Self assembly of group 11 complexes with 2-mercaptothiazoline : their syntheses and reactions

Abstract

A series of butterfly-like complexes, containing in their cores either copper or silver atoms, has been prepared by addition of a Lewis base (PPh3, AsPh3, or py, where Ph = C6H5, and py = pyridine) to the insoluble precipitate obtained between the reaction of the corresponding metal acetate with 2-mercaptothiazoline (HMT), in stoichiometric proportion. These compounds are: (PPh3)2Cu4(MT)4, 2, (AsPh3)2Cu4(MT)4, 3, pyCu4(MT)4, 4, (PPh3)2Ag4(MT)4, 6. A mixed copper-silver butterfly complex, (PPh3)2Ag2Cu2(MT)4, 8, was synthesized by addition of PPh3 to the precipitate obtained by the reaction of 2-mercaptothiazoline with a mixture of the metal acetates. The insolubility of the precipitates prevents detailed spectroscopic studies of these complexes. Field Desortion-Mass Spectroscopy (FDMS), however, has provided essential information, showing that the insoluble precipitates are tetranuclear. The addition of pyridine (py) to the insoluble precipitate gives additional information: py adds to only one wing tip copper atom; the other wing tip copper atom interacts with the endocyclic sulfur of the next butterfly unit. The interaction of the endocyclic sulfur atom with the copper atom of the next butterfly unit causes the complexes to be insoluble. All of the complexes with a Lewis base have been structurally characterized. 1H and 31P{H} NMR studies of these complexes suggest fluxional behavior. The reaction of these butterfly-like complexes with some electrophiles (HgCl2) or oxidizing agents (C6H5I*Cl2) yields mononuclear or dinuclear species, that may or may not contain the core metal originally present in the butterfly complex. 2-Mercaptothiazoline is a versatile ligand: it can coordinate through the exocyclic sulfur atom, the endocyclic nitrogen atom, or the endocyclic sulfur atom. This ligand is also known to reduce Cu(II) salts and form Cu(I) complexes. This is demonstrated in the reaction between CuBr2 and HMT, where (HMT)2CuBr, 10, is the product.