Diverse structural reactivity patterns of a POCOP ligand with coinage metals

Abstract

We have utilised the 4,6-di-tert-butyl resorcinol bis(diphenylphosphinite) (POCOP) ligand for exploring its coordination ability towards group 11 metal centres. The treatment of the bidentate ligand 1 with various coinage metal precursors afforded a wide range of structurally diverse complexes 2-12, depending upon the metal precursors used. This furnishes several multinuclear Cu(i) complexes with dimeric (2) and tetrameric cores (3, 4, and 5). The tetrameric stairstep complex 4 shows thermochromic behaviour, whereas the dimeric complex 2 and tetrameric complex 3 show luminescence properties at cryogenic temperatures. Interestingly, the halide substitution reaction of the dimeric complex 2 with KPPh2 produces a unique mixed phosphine-based tetrameric Cu(i) complex, 5. Treatment of the POCOP ligand with [CuBF4(CH3CN)4] in the presence of 2,2 '-bipyridine afforded heteroleptic complex 6, consisting of tri- and tetra-coordinated cationic Cu(i) centres. Furthermore, we could also isolate cubane (8) and stairstep (9) complexes of Ag(i). The cationic Au(i) complex (12) was obtained from the dinuclear Au(i) complex of POCOP, 11. Complex 12 revealed the presence of a strong intramolecular aurophilic interaction with an AuMIDLINE HORIZONTAL ELLIPSISAu bond distance of 3.1143(9) angstrom. Subsequently, the photophysical properties of these complexes have been studied. All the complexes were characterised by single-crystal X-ray diffraction studies, routine NMR techniques, and mass spectroscopy. Herein, we report an interesting coordination pattern of a POCOP-based pincer ligand towards various coinage metals, displaying a variety of distinct structural architectures and photophysical properties.