TECHNETIUM NITRIDO COMPLEXES WITH AMINE AND THIOLATE LIGANDS - STRUCTURAL CHARACTERIZATION OF TCN(SC6HME4)2(NHC(NME2)2)2, A COMPLEX WITH COORDINATIVELY BOUND 1,1,2,2-TETRAMETHYLGUANIDINE

A methanol solution of the Tc(VI) complex (Ph4As)[TcNCl4] is reduced in the presence of pyridine to give the orange Tc(V) complex [TcN(OH)(py)4](Ph4B) (1). As in the oxo analogue [TcO2(py)4](Ph4B), the pyridine ligands on 1 are labile and undergo exchange with free pyridine in solution. The TcO2+and TcN(OH)+cores also appear to be similar electronically, since the99Tc NMR chemical shifts for these two compounds are not significantly different. Compound 1 reacts with 2,3,5,6-tetramethyl-benzenethiolate (tmbt) to give quantitative yields of the robust compound trans-TcN(tmbt)2(py)2(2). In an attempt to prepare [TcN(tmbt)4]-, [TcNCl4]-was allowed to react with Htmbt in the presence of the “noncoordinating” base 1,1,3,3-tetramethyl-guanidine (TMG). Instead of the desired tetrathiolate complex, TcN(tmbt)2(TMG)2(3), a rare example of TMG coordination, was obtained. This compound shows dimer formation in fast atom bombardment spectra, and the decomposition of this species was studied by tandem mass spectrometry. The structure of 3 was confirmed by a single-crystal X-ray structure determination (crystal data: molecular formula = C30H52N7S3Tc, monoclinic, a = 9.006 (3) Å b = 24.815 (3) Å, c = 15.992 (2) Å, β = 96.57 (2)°, space group = P21/n, Z = 4, final R = 0.048, final Rw = 0.057). © 1990, American Chemical Society. All rights reserved.