Synthesis of Neutral Molecular Squares Composed of Bis(phosphine)platinum Corner Units and Dialkynyl Linkers. Solid-State Characterization of [Pt(μ-C⋮CC⋮C)(dppp)]₄

Abstract

Coupling of dichloroplatinum complexes with ethyne or butadiyne, catalyzed by CuI in the presence of Et2NH, leads to complexes of the types [Pt(C⋮CH)2L2] (L2 = dppe (1), dppp (2); L = PEt3 (3)) and [Pt(C⋮CC⋮CH)2L2] (L2 = dppp (4), dcpe (5); L = PEt3 (6)). Attempts to produce tetraplatinum species with ethynyl edges proved unsuccessful, but further coupling of the butadiynylplatinum complexes with [PtCl2L2] produces the neutral molecular squares [Pt(μ-C⋮CC⋮C)2L2]4 (L2 = dppp (7), dcpe (8); L = PEt3 (9)). This two-step approach allows the synthesis of the unsymmetrical complexes [Pt2(μ-C⋮CC⋮C)2(PEt3)2L2] (L2 = dppp (10); dcpe (11)). The molecular structure of 7 reveals that each square has a puckered, butterfly-like structure. These pack in a face-to-face manner, generating series of channels that accommodate several solvent molecules. Coupling of trans-[Pt(C⋮CC⋮C)2(PEt3)2] (6b) with [PtCl2L2] (L2 = dcpe, dppp) leads to complexes assigned as neutral octaplatinum derivatives. The nitrogen-containing complexes [Pt(C⋮CC5H4N)2(dppp)] (14) and [Pt(C⋮CC6H4CN)2(dppp)] (15) react with AgNO3 to produce Pt4Ag4 adducts.