Synthesis and reactivity of bis(diphenylphosphine) methane(dppm)-bridged Pd–Mo and Pd–W complexes. Crystal structure of [Pd(µ-CO)(µ-dppm)2Mo(cp)(CO)][PF6](cp =η5-C5H5)

Abstract

Reactions of [PdCl2(dppm-PP′)](dppm = Ph2PCH2PPh2) with Na[M′(CO)]·2dme [M′= Mo(cp)(CO)2 or W(cp)(CO)2; cp =η5-C5H5, dme = 1,2-dimethoxyethane] gave trinuclear clusters of type [PdM2(cp)(CO)5(µ-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 [[graphic omitted](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)A, β= 90.79(2)°, 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)A]. 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 31P-{1H} NMR spectra are respectively of the AA′XX′ and AA′BB′ types. Reactivity studies were performed and the new bimetallic complex [(OC)2(cp)[graphic omitted]tCl(PPh3)]8 is also described.