Substituted Phosphine Ligands Research Articles

Synthesis, characterization, and electrochemistry of five diiron propane-1,3-dithiolate complexes with substituted phosphine ligands

In this paper, five diiron propane-1,3-dithiolate complexes containing substituted phosphine ligands were prepared and structurally characterized. Treatment of [Fe2(CO)6(μ-SCH2CH2CH2S)] (1) with a monophosphine ligand methyl diphenylphosphinite, ethyl diphenylphosphinite, 4-(dimethylamino)phenyldiphenylphosphine, tris(2-methoxyphenyl)phosphine, or tris(4-chlorophenyl)phosphine in the presence of Me3NO·2H2O as the decarbonylating agent gave the corresponding phosphine-substituted analogues [Fe2(CO)5(L)(μ-SCH2CH2CH2S)] [L = Ph2POCH3, 2; Ph2POCH2CH3, 3; Ph2P(4-C6H4 NMe2), 4; P(2-C6H4OCH3)3, 5; P(4-C6H4Cl)3, 6] in 73–93% yields. Complexes 2–6 have been characterized by elemental analysis, spectroscopy, and X-ray crystallography. Additionally, electrochemical studies have shown that 2–6 can catalyze the reduction of protons to H2 in the presence of HOAc.

Synthesis, structures and photophysical properties of Cu(I) phosphine complexes with various diimine ligands

A series of triphenylphosphine Cu(I) complexes with various diimine ligands, [Cu(N–N)(PPh3)2](ClO4) [N–N=dmp (2); Ph2Phen (3); Ph2dmp (4); dpq (5); dppz (6); phenCN (7); phenOH (8)] are synthesized by the ligand substitution reactions of [Cu(MeCN)4](ClO4) with 2moleequiv. of PPh3 ligand and 1.2moleequiv. of diimine ligand. {Cu(dpq)[P(XPh)3]2}(ClO4) [X=Me (5a); OMe (5b); Cl (5c)] and {Cu(phenOH)[P(XPh)3]2}(ClO4) [X=Me (8a); OMe (8b)] are also obtained by using various substituted phosphine ligands. These mixed-ligand complexes have been characterized using 1H and 31P NMR spectroscopy, IR spectroscopy, mass spectrometry and elemental analysis. Three of these complexes have been structurally characterized by X-ray crystallography. The photophysical and electrochemical properties of these complexes have been studied. These complexes exhibit MLCT phosphorescence with emission energy, lifetimes and quantum yields showing strong dependence on the nature of diimine and phosphine ligands. In particular, both the electronic and steric effects of the substituting groups in phosphine ligands are also found to affect the emission properties of the complexes. Our study provides structural-properties information for the future design of luminescent Cu(I) complexes.

Cationic gold clusters ligated with differently substituted phosphines: effect of substitution on ligand reactivity and binding.

We present a systematic study of the effect of the number of methyl (Me) and cyclohexyl (Cy) functional groups in monodentate phosphine ligands on the solution-phase synthesis of ligated sub-nanometer gold clusters and their gas-phase fragmentation pathways. Small mixed ligand cationic gold clusters were synthesized using reactions between pre-formed triphenylphosphine ligated (PPh3) gold clusters and monodentate Me- and Cy-substituted phosphine ligands in solution and characterized using electrospray ionization mass spectrometry (ESI-MS) and collision-induced dissociation (CID) experiments. Under the same experimental conditions, larger gold-PPh3 clusters undergo efficient exchange of unsubstituted PPh3 ligands for singly Me- and Cy-substituted PPh2Me and PPh2Cy ligands. The efficiency of reaction decreases with an increasing number of Me or Cy groups in the substituted phosphine ligands. CID experiments performed for a series of mixed-ligand gold clusters indicate that loss of a neutral Me-substituted ligand is preferred over loss of a neutral PPh3 ligand while the opposite trend is observed for Cy-substituted ligands. The branching ratio of the competing ligand loss channels is strongly correlated with the electron donating ability of the phosphorous lone pair as determined by the relative proton affinity of the ligand. The results indicate that the relative ligand binding energies increase in the order PMe3 < PPhMe2 < PPh2Me < PPh3 < PPh2Cy < PPhCy2 < PCy3. Furthermore, the difference in relative ligand binding energies increases with the number of substituted PPh(3-m)Me(m) or PPh(3-m)Cy(m) ligands (L) on each cluster. This study provides the first experimental determination of the relative binding energies of ligated gold clusters containing differently substituted monophosphine ligands, which are important to controlling their synthesis and reactivity in solution. The results also indicate that ligand substitution is an important parameter that must be considered in theoretical modeling of these complex systems.

ChemInform Abstract: Ion‐Tagged Phosphines as Ligands for Suzuki Coupling of Aryl Halides in a Phosphonium Ionic Liquid.

AbstractN‐substituted phosphine ligands are employed in the Suzuki‐Miyaura coupling of aryl chlorides and bromides with phenyl boronic acid in ionic liquid/water system.

Synthesis, characterization and structural determination of some nickel(II) complexes containing imido Schiff bases and substituted phosphine ligands

Some new tridentate ONN Schiff base complexes of [NiL(PR3)] (where L=Salicylidene2-amino4-nitrobenzene (L1), 5-BrSalicylidene2-amino4-nitrobenzene (L2), 5-NO2Salicylidene2-amino4-nitrobenzene (L3), 5-MeOSalicylidene2-amino4-nitrobenzene (L4) and 3-MeOSalicylidene2-amino4-nitrobenzene (L5), R=Bu and Ph (with L1)) were synthesised and characterized by IR, UV–Vis, 1H NMR spectroscopy and elemental analysis. The geometry of [NiL1(PPh3)] was determined by X-ray crystallography. It indicated that the complex had a planar structure and four coordinates in the solid state. The thermogravimetry (TG) and differential thermoanalysis (DTA) of the synthesized complexes were carried out in the range of 20–600°C, leading to the decomposition of L1–L3 type in three stages and of L4–L5 and [NiL1(PPh3)] type in four stages. Thermal decomposition of the complexes was closely the dependent upon the nature of the Schiff base ligands and proceeded via the first order kinetics.

Syntheses, structure characterisation and X-ray studies of some mono, di- and tri-substituted cluster complexes of Ru3(CO)12 substituted by bulky fluorinated phosphine ligands

Five trinuclear substituted complexes of the type Ru3(CO)11L, Ru3(CO)10L2 and Ru3(CO)9L3 were synthesised by the reaction of Ru3(CO)12 with fluorine substituted phosphine ligands, {P(C6H4F-m)3 and P(C6H4F-p)3}, using the radical anion catalysed method. The structures of the resulting clusters were elucidated by means of elemental analyses and spectroscopic methods, which included IR, 1H, 13C and 31P NMR spectroscopy. X-ray crystallographic studies of four of the complexes were carried out. In all the complexes, the ligand occupies an equatorial position due to steric reasons, and coordination of the ligand is observed only at the phosphorus atom. In the two monosubstituted complexes, Ru3(CO)11P(C6H4F-m)3 and Ru3(CO)11P(C6H4F-p)3, the effect of substitution resulted in an increase in the Ru–Ru distances. Out of the three Ru–Ru bonds, the one which is cis to the ligand is noticeably longer than the other two. The asymmetric unit of the disubstituted complex Ru3(CO)10{P(C6H4F-p)3}2 is composed of two molecules, A and B. As expected, the two phosphorus ligands are equatorially bonded to two different ruthenium atoms. The asymmetric unit of the trisubstituted complex is composed of one molecule of Ru3(CO)9{P(C6H4F-m)3}3 and one disordered solvent molecule. The structure consists of one triangular ruthenium complex in which each of the phosphorus ligands is equatorially bonded to three different ruthenium atoms. In the structure, disorder of the fluorine atoms is observed. Bond parameters, especially bond lengths and bond angles, are correlated to the structure and also are compared with the literature data of similar compounds.

The coordination chemistry of perfluorovinyl substituted phosphine ligands, a crystallographic and spectroscopic study. Co-crystallisation of both cis- and trans-isomers of [PtCl2{PiPr2(CFCF2)}2] within the same unit cell

The coordination chemistry of the perfluorovinyl phosphines PEt2(CF=CF2), P(i)Pr2(CF=CF2), PCy,(CF=CF2) and PPh(CF=CF2)2 to rhodium(I), palladium(II), and platinum(II) centres has been investigated. The electronic properties of the ligands are estimated based on v(CO) and 1J(Rh-P) values. X-Ray diffraction data for the square-planar Pd(II) and Pt(II) perfluorovinyl-phosphine containing complexes allow estimates of the steric demand for the series of ligands PPh2(CF=CF2), PEt2(CF=CF2), P(i)Pr2(CF=CF2), PCy2(CF=CF2) and PPh(CF=CF2)2 to be determined. The (CF=CF2) fragment is found to be more electron withdrawing than (C6F5) yet sterically less demanding. These ligands therefore provide a range of electron-neutral to phosphite-like electronic properties combined with a range of steric demands. This study also reveals that short intramolecular interactions from the metal centre to the beta-fluorine atom cis to phosphorus of the CF=CF2 groups are observed in all-trans square planar complexes of the ligands. Unusually, the complex [PtCl2{P(i)Pr2(CF=CF2)}2] crystallises with both cis- and trans-isomers present in the unit cell. It appears that co-crystallisation of both isomers occurs in order to maximise fluorous regions in the crystal packing, and the extended structure displays short fluorine-fluorine contacts. The generation of mixed geometries seems to be a phenomenon of crystallisation, as solution phase NMR studies reveal the presence of only the trans-isomer.

Transition-Metal Complexes with Nano-Sized Phosphine and Pyridine Ligands-Catalysis, Fluxional Behavior and Molecular Recognition

Nano-sized phosphine and pyridine ligands having tetraphenylphenyl-, m-terphenyl-, poly(benzylether) moieties were synthesized. These ligands showed a remarkable effect on homogeneous transition metal catalyzed reactions. Pd(II) complexes with tetraphenylphenyl substituted pyridine ligands show high catalytic activities for oxidation of ketones suppressing Pd black formation and maintains the catalytic activity for a long time. Rh(I) complex catalysts with m-terphenyl substituted phosphine ligands showed remarkable rate acceleration in the hydrosilylation of ketones. In addition, several phosphinocalixarene ligands were synthesized and their coordination studies with Pd(II), Pt(II), Ru(II), Ir(I), and Rh(I) metals were documented. Ir(I) and Rh(I) cationic complexes with a 1,3,5-triphosphinocalix[6]arene ligand showed dynamic behavior with size-selective molecular recognition.

Quantifying the electronic effect of substituted phosphine ligands via molecular electrostatic potential.

Values of the molecular electrostatic potential minimum (V(min)) corresponding to the lone pair region of several substituted phosphine ligands (PR(3)) have been determined at the DFT level. The V(min) value is proposed as a quantitative measure of the electronic effect of the PR(3) ligands. Good linear correlation between V(min) and Tolman electronic parameter of PR(3) has been obtained. V(min) is also proportional to the pK(a) values of the conjugate acids of PR(3), viz., [PR(3)H](+). Further, the DeltaE values of the reaction Ni(CO)(3) + PR(3) --> Ni(CO)(3)PR(3) and ScH(3) + PR(3) --> ScH(3)PR(3) are also linearly proportional to the V(min) values. However, if there is a strong metal to phosphorus pi-back-bonding, the DeltaE and V(min) do not fit to a line. It is also found that the standard reduction potential as well as the enthalpy change corresponding to the electrochemical couple eta-Cp(CO)(PR(3))(COMe)Fe(+)/eta-Cp(CO)(PR(3))(COMe)Fe(0) is linearly proportional to the V(min) values of PR(3). These correlations suggest that V(min) is a quantitative measure of the sigma-donating ability of the phosphine. It is hoped that, in phosphine-metal coordination chemistry, the V(min) based electronic parameter could be more advantageous than nu-CO and pK(a) based electronic parameters as it solely represents the inherent electronic property of the ligand.

Effects of phosphine substituents on CO and norbornene insertion rates into (P,N)–Pd–alkyl and –acyl bonds

The synthesis is described of (P,N)–PdMe(X) (P,N=R 2P- o-C 6H 4CH 2NMe 2 ( L1), Me 2N- o-C 6H 4CH 2–PR 2 ( L2), 1-(dimethylamino)-8-(R 2phosphino)naphthalene ( L3) with R 2=Ph 2 ( a), Cy 2 ( b), Me,Ph ( c, for L1 only); X=Cl, OTf) and cationic (P,N)–PdMe(L) + (L, MeCN, CO; anion, −B[3,5-Ph–(CF 3) 2] 4). The complexes react with CO to give (P,N)–Pd{C(O)Me}(X/L +) derivatives. Carbonylation is faster in complexes with the more basic phosphines of type 1, but slower in ligand type 2 and 3. Norbornene inserts slowly into the (P,N)–Pd–acetyl bond of the cationic borate complexes with L1– 3, and for L2 with X=Cl, OTf. Cationic palladium complexes with phenyl substituted phosphine ligands are more reactive toward CO/norbornene mixtures than those with cyclohexyl and complexes of L2 and L1 react faster than that of L3. The observed reactivity is described in terms of differences in CO insertion rates and a rate determining isomerization or trapping by norbornene of the intermediates, trans-P (P,N)–Pd{C(O)Me} + complexes.

?-Conjugated soluble palladium poly-ynes: Synthesis and fluorescence properties

Insertion of thiophene-2,5-diyl, or 1,4-phenylene into palladium poly-ynes by the polycondensation of dihalide complexes PdCl2(PR3)2 (R = Ph o γ n-butyl) with a di-yne monomer (obtained from the reaction of equimolar quantities of p-diethynyl-benzene with 2,5-diiodothiophene or 1,4-diiodobenzene) affords a series of palladium poly-ynes 1–6. The polymers/oligomers, soluble in common organic solvents, exhibit strong fluorescence at the excitation of UV-visible light at room temperature. The emission intensity of the polymers/oligomers with thiophene-2,5-diyl is 3–17 times stronger than that of the analogous polymers without thiophene-2,5-diyl. Polymers with phenyl substituted phosphine ligands emit stronger emission than those only with n-butyl phosphine ligands. The effects of molecular weight, ligands, solvents, and concentration on the fluorescence properties are also investigated. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1657–1665, 1997

A Density Functional Study of Metal-Ligand Bonding in [(PR(3))(2)M](+) and [PR(3)MCl] (M = Ag, Au; R = H, Me) Complexes.

Relativistic and nonrelativistic electronic structure calculations were carried out on [(PR(3))(2)M](+)and [PR(3)MCl] (M = Ag, Au; R = H, Me) complexes using the all-electron linear combination of Gaussian-type orbitals density functional (LCGTO-DF) method. The calculated relativistic metal-ligand bond lengths show good agreement with experimental values. The relativistic contraction of the M-P bonds in [(PR(3))(2)M](+) is about 8 and 22 pm for M = Ag and Au, respectively, resulting in Au-P bonds that are about 10 pm shorter than the Ag-P bonds in these species, in good agreement with recent crystallographic results for the cations [(PMes(3))(2)M](+) (M = Ag, Au). The relativistic contraction of the Au-Cl bond in [PR(3)AuCl] is significantly less than that of the Au-P bond, and this explains the experimentally observed differential Au-X and Au-P bond length contractions from [PR(3)AgX] to [PR(3)AuX]. The calculated relativistic bond lengths for corresponding PH(3) and PMe(3) complexes are very similar, confirming a previous conclusion that PH(3) is a good model for structural properties of larger tertiary phosphine ligands. However, the bond lengths for the PMe(3) complexes are all slightly longer than those for the corresponding PH(3) complexes, whereas the M-P dissociation energies are 20-40% higher for the PMe(3) complexes. These findings provide computational support for the concept of "longer but stronger bonds", which was recently proposed on the basis of experimental studies of transition metal complexes involving various substituted phosphine ligands.

A CoMFA Model of Steric and Electronic Effects of Phosphorus Ligands

AbstractThe method of comparative molecular field analysis (CoMFA) has been applied to a series of 6 reactions involving a transition‐metal center and a series of substituted phosphine ligands. A CoMFA analysis of parameters used in classical QSAR including the Tolman cone angle and Brown's steric parameter ER has also been performed. Provided that the dataset of compounds is carefully chosen and is sufficiently large, CoMFA can be used in place of traditional QSAR methods which have employed Tolman cone angles and carbon‐13 chemical shifts as parameters. The CoMFA results show that steric and electronic factors have comparable weight in determining chemical reactivity in the types of reactions considered.

Multinuclear high‐resolution solid‐state magnetic resonance studies of some platinum(II) complexes with phosphorus‐containing ligands

AbstractCross‐polarization, magic‐angle spinning NMR experiments have been carried out for nine square‐planar platinum(II) complexes, each with two substituted phosphine ligands. 13C and 13P (and, in some cases, 195Pt) nuclei were observed. The results reveal crystallographic non‐equivalence which, in one instance, is confirmed by subsequent X‐ray studies. Chemical shifts and coupling constants—(Pt,P), (Pt,C), (P,C) and, for one compound, (Sn,P)—are reported and discussed. Shielding tensor data are also presented.

ChemInform Abstract: CRYSTAL STRUCTURE STUDIES OF HYDRAZIDO(2‐)QUINOLIN‐8‐OLATO COMPLEXES OF MOLYBDENUM AND TUNGSTEN

AbstractDie Molekül‐ und Kristallstrukturen der Komplexe (I) werden mittels Röntgendiffraktionsmethoden bestimmt.

Some manganese(I) complexes with multidentate substituted phosphine ligands

The potentially quadridentate ligand tris-(o-diphenylphosphinophenyl)phosphine (QP) reacts with various manganese(I) carbonyl compounds to give manganese(I) complexes in which the ligand acts as a bidentate, [MnX(CO)3(QP)], terdentate, [Mn(CO)3(QP)]+, or quadridentate, [Mn(CO)2(QP)]+, chelating agent. This has been substantiated by infrared studies and by the preparation and study of complexes of bis-(o-diphenylphosphinophenyl)phenylphosphine (TP) and of o-phenylenebisdiphenylphosphine (DP), which give compounds of the type [Mn(CO)3(TP)]+ and [MnX(CO)3(DP)], respectively. Manganese(II) complexes of QP could not be prepared either by oxidation of the manganese(I) complexes or by direct interaction of manganese(II) halides and the ligand. The preparation and infrared spectrum of cyanopentacarbonylmanganese(I), [Mn(CN)(CO)5], is reported.