Synthesis, structures and optical spectroscopy of photoluminescent platinum-linked poly(silylacetylenes)

Abstract

Synthetic routes to a series of novel oligomeric and polymeric platinum(II)-containing silylacetylenes have been developed. The CuI-catalyzed reaction of trans-[Pt(PEt₃)₂PhCl] with the alkynylsilane Ph₂Si(CCH)₂, in a basic medium, afforded the mononuclear trans-[Ph(Et₃P)₂PtCCSiPh₂CCH] (1) and the dinuclear trans-[Ph(Et₃P)₂PtCCSiPh₂CCPt(PEt₃)₂Ph] (2). Complex 1 can be utilized as a key starting material for access to the triplatinum(II) system trans-[Ph(Et₃P)₂PtCCSiPh₂CCPt(PBu₃)₂CCSiPh₂CCPt(PEt₃)₂Ph] (3). Attempted oxidative coupling of 1 only led to the isolation of the triacetylenic species trans-[Ph(Et₃P)₂PtCCCCCCPt(PEt₃)₂Ph] (5), involving cleavage of Si–C(alkyne) bonds. Soluble and thermally stable platinum(II) poly-yne silane polymer trans-[–Pt(PBu₃)₂CCSiPh₂CC–]_n (4) was prepared in good yield by CuI-catalyzed polymerization of trans-[Pt(PBu₃)₂Cl₂] and Ph₂Si(CCH)₂. The single-crystal X-ray structural analyses and DFT calculations were performed on 1, 2 and 5. We report the optical absorption and photoluminescence spectra of these new metal-based oligomeric and polymeric silylacetylenes and the results are compared with platinum(II) poly-ynes with purely acetylenic and (hetero)aromatic conjugated units.