MODULATION OF TC-NX (X = O OR S) BONDS BY PI-ACCEPTOR LIGANDS

Transfer of a sulfur atom from S2Cl2 to cis- [TcN(Cl) (phen)2] PF6 (phen = 1,10-phenanthroline) yields cis-[Tc(NS)CI(phen)2]PF6, which crystallizes in the triclinic space group, P1BAR (no. 2), with cell parameters a = 9.850(3), b = 16.293(3), c = 8.349(2) angstrom, alpha = 100.06(2), beta = 93.84(3) and gamma = 106.96(3)-degrees. The Tc-NS bond length is 1.782(6) angstrom and the N = S distance is 1.538(6) angstrom with a Tc-N-S bond angle of 170.0(4)-degrees. Reaction of (NH4)2 TcCl6 or NH4TcO4 with hydroxylamine hydrochloride in the presence of 1,10-phenanthroline yields cis-[Tc(NO)(NH3)(phen)2]2+. The compound cis-[Tc(NO)-(NH3) (phen)2] [PF6]2.Me2CO crystallizes in the triclinic space group, P1BAR (no. 2), with a = 11.12(1), b = 14.25(6), c = 10.79(2) angstrom, alpha = 90.4(2), beta = 1079(1) and gamma = 86.0(2)-degrees. The Tc-NO bond length is 1.739(9) angstrom and the N = O distance is 1160(9) angstrom with a Tc-N-O bond angle of 171.9(8)-degrees. Bond length and electrochemical data between series of complexes containing the [Tc-NX]2+ (X = O or S) core indicate the effect of other pi-acceptor ligands to be greater on thionitrosyl co-ordination.