Platinum Phosphine Complexes Research Articles

Platinum(II) complexes incorporating racemic and optically active 1-alkyl-3-phospholene P-ligands: Synthesis, stereostructure, NMR properties and catalytic activity

Three 1-alkyl-3-phospholene 1-oxides, such as the P-ethyl, P-isobutyl and P-isopentyl derivative were prepared in racemic and enantiopure forms. After deoxygenation, the cyclic phosphines were converted to the corresponding phosphine–boranes and phosphine–platinum complexes (PtCl2L2, where L = 1-alkyl-3-phospholene). The new products were characterized by spectral methods, and the stereostructure of the complexes was also evaluated by high level quantum chemical calculations. The platinum complexes were tested in the hydroformylation of the styrene. The extent of the regioselectivity towards branched aldehyde exceeds that measured with earlier platinum complexes. However, the enantioselectivity remained below 29%.

Supported platinum/tin complexes as catalysts for hydroformylation of 1-hexene in supercritical carbon dioxide

Platinum–phosphine complexes anchored on silica and on mesoporous MCM-41 supports were synthesized. Hydroformylation of 1-hexene was performed at 100 °C in supercritical carbon dioxide (pressure=2700 psi) using these supported platinum catalysts with SnCl 2 · 2H 2O (Sn:Pt=3.5:1) as co-catalyst. No hydrogenation was observed and high regioselectivity to heptanal was obtained.

Coordination chemistry of the water-soluble ligand TPPTP and formation of a [Mo(CO)5(m-TPPTP)] monolayer on an alumina surface.

Phosphonate and phosphonic acid functionalized phosphine complexes of platinum(II) were prepared via direct reaction of the ligands with K2PtCl4 in water. Either cis or trans geometries were found depending on the nature of the ligand. The crystal structure of P(3-C6H4PO3H2)3.2H2O (6b) (triclinic, P1, a = 8.3501(6) A, b = 10.1907(6) A, c = 14.6529(14) A, alpha = 94.177(6) degrees, beta = 105.885(6) degrees, gamma = 108.784(5) degrees, Z = 2) shows a layered arrangement of the phosphonic acid. The phosphonodiamide complex cis-[PtCl2(P[4-C6H4PO[N(CH3]2]]3)2].3H2O (10) was synthesized in 89% yield and hydrolyzed to the phosphonic acid complex using dilute HCl. Aqueous phase and silica gel supported catalytic phosphonylation of phenyl triflate using palladium phosphine complexes was achieved. A molybdenum complex, Mo(CO)5[P3-C6H4PO3H2)3] (11), was synthesized in situ and grafted to an alumina surface. XPS, RBS, and AFM studies confirm the formation of a monolayer of 11 on the alumina surface.

Synthesis, Structure, and Characterization of a Bridging Ethylidene (Perfluoroalkyl)phosphine Platinum Complex

Thermolysis of (dfepe)Pt(Et)(O2CCF3) (dfepe = (C2F5)2PCH2CH2P(C2F5)2) in benzene at 80 °C results in the formation of (dfepe)Pt(η2-C2H4). However, at 120 °C in CF3CO2H a bridging ethylidene platinum dimer, [(dfepe)2Pt2(μ-CHMe)(μ-H)][O2CCF3], is produced instead. Product isolation by precipitation with diethyl ether afforded the neutral dimer (dfepe)2Pt2(μ-CHMe3). Alternatively, (dfepe)2Pt2(μ-CHMe) may be prepared at 20 °C by treatment of [(dfepe)Pt(μ-H)]2(H)+ with 1 atm of ethylene. Complete characterization of this species was accomplished by 1H, 13C, and 31P NMR spectroscopy, as well as X-ray diffraction. Investigations probing the mechanism of formation for this μ-alkylidene product are presented. The synthesis of the benzyl complex (dfepe)Pt(CH2Ph)(O2CCF3) and its reversible rearrangement to the η3-benzyl complex [(dfepe)Pt(η3-CH2Ph)]+ upon labilization of trifluoroacetate anion is also reported.

A Simple Relativistic Correction to the Nuclear Spin−Spin Coupling Constant

We present two relativistic correction schemes to account for the relativistic effects on one-bond metal−ligand couplings. On the basis of the Pauli Hamiltonian, the first method is a direct analogue to the nonrelativistic spin−spin coupling approach. In the second method, however, only the s-orbital contraction of the coupling metal atom is taken into account in computing the Fermi-contact contribution. These schemes are applied to the calculation of metal−ligand reduced coupling constants 1K(M−L) in some group 4 and 12 hyrides, alkyl complexes, and cyano complexes, as well as some platinum ammine and platinum phosphine complexes. It is shown that the second approximate method, a refined version of the “hydrogen-like” relativistic correction suggested by Pyykko, gives greater improvement over the nonrelativistic values and agrees better with experiments. Finally, the connection between the trans influence and coupling constants is discussed in the context of some square-planar platinum complexes.

Reactions of organotin(IV) compounds with platinum complexes

Organotin(IV) compounds SnRxCl4−x (R=Me, Ph; x=4−0) add oxidatively to [Pt(COD)2] (COD=cycloocta-1,5-diene) to yield platinum(II) complexes in which Pt has inserted into the SnCl or SnR bonds, displacing one COD entity. The new complexes react with tertiary phosphines, e.g. PEt3, PPh3, Ph2PCH2CH2PPh2 (DPPE) at or below room temperature with displacement of the remaining COD. Some of the resulting platinum–phosphine complexes, e.g. cis-[PtMe(SnMe3)(PPh3)2], cis- or trans-[PtCl(SnMe3)(PPh3)2] cannot be prepared by the direct reaction between [Pt(C2H4)(PPh3)2] or [Pt(PPh3)3] and SnMe4 or SnMe3CI, respectively, showing the advantage of this method. Both the COD complexes and their corresponding phosphine complexes were characterised by physical and spectroscopic methods. The thermodynamic stabilities of the complex [PtCl(SnMe3)(COD)], its corresponding phosphine complex, cis- and trans-[PtCl(SnMe3)(PPh3)2], and the complex cis-[PtMe(SnMe3)(PPh3)2] were studied.

ChemInform Abstract: Organometallics in Acidic Media: Catalytic Dimerization of Ethylene by (Perfluoroalkyl)phosphine Complexes of Platinum and Palladium in Trifluoroacetic Acid.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Organometallics in Acidic Media: Catalytic Dimerization of Ethylene by (Perfluoroalkyl)phosphine Complexes of Platinum and Palladium in Trifluoroacetic Acid

Catalytic ethylene dimerization by (dfepe)Pt(Me)X complexes in aprotic and trifluoroacetic acid solvents is described. In CH2Cl2, catalyst deactivation due to acid loss and generation of (dfepe)Pt(η2-C2H4) is observed. In contrast, long-term ethylene dimerization activity takes place in trifluoroacetic acid at 80 °C and produces 2-(trifluoroacetato)butane as the sole organic product. Under these reaction conditions, the catalyst resting state is (dfepe)Pt(Et)(O2CCF3). At 20 °C, reversible acid elimination from (dfepe)Pt(Et)(O2CCF3) and ethylene ligand exchange results in catalytic vinylic H+/D+ exchange with CF3CO2D (t1/2 ≈ 40 min). Analogous palladium systems exhibit enhanced dimerization activity at 25 °C (340 turnovers/h, 100 psi C2H4) and form (dfepe)2Pd as a catalyst resting state. Inhibition of catalytic activity in the presence of added dfepe was noted. Comparisons between catalytic runs in CF3CO2H and CF3CO2D gave an apparent solvent kinetic effect of 3.5(2), based on an initial second-order rate ...

Addition of Methanol to Nonactivated Internal Alkynes Catalyzed by Dichloro(diphosphine)platinum(II) Complex/Silver Salt Systems

Nucleophilic addition of methanol to nonactivated alkynes is catalyzed by platinum phosphine complexes derived from PtCl2(ligand) [ligand = 2PPh3, 2PPh2Me, diphos, dppt (1,5-bis(diphenylphosphino)pentane)] and a silver salt [AgPF6 or AgOTf (silver trifluoromethanesulfonate)] producing ketones in high yields. The catalytic activity is influenced by the phosphine ligand as well as by the anion and the ratio of the dichloroplatinum complex to the silver salt.

The nature of the platinum–phosphine bond. An ab initio Hartree–Fock and density functional study

The electronic structure of model complexes [Pt(PX3)2](X = H or F) has been investigated by ab initio calculations, carried out with several theoretical approaches, of different sophistication, based on the Hartree–Fock method and density functional theory. Density functional calculations including correlation and relativistic effects gave highly reliable theoretical values for the equilibrium geometries and stabilities of the complexes, more accurate than those previously reported. The best estimates of the Pt–P bond distances are 2.27 and 2.25 Å, for [Pt(PH3)2] and [Pt(PF3)2], respectively. The corresponding dissociation energies are 5.3 eV and 5.1 eV. The differences in chemical behaviour exhibited by PH3 and PF3 can be summarised as follows: the σ-donated charge from PX3 to the metal is found to be 0.12 and 0.39 electron, for X = H and F; the π-back-donated charge is 0.48 and 0.59, respectively. Therefore the PF3 ligand should be classified as a stronger σ donor and π acceptor than PH3, but its platinum complex is not more stable than [Pt(PH3)2]. The role of the polarisation functions centred on the ligand atoms should be interpreted more generally than that of the conventional σ-π mechanism, due to the fact that σ- and π-orbital occupancies are related not only to metal–ligand charge exchange but also to a charge rearrangement internal to the ligands, which cannot be fully interpreted in terms of a simplified orbital picture. Indeed, the whole electronic structure of the platinum phosphine complexes is largely dominated by electron correlation and relativistic effects.

ChemInform Abstract: Hydrophosphination of Formaldehyde Catalyzed by Tris(hydroxymethyl) phosphine Complexes of Platinum, Palladium or Nickel.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Hydrophosphination of formaldehyde catalysed by tris-(hydroxymethyl)phosphine complexes of platinum, palladium or nickel

The addition of PH3 to formaldehyde to give P(CH2OH)3 is catalysed by a range of platinum-(IV), -(II) and -(0) compounds including Na2[PtCl6], K2[PtCl4], [PtCl2{P(CH2OH)3}2]2 and [Pt{P(CH2OH)3}4]·H2O 3. A large ratio of P(CH2OH)3 to Pt is present under the conditions in which the catalysis is operated and the hypothesis that a common platinum–P(CH2OH)3 complex is present under these conditions has been tested. It is shown that Na2[PtCl6] is reduced by 3 equivalents of P(CH2OH)3 to give [PtCl2{P(CH2OH)3}2]2, the same species that is formed upon addition of 2 equivalents of P(CH2OH)3 to K2[PtCl4]. Addition of 1 equivalent of P(CH2OH)3 to 2 gives [PtCl{P(CH2OH)3}]3Cl 4a while addition of 2 equivalents of P(CH2OH)3 to 2 gives an unstable species, tentatively assigned the five-co-ordinate structure [PtCl{P(CH2OH)3}4]Cl 5a. In the presence of further P(CH2OH)3, 5a decomposes smoothly to give a mixture of [PtH{P(CH2OH)3}4]Cl 3b, [P(CH2OH)4]Cl and the unusual bis(chelate) salts trans- and cis-[Pt{(HOCH2)2PCH2OP(CH2OH)2}2]Cl26a and 6b. A mechanism rationalising this reaction is presented. The pH of the reaction medium during the catalysis is ca. 9–10 and it is therefore concluded that [Pt{P(CH2OH)3}4]3a is the main platinum-containing species present during all the platinum catalysed reactions. It is shown that [Ni{P(CH2OH)3}4]18 and [Pd{P(CH2OH)3}4]19 are also catalysts for the hydrophosphination of formaldehyde and a general mechanism is suggested.

Structural analysis of platinum phosphine complexes by two-dimensional phosphorus-31 NMR spectroscopy

The synthesis and characterization of a new platinum(I) phosphine complex, [Pt 2 (μ-dppm)(η 1 -dppm)dppeCl]Cl, (dppm=bis(diphenylphosphino)methane) , is reported. This unique complex is the first example of a stable Pt(I) dimer in which all three types of coordination possible for a diphosphine ligand are observed. To structurally characterize this complex, we have employed one- and two-dimensional 31 P NMR spectroscopy

The role of the d orbitals of the phosphorous atoms in the phosphine-platinum bond: an ab-initio study of Pt(PH3)2 and Pt(PH3)2(ŋ2O2) complexes

The role played by thed orbitals of the phosphorous atoms in stabilizing the Pt-P bond in platinum phosphine complexes is discussed on the basis of theoreticalab- initio results obtained for the complexes Pt(PH3)2 and Pt(PH3)2(ŋ2O2).

A new trifluorosilyl exchange reagent: reactions of Cd(SiF3)2·glyme (glyme = dimethoxyethane) with dibromo metal phosphine complexes of platinum, palladium, and nickel yield trifluorosilyl substituted dialkyl compounds

The reaction of excess Cd(SiF3)2·glyme (glyme = dimethoxyethane) with trimethylphosphine metal dibromides of platinum, palladium, and nickel yielded the trifluorosilyl substituted dialkyl compounds trans-Pt(SiF3)2(PMe3)2, Pd(SiF3)2(PMe3)2, and Ni(SiF3)2(PMe3)3.

ChemInform Abstract: PHOSPHORUS‐31 NUCLEAR MAGNETIC RESONANCE SPECTROSCOPIC STUDIES ON SOME ZEROVALENT PLATINUM PHOSPHINE COMPLEXES

Chemischer InformationsdienstVolume 12, Issue 18 Physical Organic Chemistry ChemInform Abstract: PHOSPHORUS-31 NUCLEAR MAGNETIC RESONANCE SPECTROSCOPIC STUDIES ON SOME ZEROVALENT PLATINUM PHOSPHINE COMPLEXES A.-R. AL-OHALY, A.-R. AL-OHALYSearch for more papers by this authorJ. F. NIXON, J. F. NIXONSearch for more papers by this author A.-R. AL-OHALY, A.-R. AL-OHALYSearch for more papers by this authorJ. F. NIXON, J. F. NIXONSearch for more papers by this author First published: May 5, 1981 https://doi.org/10.1002/chin.198118064Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume12, Issue18May 5, 1981 RelatedInformation

Oxidative addition of triorganostannanes to amine, phosphite and phosphine complexes of platinum

Triarylstannanes SnHR 3 react with the platinum (0) complexes [PtL 4] [L  P(OR′) 3,R′  Ph, C 6H 4Me-3 or -4] and [Pt(PPh 3)L 3] [L  P(OC 6H 4Me-3) 3] to give rans-[Pt(SnR 3) 2L 2], with the oxalato-platinum(II) complexes [Pt(C 2O 4)LL′] [L  L′  P(OPh) 3; L  PMe 2Ph, L′  P(OPh) 3; L  PET 3, L′  P(OPh) 3] to give rans-[Pt(SnR 3) 2LL′], with [Pt(CO 3)(BIPY)] (BIPY  2,2′-bipyridyl) to give stable platinum(IV) complexes cis-trans-[PtH 2(SnR 3) 2-(BIPY)], with [PtMe 2(BIPY)] to give cis-trans-[PtH(Me)(SnR 3) 2(BIPY)], and with cis-[PtMe 2(PMe 2Ph) 2] to give rans-[Pt(SnR 3) 2(PMe 2Ph) 2] or [PtH(Me)(SnR 3) 2(PMe 2Ph) 2], and with cis-[PtMe 2(PY)(PPh 3] (PY  pyridine) to give rans-[Pt(SnPH 3) 2(PPh 3)(PY)]. The results indicate that the stability of the platinum(IV) complexes increases with the ‘hardness’ of the bases L: P(OR) 3 < phosphines < BIPY. The reaction mixtures of SnHPh 3, and [PtMe 2(BIPY)] or [PtMe 2(PMe 2Ph) 2] catalyse homogeneously the formation of Sn 2Ph 6. The starting complexes and product complexes were characterised by elemental analysis, IR, 1H AND 31P-{ 1H} NMR spectroscopy.

Convenient one-step synthesis of substituted phosphine complexes of platinum(II) directly from hexachloroplatinic acid

Cis-[PtCl2(PPh3)2] and [PtCl2(PP)] (PP = Ph2P(CH2)1, 2 or 4 PPh2) are synthesized by treating H2[PtCl6]·H2O with an excess of phosphine in EtOH; by the same procedure, except for the presence of aqueous formaldehyde, trans-[PtCl2(PPh3)2] can be prepared. By pressuring H2[PtCl6]· 6H2O and an excess of PPh3 with carbon monoxide and molecular hydrogen in EtOH trans-[PtHCl(PPh3)2] is obtained; in the presence of propene, even without molecular hydrogen, trans-[PtCl(COPrn)(PPh3)2] forms. All the above complexes are prepared in good yield.

Restricted rotation and preferred conformations in tris(pentafluorophenyl)phosphine platinum(II) complexes; the mechanism of helicity reversal in a co-ordinated triarylphosphine

Variable temperature 19F and 31P n.m.r. studies of some tris(pentafluorophenyl)phosphine platinum complexes show restricted rotation at low temperatures about the Pt–P and C(1)–P bonds with a preferred conformation in which none of the C(1)–P bonds lie in the platinum co-ordination plane; the mechanism of helicity reversal of the propeller-shaped ligand is a two-ring flip.

Hydrosilylation of allylamine catalysed by platinum complexes

Chloroplatinic acid modified with triphenylphosphine, -arsine and -stibine, some platinum-alkene and platinum-phosphine complexes were found to be efficient catalysts for the addition of triethoxysilane to allylamine yielding γ- and β-aminopropyltriethoxysilane. All the catalysts exhibited higher activity and some also higher selectivity compared to chloroplatinic acid. The effect of reaction conditions and the catalyst upon the proportion of both isomeric adducts is reported.