Preparation and properties of cis-[W(N2)2(Ph2PCH2PPh2)2] and trans-[M(N2)2(Ph2PCHCHPPh2)2](M = Mo or W), and the crystal structure of cis-[W(N2)2(PMe2Ph)4]

Abstract

The complexes cis-[W(N₂)₂(Ph₂PCH₂PPh₂)₂](A) and trans-[W(N₂)₂(Ph₂PCHCHPPh₂)₂](B) have been prepared by reduction of WCl₆ or [WCl₄(Ph₂PCHCHPPh₂)] with Mg in tetrahydrofuran (thf) under N₂ in the presence of the appropriate phosphine. Dinitrogen is displaced from (A) by CO to give cis-[W(CO)₂(Ph₂PCH₂PPh₂)₂]. Compound (B) reacts with I₂, FeCl₃, and CuCl₂ to give [W(N₂)₂(Ph₂PCHCHPPh₂)₂]Y (Y = I₃, FeCl₄, or CuCl₂) and with HCl to give the cation [WCl(NNH₂)(Ph₂PCHCHPPh₂)₂]⁺. Both complexes (A) and (B) undergo reversible one-electron oxidation in thf. The complex trans-[Mo(N₂)₂(Ph₂PCHCHPPh₂)₂] gives tans-[Mo(N₂)(RCN)(Ph₂PCHCHPPh₂)₂](R = Me or Et) on treatment with RCN. X-Ray analysis of the related complex, cis-[W(N₂)₂(PMe₂Ph)₄], shows a well defined octahedral structure in which the dinitrogen ligands have different environments and the W–N distances are 1.983 and 2.015(3)Å.