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

Abstract

Aryldiazo complexes, [M(CO)$sub 2$(NNPh)(PPh$sub 3$)$sub 2$][PF$sub 6$](M = Os, Ru; Ph = C$sub 6$H$sub 5$), were prepared by allowing diazonium salts to react with M(CO)$sub 3$(PPh$sub 3$)$sub 2$. 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$sup -$), to form MX(CO)$sub 2$(NNPh)(PPh$sub 3$)$sub 2$. The osmium derivatives have $nu$(NN) near 1455 cm$sup -1$, which is the lowest value yet reported for a nonbridging aryldiazo ligand. The first aryldiazo--hydrido complexes, MH(CO)$sub 2$(NNPh)(PPh$sub 3$)$sub 2$ and MH(CO)(NNPh)(PPh$sub 3$)$sub 2$, were prepared by deprotonation of the respective phenyldiazene complexes, MH(CO)$sub 2$(HNNPh)(PPh$sub 3$)$sub 2$$sup +$ and MH(CO)(HNNPh)(PPh$sub 3$)$sub 3$$sup +$. The compound OsCl$sub 3$(NNPh)(PPh$sub 3$)$sub 2$ was also prepared. A large number of the foregoing complexes were synthesized with selective $sup 2$H and $sup 15$N labels. Infrared and NMR spectra show MX(CO)$sub 2$(NNPh)(PPh$sub 3$)$sub 2$ and the analogous hydrido complex to be pseudooctahedral with trans phosphine ligands, cis carbonyl ligands, and a doubly bent phenyldiazenido (NNPh$sup -$) ligand. Similarly, MH(CO)(NNPh)(PPh$sub 3$)$sub 2$ possesses a trigonal-bipyramidal geometry with trans phosphine ligands and an equatorial, singly bent phenyldiazoniumato (NNPh$sup +$) ligand. Isotopic substitution of the diazo ligand shows that $nu$(NN) is often vibrationally coupled with phenyl vibrational modes and that two or three bands sometimes shift upon $sup 15$N substitution. Vibrational coupling was also observed in the higher energy region (1850 to 1900 cm$sup -1$) in the compound RuCl$sub 3$(NNC$sub 6$D$sub 5$)(PPh$sub 3$)$sub 2$. The wide range in the values of $nu$(NN), RuCl$sub 3$(NNPh)(PPh$sub 3$)$sub 2$ (1882 cm$sup -1$) vs. RuCl(CO)$sub 2$(NNPh)(PPh$sub 3$)$sub 2$ (1462 cm$sup -1$), 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. (auth)