Crystal structures of nitridotechnetium(V) complexes of amine oximes differing in carbon chain lengths

Abstract

Structures of nitridotechnetium(V) amine oxime complexes, [TcN(pnao)(H2O)][BPh4] 1, [TcN(bnao)(H2O)][BPh4] 2 and [TcN(pentao)(H2O)][BPh4] 3 [Hpnao = HONCMeCMe2NH(CH2)3NHCMe2CMeNOH; Hbnao = HONCMeCMe2NH(CH2)4NHCMe2CMeNOH; Hpentao = HONCMeCMe2NH(CH2)5NHCMe2CMeNOH], differing in carbon chain length of the amine oxime ligands, were characterized by X-ray crystallography. These complexes are six-co-ordinated and distorted octahedral. Four nitrogen atoms of the amine oxime ligands are in the equatorial plane and both the nitrido and H2O ligands in the apical positions. These complexes have an asymmetrical intramolecular hydrogen bond between the two oxime oxygen atoms. Their intramolecular O· · ·O distances are 2.720 A in 1, 2.512 A in 2 and 2.531 A in 3. The longest O· · ·O distance in 1 is ascribed to a steric effect of the carbon chain length between the amine nitrogens. Namely, the shorter carbon chain of the pnao ligand causes strain on the co-ordinated pnao moiety, and the O· · ·O distance in 1 is longer than that in 2 and 3 with longer carbon chains.