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Tris(o-mercaptophenyl) phosphinate (PS3) binds to Tc(III) as a tetradentate ligand to form the formally 14-electron complex Tc(PS3)(CNMe). An x-ray single-crystal structure determination of the isopropyl isocyanide derivative Tc(PS3)(CN-i-Pr) shows sulfurs bound in the equatorial plane. The crystal data for MF = C{sub 22}H{sub 19}NPS{sub 3}Tc is presented. In the presence of a large excess of isonitrile, these electron-deficient complexes bind a sixth ligand. The six-coordinate complex Tc(PS3)(CN-i-Pr){sub 2}, was also structurally characterized and the crystal data is presented. 8 refs., 2 figs., 4 tabs.

A methanol solution of the Tc(VI) complex (Ph 4 As)[TcNCl 4 ] is reduced in the presence of pyridine to give the orange Tc(V) complex [TcN(OH)(py) 4 ](Ph 4 B) (1); the pyridine ligands are labile and undergo exchange with free pyridine in solution. The TcO 2 + and TcN(OH) + cores also appear to be similar electronically, since the 99 Tc NMR chemical shifts for these two compounds are not significantly different. Compound 1 reacts with 2,3,5,6-tetramethylbenzenethiolate (tmbt) to give quantitative yields of the robust compound trans-TcN(tmbt) 2 (py) 2

Both Tc(III) compounds Tc(tmbt){sub 3}(MeCN){sub 2} (6) and Tc(tmbt){sub 3}(py){sub 2} (7) an be oxidized to Tc(V) oxo species by oxygen atom transfer. The initial product of the reaction of 6 with DMSO was characterized by x-ray crystallography and found to be Tc(tmbt){sub 3}(DMSO)(MeCN), the product of ligand substitution, not oxygen atom transfer. However, compound 6 is oxidized to TcO(tmbt){sub 3}(py) (1) by pyridine N-oxide, and 7 reacts with a number of other oxygen atom transfer reagents as well to produce the oxotechnetium(V) complex 1. The Tc(V) oxo compound TcO(SC{sub 15}H{sub 23}){sub 3}(NC{sub 5}H{sub 5}) (1) was also characterized by x-ray cyrstallography. Addition of excess thiolate to 1 yields (Ph{sub 4}As) (TcO(tmbt){sub 4}) (3), which can also be prepared directly from (Ph{sub 4}As)(TcOCl{sub 4}). Both 1 and 3 can be reduced by oxygen atom abstraction to restore the Tc(III) tris(thiolate) core. Reaction of 3 with PEt{sub 3} requires much more vigorous conditions than 1 does, but both materials are reduced to Tc(tmbt){sub 3}(PEt{sub 3}){sub 2}. The oxidative and reductive oxo-transfer reactions can be coupled to complete a catalytic cycle. In the oxidation of PPh{sub 3} by DMSO, the catalyst is still fully active after 500 turnovers. 31 refs., 5 figs.,more » 6 tabs.« less

Preparation et structure cristalline de complexes Tc(SC 10 H 13 ) 3 (CH 3 CN) 2 , Tc(SC 10 H 13 ) 3 (CO)(CH 3 CN) et Tc(SC 10 H 13 ) 3 (CO)(C 5 H 5 N)