Basic Phosphine Research Articles

Anomalous reactivity of triphenylarsine and triarylphosphines of low basicity with [Ir(cod)(py) 2][PF 6] and use of the complexes as precatalysts for imine hydrogenation

Reaction of [Ir(cod)(py) 2][PF 6] with PPh 3 or P(C 6H 4-4-F) 3 gives the bis(phosphine) derivative [Ir(cod)L 2][PF 6], but with the poorly basic phosphine P(C 6H 4-4-CF 3) 3 or AsPh 3 the mixed ligand complexes [Ir(cod)L(py)][PF 6] are obtained. The synthesis of [Ir(AsPh 3)(cod)(PPh 3)][CF 3SO 3] is described, and the structures of this and of [Ir(AsPh 3)(cod)(py)][PF 6] determined by X-ray crystallography. The use of some of the complexes as catalysts for imine hydrogenation is described.

Coordination chemistry of organometallic polydentate ligands Studies on the syntheses and properties of FeM binuclear complexes prepared from organometallic tridentate ligand trans-Fe(CO) 3(Ph 2Ppy) 2 (Ph 2Ppy = 2-(diphenylphosphino)pyridine)

The binuclear complexes (CO) 3Fe( μ-Ph 2Ppy) 2MX n (Ph 2Ppy = 2-(diphenylphosphino)pyridine, MX n = Mn(SCN) 2, Co(SCN) 2, CoCl 2, NiCl 2, Mo(CO) 3, Zn(SCN) 2, ZnCl 2, Cd(SCN) 2, CdCl 2, HgCl 2, HgI 2, AgClO 4, and SnCl 2) were prepared from the new type of organometallic tridentate ligand, trans-Fe(CO) 3(Ph 2Ppy) 2 ( 1), which contains both a basic metal center and bridging phosphine ligands. The crystal structure of the benzene solvate of 1 was determined by X-ray diffraction. The compound 1·1/2C 6H 6 crystallizes in the monoclinic space group P2 1/ c with a = 17.560(5), b = 12.110(1), c = 18.176(4) A ̊ ; β = 101.27(2)° and Z = 4 . The structure was refined to a conventional R value of 0.077 by using 2670 significant reflections and parameters. The structure of one of the binuclear complexes, namely, (CO) 3Fe(μ-Ph 2Ppy) 2HgI 2 ( 14), has also been determined by X-ray diffraction. The compound 14 crystallizes in the monoclinic space group P2 1/ n, with a = 13.829(2), b = 14.175(2), c = 19.514(3) A ̊ , β = 120.27(1)°, V = 3738(2) A ̊ 3 and Z = 4 . The structure was refined to a conventional R values of 0.032 by using 3279 significant reflections and parameters. The FeHg distance is 2.678 Å, indicative of a metal-metal bond. Results of Mössbauer and electron-absorption spectra suggested the presence of metal to metal interactions in these binuclear complexes.

Reactions of di- and tri-nuclear palladium and platinum isocyanide complexes with highly basic and bulky aromatic phosphines containing methoxy groups at the 2 and 6 positions

Reactions of [M2(RNC)6]2+(M = Pd 1 or Pt 3)(R = 2,6-Me2C6H3) with L = tris(2,6-dimethoxyphenyl)phosphine, bis(2,6-dimethoxyphenyl)phenylphosphine or (2,6-dimethoxyphenyl)diphenylphosphine gave [M2(RNC)4L2]2+(M = Pd 2 or Pt 4). Reaction of the neutral complex [Pd2Cl2(RNC)4]5 with P[C6H3(OMe)2]3 gave [Pd2(RNC)4{P[C6H3(OMe)2]3}2]Cl26c. A similar reaction in the presence of NH4PF6 gave 2c{L = P[C6H3(OMe)2]3} and trans-[PdCl(RNC)2{P[C6H3(OMe)2]3}]+7c. Compound 7c was obtained from the secondary reaction of 2c with NH4Cl formed initially. The structure was confirmed by an X-ray analysis. The trinuclear complex [Pt3(RNC)8]2+ reacted with the phosphines to give corresponding [Pt3(RNC)6L2]2+. A similar reaction of [Pd3(RNC)8]2+ with PPh2[C6H3(OMe)2] or PPh[C6H3(OMe)2]2 produced the corresponding [Pd3(RNC)6L2]2+, whereas with P[C6H3(OMe)2]3 cleavage of metal–metal bonds occurred to give only 2c.

Carbonylation of hydrocarbylpalladium(II) complexes containing substituted pyridinecarboxylate chelating ligands. Steric and electronic manipulation of the CO-insertion mechanism

Organopalladium(II) complexes of general formula [PdR(N–O)L][R = Ph, N–O = pyridinecarboxylate (pyca), L = P(C6H11)3; R = Ph, N–O = 6-methylpyridinecarboxylate (mpyca), L = PPh3, PMePh2, P(C6H11)3 or PEt3; R = Ph, N–O = 4-nitropyridinecarboxylate (npyca), L = P(C6H11)3; R = Ph, N–O = 6-methyl-4-nitropyridinecarboxylate, L = P(C6H11)3; R = Me, N–O = mpyca, L = PPh3, P(CH2Ph)3 or P(C6H11)3; R = Me, N–O = npyca, L = PPh3, PMePh2 or P(C6H11)3] have been prepared, and their carbonylation reactions studied in detail. Kinetic studies of the CO-insertion process have indicated that the rate of reaction decreases as the basicity of the phosphine, L, increases. Complexes containing the highly basic phosphine P(C6H11)3 only undergo carbonylation if hemilability of the chelating ligand is promoted (by substitution of the N–O chelate). Substitution of the N–O ligand modifies the carbonylation pathway and provides an alternative route from that generally observed for palladium(II) and platinum(II) hydrocarbyl complexes of pyca. A mechanism for insertion of CO involving partial dissociation of the N–O chelate is proposed for these complexes. The crystal stucture of [PdMe(mpyca)(PPh3)] has been determined. The complex has square-planar co-ordination with the nitrogen of pyca trans to the phosphorus. Considerable distortion of the inner co-ordination sphere is evident, caused by steric interaction between the σ-methyl ligand and the methyl group on the N–O ligand.

Effects of Cyclopentadienyl and Phosphine Ligands on the Basicities and Nucleophilicities of Cp‘Ir(CO)(PR3) Complexes

Basicities of the series of complexes CpIr(CO)(PR(3)) [PR(3) = P(p-C(6)H(4)CF(3))(3), P(p-C(6)H(4)F)(3), P(p-C(6)H(4)Cl)(3), PPh(3), P(p-C(6)H(4)CH(3))(3), P(p-C(6)H(4)OCH(3))(3), PPh(2)Me, PPhMe(2), PMe(3), PEt(3), PCy(3)] have been measured by the heat evolved (DeltaH(HM)) when the complex is protonated by CF(3)SO(3)H in 1,2-dichloroethane (DCE) at 25.0 degrees C. The -DeltaH(HM) values range from 28.0 kcal/mol for CpIr(CO)[P(p-C(6)H(4)CF(3))(3)] to 33.2 kcal/mol for CpIr(CO)(PMe(3)) and are directly related to the basicities of the PR(3) ligands in the complexes. For the more basic pentamethylcyclopentadienyl analogs, the -DeltaH(HM) values range from 33.8 kcal/mol for the weakest base CpIr(CO)[P(p-C(6)H(4)CF(3))(3)] to 38.0 kcal/mol for the strongest CpIr(CO)(PMe(3)). The nucleophilicities of the Cp'Ir(CO)(PR(3)) complexes were established from second-order rate constants (k) for their reactions with CH(3)I to give [Cp'Ir(CO)(PR(3))(CH(3))](+)I(-) in CD(2)Cl(2) at 25.0 degrees C. There is an excellent linear correlation between the basicities (DeltaH(HM)) and nucleophilicities (log k) of the CpIr(CO)(PR(3)) complexes. Only the complex CpIr(CO)(PCy(3)) with the bulky tricyclohexylphosphine ligand deviates dramatically from the trend. In general, the pentamethylcyclopentadienyl complexes react 40 times faster than the cyclopentadienyl analogs. However, they do not react as fast as predicted from electronic properties of the complexes, which suggests that the steric size of the Cp ligand reduces the nucleophilicities of the CpIr(CO)(PR(3)) complexes. In addition, heats of protonation (DeltaH(HP)) of tris(2-methoxyphenyl)phosphine, tris(2,6-dimethoxyphenyl)phosphine, and tris(2,4,6-trimethylphenyl)phosphine were measured and used to estimate pK(a) values for these highly basic phosphines.

Synthesis of Nitridoosmium(VI) Phosphine Complexes

Organoosmium(VI) complexes of PMe 3 , PPh 3 , and Ph 2 PCH 2 CH 2 PPh 2 (dppe) have been prepared and characterized. Unlike inorganic complexes of nitridoosmium(VI), the alkyl complexes are not reduced by basic phosphines. The reactions of [NBu 4 ] [Os(N) (CH 2 SiMe 3 ) 4 ] with HBF 4 in the presence of either PMe 3 or PPh 3 produces Os(N)(CH 2 -SiMe 3 ) 3 (PR 3 ). The addition of either PMe 3 or dppe to [NBu 4 ] [Os(N)(CH 2 SiMe 3 ) 2 Cl 2 ] produces Os(N)(CH 2 -SiMe 3 ) 2 L 2 Cl (L=PMe 3 , 1/2 dppe)

Decarbonylation of formate esters by amines and phosphines.

Some phophines and aliphatic amines are efficient in decarbonylating formate esters. Simple amines in the presence of DMF as well as some aminoalcohols decarbonylate methyl formate efficiently at 190°C. Likewise, formate esters are decarbonylated by very basic phosphines (P(CY) 3 and P(iPr) 3) without any metallic species at 180°C to form the corresponding alcohol and carbon monoxide.

Molybdenum-mercury bond. NMR (199Hg, 31P, 1H) and IR study on[(C5H5)(CO)2LMoHgZ] (LP(4-X-C6H4)3 (XF, Cl, Me, OMe), P(CH2CH3)3, P(CH2CH2CN)3; ZCl, I, (C5H5)(CO)2LMo) complexes

IR and multinuclear NMR studies, and in particular those of 199Hg NMR, have been carried out on the title molybdenum-mercury bonded complexes of the type Cp(CO)2(phosphine)MoHgZ. It is found that the 199Hg chemical shifts correlate well with the pKa values and with some electronic parameters, like Hammet's σ p or Bartik's FTχ, for para-substituted triphenyl phosphines and for PEt3. Less basic phosphines give rise to a shielding of mercury nuclei. A particular behaviour of P(CH2CH2CN)3 derivatives is ascribed to a possible intramolecular MoPCH2CH2CN → Hg interaction. The 2J(HgP) coupling constants do not exhibit a clear dependence either on the nature of the para-substituent in triarylphosphines or on the pKa values of the phosphorus ligand involved but do show a good linear correlation with the values of Tolman's θ cone angles: the higher the cone angle is, the lower is the coupling constant.

Kinetics of conversion of [Ir4(CO)11(PPh2AuPPh3)] into [Ir4(CO)10(µ-PPh2)(µ-AuPPh3)] and their structural characterization

Deprotonation of [Ir4(CO)11(PPh2H)]1 in the pressence of [Au(PPh3)]PF6 yields the novel species [Ir4(CO)11(PPh2AuPPh3)]2 which possesses a tetrahedral framework bearing a terminally bonded PPh2AuPPh3 ligand. Changing the order of addition of the reagents results in the formation of [Ir4(CO)10(µ-PPh2)(µ-AuPPh3)]4 with bridging phosphido and Au(PPh3)+ units. Reaction of 4 with PPh3 yields [Ir4(CO)9(PPh3)(µ-PPh2)(µ-AuPPh3)]6, while with the more basic phosphine P(C6H4OMe-4)3 substitution of the PPh3 at the Au(PPh3)+ unit occurs producing [Ir4(CO)10(µ-PPh2){µ-AuP(C6H4PMe-4)3}]. Deprotonation of [Ir4(CO)10(PPh3)(PPh2H)] in the presence of [Au(PPh3)]PF6 yields [Ir4(CO)10(PPh3)(PPh2AuPPh3)], which undergoes rearrangement to 6. The kinetics of decarbonylation of compound 2 and give 4 has been investigated and a dissociative mechanism is suggested, confirmed by the activation parameters ΔH‡= 135.6 ± 3.8 kJ mol–1 and ΔS‡= 81.2 ± 10.9 J K–1 mol–1.

Übergangsmetall-Silyl-Komplexe: XL. Umsetzung von cis-Fe(CO) 4(SiCl 3− nMe n) 2 ( n = 1−3) mit Phosphinen: Konkurrenz von CO-Substitution, SiR 3-Abspaltung und Bildung zweikerniger, SiR 2-verbrückter Komplexe

Upon reaction of benzene solutions of the bissilyl complexes cis-Fe(CO) 4(SiCl 3− n Me n ) 2 ( n = 1−3) with triphenylphosphine no disilane elimination takes places. Instead, formation of phosphine-substituted bissilyl or hydrido silyl complexes, disiloxanes and Fe(CO) 5− n (PPh 3) n ( n = 1, 2) is observed. The kind of products and their relative amounts strongly depend on the substituents at silicon. The influence of the phosphine is shown for reactions of cis-Fe(CO) 4(CiCl 3) 2 ( 1d): with PPh 3 or PMePh 2 only the phosphine-substituted derivatives Fe(CO) 3(PR 3)(SiCl 3) 2 are formed, while the more basic phosphines PMe 2Ph or PMe 3 give the SiCl 2-bridged dinuclear complexes Fe 2(CO) 8− n (PR 3) n (μ-SiCl 2) 2 (PMe 2Ph: n = 2; PMe 3: n = 1, 2) instead. The formation of SiR 2-bridged complexes in the reaction of Fe(CO) 4(SiR 3) 2 with phosphines is restricted to the SiCl 3 derivative.

Substituent effects on the alkyl migration reaction in pentacarbonylbenzylmanganese(I) systems

The k1 step of the formal insertion of carbon monoxide into a MnC σ bond in the reaction of substituted benzylmanganese complexes, [(CO)5MnCH2C6H5-nXn], with tertiary phosphines in acetonitrile is enhanced by electron-donating substituents in meta- and para-positions. Ortho-substitution by a methyl group causes a reduction in k1 compared with para-methyl substitution but di-substitution and single ortho-substitution by large alkyl groups increases reactivity. Similar behaviour occurs with Cl, F and CF3 as ortho-substituents. The value of k-1/k2, which reflects 1/k2, increases with increasing cone angle of the tertiary phosphine but the strongly basic phosphine, PCy3, although unreactive towards [(η5-C5H5)(CO)3MoR] and [(η5-C5H5)(CO)2FeR], induces insertion. Steric influences on the cis/trans isomerisation of the acyl product and its decarbonylation are discussed. Direct insertion of CO is observed for 2,4,6-triisopropyl- and 2,4,6-trimethyl-benzylmanganese complexes.

Homogeneous activation of the CH bond in formates. Decarbonylation of formates to alcohols

Triruthenium dodecacarbonyl in the presence of a basic phosphine catalyzes the decarbonylation of formates to the corresponding alcohols in high yield and with high selectivity. The reactions involving methyl and ethyl formate require the basic tricyclohexylphosphine. The reaction path is believed to involve oxidative addition of the CH bond to the ruthenium cluster.

Nucleophilic addition of phosphines to carbonyl groups. Isolation of 1-hydroxy phosphonium and 1-(trimethylsiloxy) phosphonium salts and the crystal structure of (1-hydroxy-1-methylethyl)triethylphosphonium bromide

1-Hydroxy phosphonium salts and 1-(trimethylsiloxy) phosphonium salts can be isolated by nucleophilic addition of a small basic phosphine (PMe 3 or PEt 3 ) to the carbonyl carbon of aldehydes or ketones in the presence of Br 2 -acetone (a source of anhydrous HBr), anhydrous acids, or chlorotrimethylsilane as trapping agents. The crystal structure of [(CH 3 ) 2 C(OH)(PEt 3 )]Br, Ib, was determined through X-ray diffraction

Ligand-substitution reactions of cationic .sigma.-vinylplatinum(II) triflate species. Single-crystal molecular structure of trans-(CH3)2C:CHPt(PPh3)2I

A wide variety of nucleophiles readily react with the cationic (σ-R 2 C=CR')(Ph 3 P) 3 PtOTf complex, under mild conditions, resulting in ligand substitution. Neutral nucleophiles such as pyridine, CH 3 CN, and CO give the corresponding trans cationic complexes via net replacement of the trans-Ph 3 P ligand. Reactions with an excess of more basic phosphines such as Ph 2 MeP and triphos yield the respective cationic complexes with replacement of all three Ph 3 P ligands. Interaction with charged nucleophiles such as I − , Br − , Cl − and PhS − results in the neutral trans complexes (σ-R 2 C=CR)(Ph 3 P) 2 PtX

Cationic η3‐allylmetal complexes, 12. Oligomerization of styrene with cationic allylnickel compounds: Catalysts, products and the influence of phosphines

AbstractThe complex [η3‐methylallyl(η4‐cycloocta‐1,5‐diene)nickel] hexafluorophosphate (2) was found to be an efficient catalyst for the oligomerization of styrene without using a Lewis acid. Oligomers and polymers with low degree of polymerization were obtained and characterized by GPC and NMR spectroscopy. Solvents and ligands have a strong effect on the catalyst activity, the molecular weight distributions and the polymer microstructure. The end groups were characterized in the case of the ligand‐free and the tributylphosphine and tricyclohexylphosphine‐modified systems. A terminal benzylidene group was observed except for the latter basic and bulky phosphine which led to a methylene terminal group. A mechanism involving a hydridonickel species is proposed.

Solid-state phosphorus-31 NMR, far-IR, and structural studies on two-coordinate (tris(2,4,6-trimethoxyphenyl)phosphine)copper(I) chloride and bromide

The reactions of acetonitrile solutions of copper(I) chloride, CuCl, and copper(I) bromide, CuBr, with the sterically hindered, highly basic tertiary phosphine ligand tris(2,4,6-trimethoxyphenyl)phosphine ({equivalent to}P(2,4,6){sub 3}) have been shown to form 1:1 monomeric adducts, (P(2,4,5){sub 3}CuX). The two compounds are isomorphous, crystallizing in the tetragonal space group P4{sub 3}. For the chloride, a = 15.237 (4) {angstrom}, c = 12.373 (3) {angstrom}, Z = 4, and R = 0.029 for 2339 observed (I {ge} 3{sigma}(I)) reflections, while for the bromide, a = 15.312 (8) {angstrom}, c = 12.457 (6) {angstrom}, Z = 4, and R = 0.052 for 2148 observed reflections. Cu-P is 2.177 (1) {angstrom} and Cu-Cl is 2.118 (2) {angstrom} in the chloro compound; for the bromide, Cu-P is 2.197 (3) {angstrom} and Cu-Br is 2.259 (2) {angstrom}. In both complexes, the copper atom is displaced toward the nearest o-methoxy oxygen with Cu{hor ellipsis}O = 2.629 (4) (Cl) and 2.628 (7) {angstrom} (Br); P-Cu-X angles are 172.97 (6) (Cl) and 172.00 (9){degree} (Br). Far-infrared spectra show expected strong {nu}(Cu-Cl) and {nu}(Cu-Br) bands at 355 and 262 cm{sup {minus}1}, respectively. Strong bands in the range 90-100 cm{sup {minus}1} are assigned to {delta}(P-Cu-X) bending modes. No bands assignable to {nu}(Cu-P)more » modes were observable. The solid-state {sup 31}P NMR spectrum of the ligand is characterized by a single line at -73 ppm (with respect to 85% H{sub 3}PO{sub 4}). The spectrum for each complex shows an asymmetric quartet centered at -65 ppm with highly asymmetric line spacings of 1.40, 2.21, and 2.50 kHz and 1.48, 2.17, and 2.43 kHz, respectively. These data have been used to estimate copper nuclear quadrupole coupling constants for the two compounds. 20 refs., 5 figs., 4 tabs.« less

Rhodium complexes possessing the unidentate anion of 2,4-pentanedione as a ligand; X-ray crystal structure of carbonyl(2,4-pentanedionato-O)bis(tri-isopropylphosphine)rhodium(I)

Rhodium complexes having the unidentate anion of 2,4-pentanedione as a ligand have been synthesized by the reaction of [Rh(acac)(CO)2][Hacac = acetylacetone (2,4-pentanedione)] with highly basic tertiary phosphines. The X-ray crystallographic analysis revealed that the co-ordination chemistry about the Rh atom is square planar with two phosphine ligands in trans positions. The unidentate 2,4-pentanedionate ligand has a trans configuration with respect to the CC bond. Proton n.m.r. studies indicated a singlet resonance for the methine of the pentanedione anion, which is widely accepted as a proof of the cis configuration. In the i.r. spectra absorptions characteristic of the unidentate pentanedionate were observed in the 1 500–1 620 cm–1 region, but the ketonic absorptions were unusually low for αβ-unsaturated carbonyls.

Dimerization of ethylene into 1-butene over supported tailor-made nickel catalysts

Four, two, or one L = PEt 3 ligands are selectively introduced into the coordination sphere of silica-supported Ni(I) ions. Reflectance and EPR spectra are given. The five-coordinate species Ni IL 4(O s) are inactive in C 2H 4 dimerization. The square planar Ni IL 2(O 5) 2 and the unsaturated Ni IL(O s) 2 species are active, stable and selective at 40 °C. The best results are observed with two PEt 3 ligands: at a conversion of 23%, a selectivity of 95% for 1-butene is obtained. The turnover rates ( v) are about 0.1 s −1. From EPR studies a reaction mechanism is proposed. An intermediate metallacyclopentane is characterized. It is shown that the presence of basic phosphine ligands increases the electron density on nickel and allows an easier desorption of the primary reaction products.

ChemInform Abstract: Highly Nucleophilic Triphenylphosphines

General properties of highly basic and nucleophilic tertiary phosphines, tris (2, 6-dimethoxyphenyl) phosphine and tris (2, 4, 6-trimethoxyphenyl) phosphine, are discribed.

Activation of dichloromethane by basic rhodium(I) and iridium(I) phosphine complexes. Synthesis and structures of fac-[Rh(PMe3)3Cl2(CH2PMe3)]Cl·CH2Cl2and trans-[Rh(Me2PCH2CH2PMe2)2Cl(CH2Cl)]Cl

Sixteen-electron RhI complexes of basic phosphines react with CH2Cl2 yielding either RhCH2Cl or RhCH2PMe3 complexes; an example of each has been structurally characterized.