SYNTHESIS AND REACTIVITY OF BIS(DIPHENYLPHOSPHINO)METHANE-(DPPM)-BRIDGED PD-MO AND PD-W COMPLEXES - CRYSTAL-STRUCTURE OF [PD(MU-CO)(MU-DPPM)2MO(CP)(CO)][PF6] (CP = ETA-5-C5H5)

Reactions of [PdCl2(dppm-PP')] (dppm = Ph2PCH2PPh2) with Na[M'(CO)].2dme [M' = Mo(cp)(CO)2 or W(cp)(CO)2; cp = eta-5-C5H5, dme = 1,2-dimethoxyethane] gave trinuclear clusters of type [PdM2-(cp)2(CO)5(mu-dppm)] (M = Mo, 1; or W, 2). Treatment of 1 or 2 with 1 equivalent of dppm resulted in heterolytic metal-metal bond cleavage and afforded dinuclear cationic complexes [activated Pd(mu-CO)(mu-dppm)2M(cp)(CO)][M(cp)(CO)3] (M = Mo, 3a; or W, 4a). The structure of the benzene solvate the PF6- salt of 3, i.e. 3b, was established by a single-crystal X-ray analysis: space group P2/c, a = 23.923(6), b = 11.040(3), c = 24.012(6) angstrom, beta = 90.79(2)-degrees, R = 0.053 for 7361 reflections. The (cp)MoP(1)P(3)(CO)2 fragment is square pyramidal, with the cp at the apex, and the co-ordination at Mo may be viewed as of the 3:4:1 type when including the bonding to Pd [Pd-Mo] 2.799(1) angstrom]. The unusual geometry around Pd is trigonal planar when considering its bonds to P(2), P(4) and Mo. The bridging carbonyl C(56)O(1) completes its co-ordination sphere. Complexes 3b and 4b were also prepared from [Pd(dppm-PP'2)2][BF4]2 and 2 equivalents of Na[M'(CO)].2dme [M' = Mo(cp)(CO)2 or W(cp)(CO)2]. Their characteristic P-31-{H-1} NMR spectra are respectively of the AA'XX' and AA'BB' types. Reactivity studies were performed and the new bimetallic complex [(OC)2(cp) activated Mo(mu-dppm)PtCl(PPh3)] 8 is also described.