Homoleptic versus heteroleptic trinuclear systems with mixed l-cysteinate and d-penicillaminate regulated by a diphosphine linker

Abstract

Controlled generation of homoleptic versus heteroleptic Au^I₂M (M = Ni^II, Zn^II) trinuclear complexes, which is achieved by a slight change in the diphosphine P^P linker of digold(I) metalloligands, [Au₂(P^P)(D-pen)₂]²⁻ (L1^{P^P}; D-pen = D-penicillaminate) and [Au₂(P^P)(L-cys)₂]²⁻ (L2^{P^P}; L-cys = L-cysteinate), is reported. The reactions of a 1 : 1 mixture of L1^dppm and L2^dppm (dppm = bis(diphenylphosphino)methane) with M = Ni^II, Zn^II gave the homoleptic Au^I₂M complexes, [M(L1^dppm)] and [M(L2^dppm)], which co-crystallized to form [M(L1^dppm)]·[M(L2^dppm)] (1_M). Similar reactions using L1^dppe and L2^dppe (dppe = bis(diphenylphosphino)ethane), instead of L1^dppm and L2^dppm, led to the selective production and crystallization of the heteroleptic Au^I₂M complex, [M(L3^dppe)] (2_M; L3^dppe = [Au₂(dppe)(L-cys)(D-pen)]²⁻), accompanied by the scrambling of L1^dppe and L2^dppe. The homoleptic 1_M and the heteroleptic 2_M showed different absorption (green versus blue) and emission (yellow versus orange) colours for M = Ni^II and Zn^II, respectively.