The tetraphosphine DPPEPM reacts with [PtMe2(cod)] to produce [PtMe2(DPPEPM-PP)] (1) in near quantitative yield. On standing in solution, the free P atoms become oxidized to give [PtMe2(DPPEPM(O) 2-PP)] (1a), which has been characterized by X-ray crystallography. In contrast, reactions of DPPEPM with [MCl2(cod)] (M = Pd, Pt) yield ionic products of the form [M(DPPEPM-PP)2]MCl4 (3, 4). When a solution of the platinum complex was allowed to stand, crystals of [Pt(μ-Cl)(μ-DPPEPM)2]Cl3 (5) were obtained. In a third set of reactions, treatment of [PtClR(cod)] (R = Me, Ph) or [PdClMe(cod)] with DPPEPM gives species of the type [MR(DPPEPM-PPP)]Cl (6-8), in which one of the internal P atoms is uncoordinated. Reactions of [PtR2(DPPEPM-PP)] with [PtR2′(cod)] or [MCl2(cod)] (M = Pd, Pt), or of [PtR(DPPEPM-PPP)]Cl with [MCl2(cod)], lead to unsymmetrical bimetallic complexes. [PtMe2(μ-DPPEPM)PdCl2] (11) and [PtClPh(μ-DPPEPM)PdCl2] (14) have been characterized crystallographically. Trimetallic complexes of the form [{PtR 2(μ-DPPEPM)}2M][MCl4] (M = Pd, Pt, 15-17) are produced by reaction of [PtR2(DPPEPM-PP)] with [MCl 2(cod)].