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The very limited number of structurally known thionitrosyl complexes of technetium was increased by the synthesis of TcII (NS) Cl3 (PPh3) 2 (3) and TcII (NS) Cl3 (PPh3) (OPPh3) (4) and their reaction products with hydrotris (pyrazolyl) borates, HB (pzR) 3−. Similar reactions were conducted with TcI (NO) Cl2 (PPh3) 2 (CH3CN) 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 (pzR) 3− ligand could be isolated: the technetium (I) complex TcI (NO) Cl (PPh3) 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 TcI (NO) Cl2 (PPh3) 2 (pzH) (1) and TcI (NS) Cl (pzHMe2) 4+ (5). Reactions with the corresponding thionitrosylrhenium complex ReII (NS) Cl3 (PPh3) 2 require higher temperatures and only compounds with one pyrazole ligand, ReI (NS) Cl2 (PPh3) (pzHR) (6a–6c), were isolated. The products were studied spectroscopically and by X-ray diffraction.
Sawallisch et al. (Thu,) studied this question.