Dinuclear PCP pincer complexes from Lewis acidic [Pd(OTf)(PCP)] and basic [Pd(4-Spy)(PCP)] (OTf = triflate; 4-Spy = 4-pyridinethiolate; PCP = −CH(CH2CH2PPh2)2)

Abstract

The Lewis acidic pincer with a labile triflate ligand, viz. [Pd(OTf)(PCP)] (PCP = ⁻CH(CH₂CH₂PPh₂)₂) 1 was prepared from [PdCl(PCP)] with AgOTf. It reacts readily with neutral bidentate ligands [L = 4,4′-bipyridine (4,4′-bpy) and 1,1′-bis(diphenylphosphino)ferrocene (dppf)] to give dinuclear PCP pincers [{Pd(PCP)}₂(μ-L)][OTf]₂ (L = 4,4′-bpy, 2; dppf, 3). [PdCl(PCP)] also reacts with 4-mercaptopyridine in the presence of KOH to give a Lewis basic pincer with a free pyridine functional group [Pd(4-Spy)(PCP)] 4. Its metalloligand character is exemplified by the isolation of an asymmetric dinuclear double-pincer complex [{Pd(PCP)}₂(μ-4-Spy)][PF₆] 6 bridged by an ambidentate pyridinethiolato ligand. Complexes 1, 2, 3, 4 and 6 have been characterized by single-crystal X-ray diffraction analyses.