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 II (NS)Cl 3 (PPh 3 ) 2 ] ( 3 ) and [Tc II (NS)Cl 3 (PPh 3 )(OPPh 3 )] ( 4 ) and their reaction products with hydrotris(pyrazolyl)borates, {HB(pz R ) 3 } - . Similar reactions were conducted with [Tc I (NO)Cl 2 (PPh 3 ) 2 (CH 3 CN)] 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 R ) 3 } - ligand could be isolated: the technetium(I) complex [Tc I (NO)Cl(PPh 3 ){HB(pz) 3 }] ( 2 ). 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 I (NO)Cl 2 (PPh 3 ) 2 (pz H )] ( 1 ) and [Tc I (NS)Cl(pz HMe2 ) 4 ] + ( 5 ). Reactions with the corresponding thionitrosylrhenium complex [Re II (NS)Cl 3 (PPh 3 ) 2 ] require higher temperatures and only compounds with one pyrazole ligand, [Re I (NS)Cl 2 (PPh 3 )(pz HR )] ( 6a - 6c ), were isolated. The products were studied spectroscopically and by X-ray diffraction.