New dinuclear diphenylphosphido-bridged palladium(I) derivatives and the X-ray crystal and molecular structures of the mononuclear homoleptic diphenylphosphine complexes Pd(PPh2H)4 and [Pd(PPh2H)4](BF4)2

By reacting CpPd(η3-C3H5) with PPh2H we isolated the doubly bridged dinuclear complex [Pd2(μ-PPh2)2(PPh2H)3] (1). This reacts with HBF4 yielding the mono-phosphido-bridged cationic derivative [Pd2(μ-PPh2)(PPh2H)4]BF4 (2)BF4, arising from the protonation of one of the bridging phosphides. Contrary to our previous data on the parent t-butyl systems, a mononuclear homoleptic phosphine complex is not an intermediate in the formation of 1. Pd(PPh2H)4 (3), was in fact prepared by an independent route and was shown to decompose thermally to another (uncharacterized) polynuclear derivative; fluoboric acid reacts with 3 yielding its palladium(II) analogue [Pd(PPh2H)4](BF4)2 (3)(BF4)2, with dihydrogen evolution. We also report the crystal and molecular structures of 3 and (3)(BF4)2, the first homoleptic transition metal complexes of diphenylphosphine to be structurally characterized.