl species (7), upon heating in the presence of dimethylphenylphosphine, generates a stable benzylidene complex by α-hydrogen abstraction with loss of toluene and PMe_2Ph trapping. This process was found to be independent of PMe_2Ph concentration with ΔH = 31.3 ± 0.6 kcal·mol−1 and ΔS = 3 ± 2 cal·mol−1·K−1, and the kinetic isotope effect kH/kD = 4.9 ± 0.4, consistent with a mechanism involving rate determining α-hydrogen abstraction with loss of toluene, followed by fast phosphine coordination to the resulting benzylidene species. An X-ray structure determination reveals that the benzylidene π-bond is oriented perpendicular to the oxygen−oxygen vector, in accord with the prediction of DFT calculations. Tantalum alkyl complexes with the benzene-linked bis(phenolate) ligand (Ta(CH_3)2[(OC_6H_2-tBu_2)2C_6H_3] (16), Ta(CH_2Ph)2[(OC_6H_2-tBu_2)2C_6H_3] (17), and TaCl_2CH_3[(OC_6H_2-tBu_2)2C_6H_4] (18)) are obtained with (to afford pincer complexes) or without cyclometalation at the ipso-position. Deuterium labeling of the phenol hydrogens and of the linking 1,3-benzene-diyl ring reveals an unexpected mechanism for the metalation of bis(phenol)benzene with TaC_l2(CH_3)3 to generate 18. This process involves protonolysis of a methyl group, followed by C-H/Ta-CH_3 σ bond metathesis leading to cyclometalation of the linking ring, and finally protonation of the cyclometallated group by the pendant phenol. TaCl_2CH_3[(OC_6H_2-tBu_2)2C_6H_4] was found to undergo σ bond metathesis at temperatures over 90 °C to give the pincer complex TaCl_2[(OC_6H_2-tBu_2)2C_6H_3] (1_9) and methane (ΔH = 27.1 ± 0.9 kcal·mol−1; ΔS≠ = −2 ± 2 cal·mol^1·K^1; k_H/k_D = 1.6 ± 0.2 at 125 °C). Ta(CH_3)_2[(OC_6H_2-tBu_2)_2C_6H_3] (16) was found to react with tBuNC to insert into the Ta-CH_3 bonds and generate an imino-acyl species (23). Reaction of 16 with Ph_2CO or PhCN leads to insertion into the Ta-Ph bond to give 21 and 22. Complexes 6, 7, 10, 11-P, 12, 13, 17, 18, 19-OEt_2, 21, 22, and 23 have been structurally characterized by single crystal X-ray diffraction, and all show a mer binding mode of the diphenolate ligands, but the ligand geometry varies leading to C_2v-, pseudo-C_s-, pseudo-C_2-, and C_1-symmetric structures.

Synthesis and Catalytic Properties of Rhodium(I) and Copper(I) Complexes Bearing Dipyrido-Annulated N-Heterocyclic Carbene Ligands

Starting from the in situ generated free carbenes dipyrido[1,2-c;2′,1′-e]imidazolin-6-ylidene (dipiy) and 2,10-di-tert-butyldipyrido[1,2-c;2′,1′-e]imidazolin-6-ylidene (dipiytBu), the synthesis of the new carbene complexes [RhCl(COD)(dipiy)] and [RhCl(COD)(dipiytBu)] can be achieved. Upon chloride abstraction and coordination of phosphine, a very active precursor for the catalytic hydrosilylation of ketones is formed. The reaction was also followed by NMR spectroscopy. In addition the respective CuI(dipiytBu) complex was synthesized and fully characterized. X-ray structure analysis reveals this compound to be a trimer [CuI(dipiytBu)]3 with two Cu−Cu bonds in the solid state. However, unlike the imidazolinylidene analogues, this complex and in situ prepared CuX(dipiy) complexes (X = I, Cl) were found to be inactive in the hydrosilylation of ketones.

The Coordination and Derivative Chemistry of Phosphinoalkynes on Polymetallic Frameworks and Related Systems

Some aspects of the coordination chemistry of phosphinoalkynes on polymetallic cluster frameworks are reviewed and illustrated with selected examples. Topics covered include the preparation of phosphinoalkynes, alkyne coordination, phosphine coordination, coordination in the absence of P–C bond cleavage, P–C bond cleavage and subsequent transformations of the resulting acetylide ligands, and the use of metal complexes of phosphinoalkynes as metalloligands in catalytic applications.

Broad HOMO–LUMO gap tuning through the coordination of a single phosphine, aminophosphine or phosphite onto a Ru(tpy)(bpy)2+ core

The synthesis of new ruthenium(II) terpyridine bipyridine complexes bearing a phosphorus(III) ligand is presented. The steric and electronic properties of the phosphorus ligand were varied using aminophosphines, alkyl and aryl phosphites and the bulky tri(isopropyl)phosphine. All complexes were characterized by multi-nuclear NMR spectroscopy, mass spectrometry and X-ray diffraction analysis. The electronic properties of the complexes were probed by cyclic voltammetry, absorption and luminescence spectroscopy. The complexes do not show luminescence at room temperature, whereas at 77 K in an alcoholic matrix, emission is observed in the range 600-650 nm with lifetimes of 3.5-5.5 micros, originating from 3MLCT states. The MLCT transition spans over 65 nm, which corresponds to a variation of 0.4 eV in the HOMO-LUMO gap. The oxidation potential of the ruthenium varies over a broad range of 290 mV, from +1.32 V vs. SCE with L = PiPr3 to +1.61 V vs. SCE with L = P(OPh)3. This range is unprecedented upon the variation of a single monodentate ligand coordinated by the same heteroatom in the same oxidation and charge states. This work underlines the specific capacity of phosphorus in bringing up a large variety of electronic properties by changing its substituents.

Contrasting arsine and phosphine coordination behaviour: heteroleptic palladium(II) complexes with triphenylarsine and a crown thioether

The synthesis, spectroscopic data and crystal structures of two new mononuclear Pd(II) heteroleptic complexes with the crown trithioether 1,4,7-trithiacyclononane (9S3) and the arsine ligand, triphenylarsine (AsPh3) are presented. Reaction between [Pd(9S3)Cl2] and AsPh3 (1:2 stoichiometry) in nitromethane followed by metathesis to the hexafluorophosphate salt results in the formation of two different palladium(II) complexes, the expected bis arsine complex [Pd(9S3)(AsPh3)2](PF6)2 as well as, surprisingly, the intermediate mono arsine-chloro complex [Pd(9S3)(AsPh3)(Cl)](PF6). Both complexes exhibit the anticipated structure consisting of a cis square planar array of two sulfur atoms from the 9S3 and either two As donors (bis AsPh3 complex) or one As and one Cl donor (mono AsPh3 complex). The third 9S3 sulfur atom exhibits a long distance interaction with the palladium forming an elongated square pyramidal geometry with a coordination environment around the Pd best described as [S2As2 + S1] or [S2AsCl + S1]...

Preparation of Tungsten Alkyl Alkylidene Alkylidyne Complexes and Kinetic Studies of Their Formation

An equilibrium mixture of alkyl alkylidyne W(CH2SiMe3)3(CSiMe3)(PMe3) (1a) and its bis(alkylidene) tautomer W(CH2SiMe3)2(=CHSiMe3)2(PMe3) (1b) has been found to undergo an alpha-hydrogen abstraction reaction in the presence of PMe3 to form alkyl alkylidene alkylidyne W(CH2SiMe3)(=CHSiMe3)(CSiMe3)(PMe3)2 (2). In the presence of PMe3, the formation of 2 follows first-order kinetics, and the observed rate constant was found to be independent of the concentration of PMe3. The activation parameters for the formation of 2 are Delta H = 28.3(1.7) kcal/mol and Delta S = 3(5) eu. In the presence of PMe2Ph, an equilibrium mixture of W(CH2SiMe3)3(CSiMe3)(PMe2Ph) (3a) and its bis(alkylidene) tautomer W(CH2SiMe3)2(=CHSiMe3)2(PMe2Ph) (3b) was similarly converted to W(CH2SiMe3)(=CHSiMe3)(CSiMe3)(PMe2Ph)2 (4). The observed rate of this reaction was also independent of the concentration of PMe2Ph. These observations suggest a pathway in which the tautomeric mixtures 1a,b and 3a,b undergo rate-determining, alpha-hydrogen abstraction, followed by phosphine coordination, resulting in the formation of the alkyl alkylidene alkylidyne complexes 2 and 4.

Quantification of Ultrasound‐Induced Chain Scission in PdII–Phosphine Coordination Polymers

A kinetically inert, reversible coordination polymer (3) was obtained through complexation of dicyclohexylphosphine telechelic poly(tetrahydrofuran) with palladium(II) dichloride. This coordination polymer is unreactive towards palladium(II) dichloride bis(1-diphenylphosphino)dodecane (4), because ligand dissociation in the coordination polymer is slow. However, upon ultrasonication of solutions of 3 in toluene in the presence of 4, formation of palladium(II) heterocomplexes was observed with (31)P NMR spectroscopy. Heterocomplex formation, the consumption of 4, and changes in molecular weight were used to quantify the scission process. In the presence of 60 equivalents of the alkyldiphenylphosphine stopper complex, the reduction in molecular weight was strongly enhanced; over a period of eight hours the weight-averaged molecular weight was reduced from 1.1x10(5) to 2.3x10(4) g mol(-1) while 47 % of the palladium(II) complexes in the coordination polymer had been converted into heterocomplexes. These results show that the system of 3 in combination with scavenger 4 is a suitable system to study the efficiency of ultrasound-induced chain scission of coordination polymers.

Rhenium chemistry of pyridyldiazoles : oxygen atom transfer, oxidation, substitution and twin isomerization involving oxo, phosphine oxide and phosphine coordination

The pyridyldiazoles (L) used are 2,5-bis(2-pyridyl)-1,3,4-oxadiazole and 2,5-bis(2-pyridyl)-1,3,4-thiadiazole. The oxygen atom transfer reaction of [ReOCl 3 (L)] with PPh 2 R (R = Ph, Me) and Ph 2 P(CH 2 ) x PPh 2 (PxP, x = 1-4) has afforded meridional [Re(OPPh 2 R)Cl 3 (L)] and [Re(OPxP)Cl 3 (L)] respectively. These (R = Ph, x = 1) are oxidised by HNO 3 yielding [Re(OPPh 3 )Cl 3 (L)]Re0 4 and [Re(OPlP)Cl 3 (L)]Re0 4 . Treatment of [Re(OPPh 2 R)Cl 3 (L)] with PPh 2 R has furnished facial [Re(PPh 2 R)Cl 3 (L)]. The [Re(OPxP)Cl 3 (L)] species undergo spontaneous twin isomerization in solution leading to [Re(PxPO)Cl 3 (L)]. All compounds have been characterized with the help of spectral and electrochemical data. The X-ray structure of a [Re(OPPh 3 )Cl 3 (L)]ReO 4 complex is reported. The rates and activation parameters of oxygen atom transfer and twin isomerization reactions have been determined and reaction models proposed.

Non‐racemic Tin(IV) Complexes Containing P‐chirogenic Phosphinomethylphenolate Ligands

AbstractThe chiral SnIV complexes L*SnMe2Cl (5) and L*SnMe2H (6) containing the P‐chirogenic o‐[(t‐butyl)(phenyl)phosphinomethyl]phenolate ligand (L*) have been synthesized via the respective lithium complex [LiL*]4 (4). The synthesis and structure of 4 are described. The stereochemical course of the ligand synthesis was monitored by chiral HPLC and single crystal structure analysis on suitable intermediates. The tin atom in 5 is pentacoordinate by intramolecular phosphine coordination whereas 6 contains tetracoordinate tin without phosphine coordination. Slow racemization of 5 at 100 °C afforded 5‐rac while oxidation with elemental oxygen led under retention of configuration at phosphorus to the phosphinoxide complex o‐[(tBu)(Ph)P*(O)CH2]C6H4OSnMe2Cl (7) with P‐O coordination to tin. The compounds 5, 5‐rac, and 7 were also characterized by X‐ray diffraction.

Preparation and Catalysis of a Tri-coordinated Copper(I) Complex with Bulky P˜N Ligand

Coordination of a bulky pyridinyl-phosphine (P∼N) ligand toward CuBr was investigated. However, this P∼N donor behaves as a monodentate via the coordination of phosphine to form a bromide bridged dimeric [(P∼N)Cu(p-Br)2Cu(P∼N)], which was characterized by spectral and crystal structural analysis. It appeared that the PCu(μ-Br) 2 CuP unit is planar with a short distance between Cu...Cu' [2.7585(9) A]. The catalytic activity on Sonogashira coupling of phenylacetylene with aryl halides was studied.

A Comparison of Structure and Stability Between the Group 11 Halide Tetramers M4X4 (M: Cu, Ag, or Au; X: F, Cl, Br, or I) and the Group 11 Chloride and Bromide Phosphanes (XMPH3)4

AbstractFor Abstract see ChemInform Abstract in Full Text.

A comparison of structure and stability between the group 11 halide tetramers M4X4 (M = Cu, Ag, or Au; X = F, Cl, Br, or I) and the group 11 chloride and bromide phosphanes (XMPH3)4.

The tetramers of the group 11 (I) halides, M(4)X(4) (M = Cu, Ag, or Au; X = F, Cl, Br, or I), and corresponding group 11 (I) phosphanes, chloride and bromide (XMPH(3))(4) (X = Cl or Br), are investigated by the density functional theory. All coinage metal(I) halide tetramers adopt squarelike ring structures with an out-of-plane distorted (butterfly) D(2d) symmetry. These structures are much lower in energy than the more compact cubelike T(d) arrangements, which maximize dipole-dipole interactions and more closely resemble the solid-state structures of the copper and silver halides. Phosphine coordination completely changes the structures of these M(4)X(4) clusters. The copper(I) and silver(I) phosphane chloride and bromide tetramers adopt a heterocubane structure, slightly preferred over a step (ladder-type)-cluster structure well-known in the coordination chemistry of such compounds. In stark contrast, gold(I) phosphane chloride and bromide tetramers prefer assemblies of linear XAuPH(3) units with direct gold-gold contacts, resulting in a square planar, centered trigonal planar, or tetrahedral gold core.