Modulation of Tc–NX (X = O or S) bonds by π-acceptor ligands

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Abstract
Transfer of a sulfur atom from S2Cl2 to cis-[TcN(Cl)(phen)2]PF6(phen = 1,10-phenanthroline) yields cis-[Tc(NS)Cl(phen)2]PF6, which crystallizes in the triclinic space group, P(no. 2), with cell parameters a= 9.850(3), b= 16.293(3), c= 8.349(2)Å, α= 100.06(2), β= 93.84(3) and γ= 106.96(3)°. The Tc–NS bond length is 1.782(6)Å and the NS distance is 1.538(6)Å with a Tc–N–S bond angle of 170.0(4)°. Reaction of (NH4)2TcCl6 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, P(no. 2), with a= 11.12(1), b= 14.25(6), c= 10.79(2)Å, α= 90.4(2), β= 107.9(1) and γ= 86.0(2)°. The Tc–NO bond length is 1.739(9)Å and the NO distance is 1.160(9)Å with a Tc–N–O bond angle of 171.9(8)°. Bond length and electrochemical data between series of complexes containing the [Tc–NX]2+(X = O or S) core indicate the effect of other π-acceptor ligands to be greater on thionitrosyl co-ordination.