Nitrosyl and Thionitrosyl Complexes of Technetium and Rhenium and Their Reactions with Hydrotris(pyrazolyl)borates.

The very limited number of structurally known thionitrosyl complexes of technetium was increased by the synthesis of [Tc(NS)Cl(PPh)] () and [Tc(NS)Cl(PPh)(OPPh)] () and their reaction products with hydrotris(pyrazolyl)borates, {HB(pz)}. Similar reactions were conducted with [Tc(NO)Cl(PPh)(CHCN)] and related rhenium thionitrosyls. Remarkably, most such reactions result in a rapid cleavage of the boron-nitrogen bonds of the ligands and the formation of pyrazole complexes of the two group 7 metals. Only one compound with an intact {HB(pz)} ligand could be isolated: the technetium(I) complex [Tc(NO)Cl(PPh){HB(pz)}] (). Other products show the coordination of one or four neutral pyrazole ligand(s) in the coordination spheres of technetium generated by thermal decomposition of the pyrazolylborates [Tc(NO)Cl(PPh)(pz)] () and [Tc(NS)Cl(pz)] (). Reactions with the corresponding thionitrosylrhenium complex [Re(NS)Cl(PPh)] require higher temperatures and only compounds with one pyrazole ligand, [Re(NS)Cl(PPh)(pz)] (-), were isolated. The products were studied spectroscopically and by X-ray diffraction.