SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF POLYNUCLEAR COMPLEXES CONTAINING THE 8-ELECTRON DONOR BIS(DIPHENYLPHOSPHINO)METHANEDIIDE LIGAND

The compound [AuR2{(Ph2P)2CH}] (R = C6F5) reacts with various gold(i) or silver(I) compounds possessing a labile ligand such as tetrahydrothiophene or perchlorate to give [AuR2{(PhP)2CH-(ML)}]ClO4 (ML = AuPPh3, AuCH2PPh3 or AgPPh3). Treatment of these derivatives with [Au(acac)(PPh3)] or [N(PPh3)2][Au(acac)Cl] (acac = acetylacetonate) leads to [AuR2{(Ph2P)2C-(AuPPh3)(ML)}]ClO4 or [AuR2{(Ph2P)2C(AuPPh3)(AuCl)}], in which the doubly deprotonated bis-(diphenylphosphino)methanediide ligand is an eight-electron donor. The compound [AuR2{(Ph2P)2C-(AuPPh3)2}]ClO4 can also be obtained by reaction of [AuR2{(Ph2P)2CH2}]ClO4 and [Au(acac)(PPh3)] in 1:2 molar ratio. The reaction of [AuR2{(PhP)2CH(AuR)}] with [Au(acac)(PPh3)] or [N(PPh3)2] [Au(acac)Cl] gives the trinuclear complexes [AuR2{(Ph2P)2C(AuR)(AuPPh3)}] or [N(PPh3)2][AuR2{(Ph2P)2C(AuR)(AuCl)}], whereas it reacts with [N(PPh3)2] [Au (acac)2] (molar ratio 2:1) affording the pentanuclear complex [N(PPh3)2][{AuR2[(Ph2P)2C(AuR)]}2Au]. Another pentanuclear derivative [{AuR2[(Ph2P)2C(AuPPh3)]}2Au]ClO4 is obtained by treatment of [{AuR2[(Ph2P)2CH]}2Au]ClO4 with 2 equivalents of [Au(acac)(PPh3)]. The compounds were characterized by elemental analysis, IR and NMR spectroscopy, and some by fast atom bombardment mass spectrometry. The crystal structure of [AuR2{(Ph2P)2C(AuPPh3)2}]ClO4.CH2Cl2 was confirmed by X-ray diffraction analysis. The complex contains a triangular Au2C unit with a short Au ... Au contact of 2.826(2) angstrom and a narrow Au(1)-C(1)-Au(2) angle of 85.4(7)-degrees.