Synthesis, structures, and luminescence behavior of mixed metal alkynyl platinum-cadmium complexes

This article describes the preparation, characterization, and optical properties of new bi- and trinuclear tweezer-type platinum cadmium derivatives, stabilized by eta(2)-alkyne-cadmium bonding. Treatment of Q(2)[cis-Pt(C6F5)(2)(C equivalent to CR)(2)] (1a-1c) with CdCl2 center dot 2,5 H2O (1:1) produces dinuclear Pt-Cd adducts Q(2)-R [{cis-Pt(C6F5)(2)(mu-kappa C-alpha:eta(2)-C equivalent to CR)(2)}(CdCl2)] (Q = NBu4, R = t-Bu 2a; Q = PMePh3, R = Ph 2b; R = Tol 2c). However, reaction of (NBu4)[cis-Pt(C6F5)(2)(C equivalent to CR)(2)] with Cd(NO3)(2)center dot 4H(2)O produces trinuclear Pt2Cd dianionic complexes (NBu4)(2)[{cis-Pt(C6F5)(2)(mu-kappa C-alpha:eta(2)-C equivalent to CR)(2)}(2)Cd] (3a-3c). The analogous (PMePh3)(2)[{cis-Pt(C6F5)(2)(mu-kappa C-alpha:eta(2)-C equivalent to CR)(2)}(2)Cd] (R = Ph 3b'; Tol 3c') were prepared similarly starting from (PMePh3)(2)[{cis-Pt(C6F5)(2)(C equivalent to 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 pi ->pi*(C equivalent to CR) IL/d pi(Pt) -> pi*(C equivalent to CR) MLCT, exhibits a clear hypsochron-tic shift compared to its precursors, probably due to the existence of a lesser delocalization on the alkynyl fragments upon the eta(2)-complexation. The arylalkynyl derivatives (b, c) display intense structured emission bands, arising from (3)pi pi*(C equivalent to CR) (IL) and/or mixed (3)pi pi*/Pt(d(pi))(C equivalent to CR) -> pi*(C equivalent to CR) ((MLCT)-M-3) manifolds with a predominant IL character.