Diphosphine bifunctional chelators for low-valent metal ions. Crystal structures of the copper(I) complexes [CuClL12] and [CuL12][PF6] [L1 = 2,3-bis(diphenylphosphino)maleic anhydride

Abstract

The chelating diphosphine 2,3-bis(diphenylphosphino)maleic anhydride (L 1 ) reacted with CuCl to give [CuClL 1 2 ] 1a in which the copper is bound to three phosphorus atoms and one chlorine in a pseudo-tetrahedral structure, as demonstrated by X-ray crystallography. Compound L 1 reacted with [Cu(MeCN) 4 ][PF 6 ] to give the red salt [CuL 1 2 ][PF 6 ] 1b in which the copper is bound by four phosphorus atoms of two chelating bidentate ligands, as demonstrated by X-ray crystallography. Addition of chloride ions to 1b quantitatively affords 1a. Complex 1a can be converted quantitatively into [CuL 1 2 ][NO 3 ] 1c by treatment with AgNO 3 . These complexes reacted quantitatively with water, benzylamine and methanol to give the corresponding [CuL 2 2 ] + 2, [CuL 3 2 ] + 3 and [CuL 4 2 ] + 4 where L 2 = 2,3-bis(diphenylphosphino)maleic acid and L 3 and L 4 are the monobenzylamide and monomethyl ester derivatives, respectively, of L 2 . Uncomplexed L 1 can also be hydrolysed to L 2 or derivatised with benzylamine or methanol to give L 3 and L 4 respectively. Compounds L 2 , L 3 and L 4 reacted with copper-(I) or -(II) salts to yield salts of 2, 3 and 4. This chemistry provides versatile routes to the synthesis of stable bioconjugates containing copper or radiocopper and of derivatised solids containing pendant diphosphine ligands.