Base-assisted synthesis of 4-pyridinate gold(i) metallaligands: a study of their use in self-assembly reactions

Abstract

The synthesis of di- and tritopic gold(I) metallaligands of the type [(Au4-py)₂(μ₂-diphosphane)] (diphosphane = bis(diphenylphosphanyl)isopropane or dppip (1), 1,2-bis(diphenylphosphanyl)ethane or dppe (2), 1,3-bis(diphenylphosphanyl)propane or dppp (3) and 1,4-bis(diphenylphosphanyl)butane or dppb (4)) and [(Au4-py)₃(μ₃-triphosphane)] (triphosphane = 1,1,1-tris(diphenylphosphanylmethyl)ethane or triphos (5) and 1,3,5-tris(diphenylphosphanyl)benzene or triphosph (6)) from [(AuCl)₂(μ₂-diphosphane)] or [(AuCl)₃(μ₃-triphosphane)] and 4-pyridylboronic acid in the presence of Cs₂CO₃ has been conducted. Interestingly, when [(AuCl)₂(μ₂-dppm)] (dppm = bis(diphenylphosphanyl)methane) was used as a starting material, the cyclic tetranuclear gold(I) compound [(Au4-py)₂(CH)₂{μ₂-Au(PPh₂)₂}₂] (I) was obtained instead. All the products have been characterized by IR and multinuclear NMR spectroscopy, mass spectrometry and elemental analysis and in the case of 1, 3, 5 and I by X-ray crystallography, which showed the presence of aurophilic interactions in all of them. The obtained metallaligands have been used as building blocks in self-assembly reactions with cis-blocked palladium or platinum acceptor moieties producing [2 + 2] metallamacrocycles or trigonal bipyramidal (TBP) [2 + 3] metallacages in good yields. The photophysical properties of both the metallaligands and the corresponding assemblies have been investigated.