Synthesis, characterization and protonation reaction of copper and palladium complexes bearing nitrite ligands in O,O-bidentate and N-monodentate bonding fashions

Cu(Ph(2)P(o-C(6)H(4)C(=O)H))(2)(NO(2)) (3) has been prepared in high yield by treating [Cu(Ph(2)P(o-C(6)H(4)C(=O)H))(2)(NCMe)]BF(4) (2) with [Ph(2)PNPPh(2)]NO(2) at ambient temperature. The nitrite ligand of 3 is coordinated to the Cu(I) center in an O,O-bidentate mode. Protonation of 3 releases NO molecule, which mimics the reactivity of the Type 2 Cu-NiRs. In contrast, reaction of [Pd(NCMe)(4)](BF(4))(2) and Ph(2)P(o-C(6)H(4)C(=O)H) affords cis-[Pd(Ph(2)P(o-C(6)H(4)C(=O)H))(2)](BF(4))(2) (4) with the Pd(2+) ion chelated by two phosphino-aldehyde moieties. The hemilabile formyl ligands of 4 can be displaced by NO(2) to produce trans-Pd(Ph(2)P(o-C(6)H(4)C(=O)H))(2)(NO(2))(2) (5), of which the nitrite ligands present an N-monodentate bonding feature. Protonation of 5 with HBF(4), however, regenerates compound 4, likely via elimination of nitrous acid. The structures of 3-5 have been determined by an X-ray diffraction study. (C) 2011 Elsevier B.V. All rights reserved.