Syntesis, Structures and Luminescence Behavior of Mixed Metal Alkynyl platinum-cadmiun Complexes

Resumen

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 Q 2[cis-Pt(C6F5)2(C≡CR) 2] (1a-1c) with CdCl2·2,5 H2O (1:1) produces dinuclear Pt-Cd adducts Q2-[{cis-Pt(C6F 5)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 (NBu 4)2[cis-Pt(C6F5) 2(C≡CR)2] with Cd(NO3) 2·4H2O produces trinuclear Pt2Cd dianionic complexes (NBu4)2[{cis-Pt(C6F 5)2(μ-κCα:η2- C≡CR)2}2Cd] (3a-3c). The analogous (PMePh 3)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(C6F 5)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) →*(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. © 2006 American Chemical Society.