Reactivity of the iridium nitrosyl complex [Ir(NO)(paa)(PPh3)2][PF6]2(paa = 2-pyridinecarbaldehyde azine) with nucleophiles: insertion of NO into a methinic C–H bond; crystal structure of [Ir{(2-C5H4N)CHN–NC(NOH)(2-C5H4N)}{Me-(EtO)CNH}(PPh3)2][PF6]2

Abstract

The nitrosyl complex [Ir(NO)(paa)(PPh₃)₂][PF₆]₂(paa = 2-pyridinecarbaldehyde azine) reacts either with RCN (R = Me, Ph, or Ph₂CH) or X^–(X = Cl or SCN) at room temperature, to give cyclometallated compounds containing the I[graphic omitted](OH) moiety. These complexes were characterised by elemental analysis, conductivity measurements, i.r. and n.m.r. spectroscopy. The metallated ring can be envisaged as resulting from intramolecular insertion of the NO group, activated by the iridium co-ordination of RCN or X^–, into the methinic C–H bond of the unco-ordinated paa fragment. Addition of ethanol to the compound containing MeCN or PhCN gives imidate complexes. The structure of the acetoimidate complex [Ir{(2-C₅H₄N)CHN–NC(NOH)(2-C₅H₄N)}(Me(EtO)CNH}(PPh₃)₂][PF₆]₂ has been determined by X-ray diffraction. Crystals are monoclinic, space group Cc, with unit-cell dimensions a= 12.405(6), b= 43.836(12), c= 11.126(7)Å, β= 112.1(2)°, and Z= 4. The structure has been solved from diffractometer data by Patterson and Fourier methods and refined by block-matrix least squares to final R and R′ values of 0.057 and 0.073 for 3 394 observed reflections. In the cation four N atoms, one from the neutral ethylacetoimidate ligand and the other three from the monoanionic ligand resulting by intramolecular insertion of NO into a methinic C–H bond of the starting paa ligand, are arranged in the equatorial positions of the iridium co-ordination octahedron whose apices are occupied by P atoms from PPh₃ molecules. The new [graphic omitted] fragment displays a C–N bond length of 1.37(3)Å and the OH group is involved in a strong intramolecular hydrogen bond with the unco-ordinated pyridyl nitrogen atom.