Synthesis of Co2Pt, Co2Pd and MoPd2 mixed-metal clusters with the P-N-P assembling ligands (Ph2P)2NH (dppa) and (Ph2P)2NMe (dppaMe).: Crystal structure of [Co2Pt(μ3-CO)(CO)6(μ-dppa)]

Heterometallic triangular platinum-cobalt, palladium-cobalt and palladium-molybdenum clusters stabilized by one or two bridging diphosphine ligands such as Ph2PNHPPh2 (dppa) or (Ph2P)(2)NMe (dppaMe) or by mixed ligand sets Ph2PCH2PPh2 (dppm)/dppa have been prepared with the objectives of comparing the stability and properties of the clusters as a function of the short-bite diphosphine ligand used and of the metal carbonyl fragment they contain. Ligand redistribution reactions were observed during the purification of [Co2Pd(mu(3)-CO)(CO)(4)(mu-dppa)(mu-dppm)] (4) by column chromatography with the formation of [Co2Pd(mu(3)-CO)(CO)(4)(mu-dppm)(2)] and the dinuclear complex [(OC)(2)Co(mu-dppa)2PdCl] (5). The latter was independently prepared by reaction of [Pd(dppa-P,P')(2)](BF4)(2) with Na[Co(CO)(4)]. Attempts to directly incorporate the ligand (Ph2P)(2)N(CH2)(3)Si(OMe)(3) (dppaSi) into a cluster or to generate it by N-functionalization of coordinated dppa were unsuccessful, in contrast to results obtained recently with related clusters. The crystal structure of [Co2Pt(mu(3)-CO)(CO)(6)(mu-dppa)] (1) has been determined by X-ray diffraction. (C) 1999 Elsevier Science S.A. All rights reserved.