Gary R. Cooper

Syntheses and michael additions to vinylidene diphosphine complexes of type [M(CO)4{(Ph2P)2CCH2}] (MCr, Mo or W)

Treatment of [M(CO)4Ph2PCHPPh2]− with CH3- OCH2Cl at 20 °C gave the methoxymethyl derivations [M(CO)4{Ph2PCH(CH2OCH3)PPh2}] (MCr or W), but a similar treatment at 80 °C gave derivatives of a vinylidene diphosphine [M(CO)4(Ph2P)2C CH2]. Treatment of [M(CO)4Ph2PCHPPh2]−with CH3CHClOCH3 at 20 or 80 °C gave only [M(CO)4- (Ph2P)2CHCH(CH3)OCH3] (MCr or W). The vinylidene diphosphine complexes [M(CO)4(Ph2P)2- CCH2] (MCr, Mo or W) were even more easily prepared by treating [M(CO)6] with (Ph2P)2CCH2 (vdpp) in hot solvents such as CH3OCH2CH2OCH2- CH2OCH3. Treatment of [W(CO)4vdpp] with LiBun followed by methanol gave [W(CO)4(Ph2P)2CHCH2Bun] (1c), i.e. conjugate addition to the CCH2 occurs. 1c was also made by treating [W(CO)4(Ph2P)2CH]− with n-pentyl-iodide. Similarly LiMe was added to [W(CO)4(Ph2P)2CCH2]. Treatment of [M(CO)4- vdpp] with NaCH(COOEt)2 gave [M(CO)4(Ph2- P)2CHCH2CH(COOEt)2] (MW or Mo). Pyrrolidine added to the CCH2 bonds of [M(CO)4vddp] to give [M(CO)4(Ph2P)2CHCH2NC4H8]. 31p and 1H NMR and IR data are given.

Bimetallic systems. Part 4. Synthesis and characterisation of mixed copper(I)–, silver(I)–, or gold(I)–platinum(II) acetylide complexes containing bridging Ph2PCH2PPh2

The bis(monodentate dppm)diacetylide complexes of type trans-[Pt(CCR)2(dppm-P)2](dppm = Ph2PCH2PPh2; R = Ph, p-tolyl, Me, etc.) react with silver nitrate or silver hexafluorophosphate to give mixed platinum–silver salts of the type [(RCC)2Pt(µ-dppm)2Ag]X (X = NO3– or PF6–) or with [{AgX(PPh3)}4](X = Cl or I) to give neutral platinum–silver complexes, [(RCC)2Pt(µ-dppm)2-AgX](X = Cl or I), in excellent yield. The salts and neutral complexes can be interconverted, e.g. the nitrate salt with NaI gives the neutral platinum–silver iodide complex and when the neutral platinum–silver chloride complex [(PhCC)2Pt(µ-dppm)2AgCl] is treated with [NH4][PF6] in acetone the corresponding [PF6]– salt is formed. A more convenient method of synthesis of the complex [(PhCC)2Pt(µ-dppm)2AgX] is to treat [Pt(dppm-PP′)2]X2(X = Cl or I) with two equivalents of AgO2CMe + PhCCH. Treatment of [Pt(dppm-PP′)2]X2 with one equivalent of AgO2CMe + RCCH gives platinum–silver monoacetylides of type [(RCC)ClPt(µ-dppm)2AgCl](R = Ph, p-tolyl, Me, CH2CH2Ph, or CMeCH2). In ‘one-pot’ reactions PtCl2(or K2[PtCl4]) was treated with two equivalents of dppm followed by one equivalent of AgO2CMe + PhCCH to give the complex [(PhCC)ClPt(µ-dppm)2AgCl] in 71% overall yield. This chloro-complex, when treated with LiBr or NaI in dichloromethane–acetone, gave the corresponding bromo- or iodo-complexes [(PhCC)XPt-(µ-dppm)2AgX](X = Br or I) in ca. 90% yields. Treatment of [Pt(CCC6H4Me-P)2(dppm-p)2] with [AuCl(PPh3)] gave the platinum–gold complex salt [(p-MeC6H4CC)2Pt(µ-dppm)2Au]Cl. Treatment of [Pt(dppm-PP′)2]Cl2 with Li[Cu(CCPh)2] gives [(PhCC)2Pt(µ-dppm)2CuCl], which in acetone solution + Na[BPh4] gives the corresponding salt [(PhCC)2Pt(µ-dppm)2Cu][BPh4]. All of the complexes were characterised by microanalysis, solution conductivity measurements, i.r. spectroscopy, and particularly 31P-{1H} and 1H-{31P} n.m.r. spectroscopy. The variable-temperature 1H-{31P} and 31P-{1H} n.m.r. spectra of the complexes are discussed.

A mechanistic study on complexes of type mer-[Cr(CO)3(η2-L–L)(σ-L–L)](where L–L = Ph2PCH2PPh2, Ph2PNHPPh2, or Ph2PNMePPh2) using spectroscopic and convolutive electrochemical techniques

The new complexes mer-[Cr(CO)3(η2-L–L)(σ-L–L)][where L–L = Ph2PCH2PPh2(dppm), Ph2PNHPPh2(dppa) or Ph2PNMePPh2(dppma)] were synthesized by treating [Cr(CO)3(C7H8)](C7H8= cyclohepta-1,3,5-triene) with the appropriate diphosphine. The complexes were characterized by i.r. and by 31P-{1H} and 1H-{31P} n.m.r. spectroscopy. The electrochemical and chemical oxidation of these complexes was investigated and the products identified by electrochemical techniques and by e.s.r. and i.r. spectroscopy. The one-electron oxidation of mer-[Cr(CO)3(η2-L–L)(σ-L–L)] gives the 17-electron chromium(I) complex mer-[Cr(CO)3(η2-L–L)(σ-L–L)]+. These chromium(I) complexes have only limited stability and have been shown to follow two reaction pathways, disproportionation (electron transfer) as in equation (i) and intramolecular displacement of CO as in equation (ii). The rates of these reactions increase markedly from L–L = dppm to dppa or dppma. A second one-electron oxidation process [equation (iii)] has been observed but the dications are very unstable and decompose to give solvated Cr2+, free diphosphine, and CO gas. 2 mer-[Cr(CO)3(η2-L–L)(σ-L–L)]+→mer-[Cr(CO)3(η2-L–L)(σ-L–L)]0+mer-[Cr(CO)3(η2-L–L)(σ-L–L)]2+(i), mer-[Cr(CO)3(η2-L–L)(σ-L–L)]+→trans-[Cr(CO)2(η2-L–L)2]++ CO (ii), mer-[Cr(CO)3(η2-L–L)(σ-L–L)]+→mer-[Cr(CO)3(η2-L–L)(σ-L–L)]2++ e (iii)

Ring opening reactions of [M(CO)3(η1-Ph2PCH2PPh2)(η2-Ph2PCH2PPh2)] M = Cr, Mo, or W with Rh or Ir complexes to give bimetallic systems: synthesis of [(OC)3Mo(µ-Ph2PNHPPh2)2RhCl(CO)]

Complexes of the type [(OC)3M(µ-Ph2PCH2PPh2)2M′X(CO)] or [(OC)3M(µ-Ph2PCH2PPh2)2M′(CO)2]+PF6– have been made either as described in the title or by a ring opening reaction of [M′(CO)(η2-Ph2PCH2PPh2)2]Cl (M′= Rh or Ir) with a labile Cr, Mo, or W carbonyl derivative: the first bimetallic complex of Ph2PNHPPh2 is described.

Novel routes to functionalized diphosphine-M(CO)4 complexes (M = W, Mo, or Cr)

Complexes of type [(OC)4M{(Ph2P)2CCH2}] undergo Michael type additions with a range of amines, including optically active amines, hydrazines, acetylides, and dichlorocarbene and the products can be used for further syntheses.