Reduction of the NO+ ligand in the pentacyanonitrosylosmate(II) ion

The reversible reduction of [Os(CN)(5)(NO)](2-) the osmium analog of the nitroprusside ion, has been studied by sprctroelectrochemical techniques (IR, UV-Vis, EPR). The strong shift of the nitrosyl stretching band from 1850 to 1560 cm(-1) (in acetonitrile) already indicates nitrosyl ligand-centered reduction in comparison to the smaller shifts for the cyanide frequencies (2140 --> 2080 cm(-1)). Remarkably, the g factor analysis (g(parallel to) = 2.017, g(perpendicular to) = 2.003) for electrogenerated [Os(CN)(5)(NO)](3-) does not reflect any effect from the 5d element osmium with its high spin-orbit coupling constant; only the need to apply helium temperatures for EPR signal observation indicates the presence of a heavy transition metal. (C) 1999 Elsevier Science S.A. All rights reserved.