Aryldiazo complexes. Syntheses and reactions of new complexes of osmium and ruthenium

Article abstract of DOI:10.1021/ic50153a038

Aryldiazo complexes, [M(CO)₂(NNPh)(PPh₃)₂][PF₆] (M = Os, Ru; Ph = C₆H₅), have been prepared by allowing diazonium salts to react with M(CO)₃(PPh₃)₂. Infrared spectra of the Ru complex suggest the presence of two isomers both in solution and in the solid state. These complexes react with a variety of coordinating anions (X^-), to form MX(CO)₂(NNPh)(PPh₃)₂. The osmium derivatives have ν(NN) near 1455 cm^-1, which is the lowest value yet reported for a nonbridging aryldiazo ligand. The first aryldiazo-hydrido complexes, MH(CO)₂(NNPh)(PPh₃)₂ and MH(CO)(NNPh)(PPh₃)₂, were prepared by deprotonation of the respective phenyldiazene complexes, MH(CO)₂(HNNPh)(PPh₃)₂⁺ and MH(CO)(HNNPh)(PPh₃)₃⁺. The compound OsCl₃(NNPh)(PPh₃)₂ has also been prepared. A large number of the foregoing complexes have been synthesized with selective ²H and ¹⁵N labels. Infrared and NMR spectra show MX(CO)₂(NNPh)(PPh₃)₂ and the analogous hydrido complex to be pseudooctahedral with trans phosphine ligands, cis carbonyl ligands, and a doubly bent phenyldiazenido (NNPh^-) ligand. Similarly, MH(CO)(NNPh)(PPh₃)₂ possesses a trigonal-bipyramidal geometry with trans phosphine ligands and an equatorial, singly bent phenyldiazoniumato (NNPh⁺) ligand. Isotopic substitution of the diazo ligand shows that ν(NN) is often vibrationally coupled with phenyl vibrational modes and that two or three bands sometimes shift upon ¹⁵N substitution. Vibrational coupling is also observed in the higher energy region (1850-1900 cm^-1) in the compound RuCl₃(NNC₆D₅)(PPh₃)₂. The wide range in the values of ν(NN), RuCl₃(NNPh)(PPh₃)₂ (1882 cm^-1), vs. RuCl-(CO)₂(NNPh)(PPh₃)₂ (1462 cm^-1), indicates that the N-N stretching frequencies are sensitive to the electronic and steric environment of the diazo ligand. The aryldiazo complexes are compared with analogous, isoelectronic nitrosyl complexes of Os and Ru.