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 η 2 -alkyne−cadmium bonding. Treatment of Q 2 [ cis -Pt(C 6 F 5 ) 2 (C⋮CR) 2 ] ( 1a − 1c ) with CdCl 2 ·2,5 H 2 O (1:1) produces dinuclear Pt−Cd adducts Q 2 [{ cis -Pt(C 6 F 5 ) 2 (μ-κ C α:η 2 -C⋮CR) 2 }(CdCl 2 )] (Q = NBu 4, R = t- Bu 2a; Q = PMePh 3, R = Ph 2b; R = Tol 2c ). However, reaction of (NBu 4 ) 2 [ cis -Pt(C 6 F 5 ) 2 (C⋮CR) 2 ] with Cd(NO 3 ) 2 ·4H 2 O produces trinuclear Pt 2 Cd dianionic complexes (NBu 4 ) 2 [{ cis -Pt(C 6 F 5 ) 2 (μ-κ C α:η 2 -C⋮CR) 2 } 2 Cd] ( 3a − 3c ). The analogous (PMePh 3 ) 2 [{ cis -Pt(C 6 F 5 ) 2 (μ-κ C α:η 2 -C⋮CR) 2 } 2 Cd] (R = Ph 3b ‘; Tol 3c ‘) were prepared similarly starting from (PMePh 3 ) 2 [ cis -Pt(C 6 F 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 PtC 4 Cd 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 η 2 -complexation. The arylalkynyl derivatives ( b, c ) display intense structured emission bands, arising from 3 ππ*(C⋮CR) (IL) and/or mixed 3 ππ*/Pt(d π )(C⋮CR) → π*(C⋮CR) ( 3 MLCT) manifolds with a predominant IL character.