Binuclear Macrocyclic Silver(I) Complex of a Bis(carbone) Pincer Ligand: Synthesis and Application as a Carbone-Transfer Agent

A facile synthesis of a binuclear Ag^I complex 2 of a bis(carbone) ligand L and its application as a carbone-transfer agent for the generation of other transition-metal complexes of Au^I (3), Ni^II (4), and Pd^II (5) is presented. Complex 2 was synthesized through multiple synthetic routes under mild reaction conditions using the tetracationic [LH₄][OTf·Cl]₂ precursor salt, the dicationic [LH₂][OTf]₂ ylide salt, and the free ligand L. The first two synthesis routes require no prior isolation of the air-, moisture-, and temperature-sensitive free ligand L, thus affording complex 2 with high yield and purity. Multinuclear NMR techniques, high-resolution mass spectrometry, and single-crystal X-ray diffraction analysis confirmed the identity of complex 2 as a binuclear Ag^I complex of L with a molecular formula of [L₂Ag₂][OTf]₂ and a 16-membered-ring metallomacrocyclic structure. During the transmetalation reaction with Au^I, the binuclear nature of complex 2 remains intact to give analogous complex 3 ([L₂Au₂][OTf]₂). However, the dimeric structure was disrupted upon the carbone-transfer reaction with Ni^II and Pd^II, yielding mononuclear C-N-C pincer-type complexes 4 ([LNiCl][OTf]) and 5 ([LPdCl][OTf]), respectively. These results demonstrated the versatile use of complex 2 as a carbone-transfer agent to other transition metals regardless of the type or size of the metals or the geometry they prefer.