title: Reactivity of the hydrido/nitrosyl radical MHCl(NO)(CO)(P(i)Pr(3))(2), M = Ru, Os.
abstract: The reaction of equimolar NO with the 16 electron molecule RuHCl(CO)L(2) (L = P(i)Pr(3)) proceeds, via a radical adduct RuHCl(CO)(NO) L(2), onward to form RuCl(NO)(CO)L(2) (X-ray structure determination) and RuHCl(HNO)(CO)L(2), in a 1:1 mole ratio. The HNO ligand, bound by N and trans to hydride, is rapidly degraded by excess NO. The osmium complex behaves analogously, but the adduct has a higher formation constant, permitting determination of its IR spectrum; both MHCl(CO)(NO)L(2) radicals are characterized by EPR spectroscopy, and DFT calculations on the Ru system show it to have a "half-bent" Ru-N-O unit with the spin density mainly on nitrogen. DFT (PBE) energies rule out certain possible mechanistic steps for forming the two products. A survey of the literature leads to the hypothesis that NO should generally be considered as a (neutral) Lewis base (2-electron donor) when it binds to a 16 electron complex which is resistant to oxidation or reduction, and that the resulting N-centered radical has a M-N-O angle of approximately 140 degrees, which distinguishes it from NO(-) (bent at <140 degrees ) and from NO(+) (>170 degrees ).
authors.affiliation: Indiana University, Department of Chemistry, Bloomington, Indiana 47405, USA.
authors.forename: Alexei V
authors.initials: AV
authors.lastname: Marchenko
authors.forename: Andrei N
authors.initials: AN
authors.lastname: Vedernikov
authors.forename: David F
authors.initials: DF
authors.lastname: Dye
authors.forename: Maren
authors.initials: M
authors.lastname: Pink
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Zaleski
authors.forename: Kenneth G
authors.initials: KG
authors.lastname: Caulton