The reactions of the anions [Cp-2(CO)(4)Mo-2(mu-PRR ')](-) (R, R ' = H, Ph) towards chloroarsines and chlorophosphines; synthesis of complexes containing both bridging phosphido and arsenido groups

Deprotonation of the complexes [Cp-2(CO)(4)Mo-2(mu-(PRR2)-R-1)(mu-H)] (R-1 and R-2=H or Ph; Cp=cyclopentadienyl) in THF yields the related anions [Cp- 2(CO)(4)Mo-2(mu-(PRR2)-R-1)](-). The reactivity of these anions towards Ph2 PCl, (EtO)(2)PCl, Ph2AsCl and Me2AsCl has been investigated. The outcome of the reactions with chlorophosphines depends on the nature of the substitue nts on the bridging phosphido ligand. Thus reaction of [Cp-2(CO)(4)Mo-2(mu- PH2)](-) with Ph2PCl yields [Cp-2(CO)(4)Mo-2{mu-P(H)PPh2}(mu-H)], whereas t he analogous reaction with [Cp-2(CO)(4)Mo-2(mu-PPhR)](-) yields [Cp-2(CO)(x )Mo-2(mu-PPh2)(mu-PPhR)] (R=H, x=4; R=Ph, x=2). Thermolysis of [Cp-2(CO)(4) Mo-2(mu-PPhH)(mu-PPh2)] in toluene yields [Cp-2(CO)(2)Mo-2(mu-PPhH)(mu-PPh2 )] and [Cp-2(CO)(O)Mo-2(mu-PPhH)(mu-PPh2)]. In contrast, the reaction of [C p-2(CO)(4)Mo-2(mu-(PRR2)-R-1)](-) with chloroarsines is not dependent on th e nature of the R groups either on the phosphorus or arsenic atoms, yieldin g [Cp-2(CO)(4)Mo-2(mu-(PRR2)-R-1)(mu-AsR23)] in all cases. These complexes are the first example of transition metal compounds containing both a bridg ing phosphido and a bridging arsenido group. The crystal structures of [Cp- 2(CO)(4)Mo-2{mu-P(H)PPh2}(mu-H)], [Cp-2(CO)(4)Mo-2(mu-PPhH){mu-P(OEt)(2)}], and [Cp-2(CO)(4))Mo-2(mu-PH2)(mu-AsMe2)] are reported.