Synthesis, Structures, and Luminescence Behavior of Mixed Metal Alkynyl Platinum−Cadmium Complexes

Abstract

This article describes the preparation, characterization, and optical properties of new bi- and trinuclear tweezer-type platinum cadmium derivatives, stabilized by η2-alkyne−cadmium bonding. Treatment of Q2[cis-Pt(C6F5)2(C⋮CR)2] (1a−1c) with CdCl2·2,5 H2O (1:1) produces dinuclear Pt−Cd adducts Q2[{cis-Pt(C6F5)2(μ-κCα:η2-C⋮CR)2}(CdCl2)] (Q = NBu4, R = t-Bu 2a; Q = PMePh3, R = Ph 2b; R = Tol 2c). However, reaction of (NBu4)2[cis-Pt(C6F5)2(C⋮CR)2] with Cd(NO3)2·4H2O produces trinuclear Pt2Cd dianionic complexes (NBu4)2[{cis-Pt(C6F5)2(μ-κCα:η2-C⋮CR)2}2Cd] (3a−3c). The analogous (PMePh3)2[{cis-Pt(C6F5)2(μ-κCα:η2-C⋮CR)2}2Cd] (R = Ph 3b‘; Tol 3c‘) were prepared similarly starting from (PMePh3)2[cis-Pt(C6F5)2(C⋮CR)2]. The crystal structures of 2c and 3a,b show that the cadmium center is well embedded by the cis-bis(alkyne)platinate entities, leading to planar PtC4Cd cores. In the heterometallic species, the low-energy absorption, which is ascribed to an admixture of π → π*(C⋮CR) IL/dπ(Pt) → π*(C⋮CR) MLCT, exhibits a clear hypsochromic shift compared to its precursors, probably due to the existence of a lesser delocalization on the alkynyl fragments upon the η2-complexation. The arylalkynyl derivatives (b, c) display intense structured emission bands, arising from 3ππ*(C⋮CR) (IL) and/or mixed 3ππ*/Pt(dπ)(C⋮CR) → π*(C⋮CR) (3MLCT) manifolds with a predominant IL character.