Phenyldiazene Complexes. Structure and Spectra of Chlorodicarbonyl(cis-phenyldiazene)bis(triphenylphosphine)ruthenium(II) Perchlorate Methylene Chloride Solvate

The structure of [RuCl(CO)₂(HN₂C₆H₅)(P(C₆H₅)₃)₂] [CIO₄]·CH₂Cl₂ has been determined by X-ray diffraction methods. The compound crystallizes from methylene chloride as solvated crystals in space group C_2h⁵− P2₁)/c with four formula units in a cell of dimensions a = 11.801 (5) Å, b = 17.752 (8) Å, c = 22.938 (11) Å, and β = 110.96 (2)°. Based on 5074 unique reflections with F_o²> 3σ(F_o²), the structure has been solved and refined by full-matrix, least-squares methods to an R index (on F) of 0.053. The structure consists of discrete ions and solvent molecules. The ruthenium cation is six-coordinate, with trans phosphine ligands and cis carbonyl ligands. The phenyldiazene ligand adopts the cis configuration about the N-N double bond and is bound in a fashion through N(1) to the metal. The positional parameters of the nonaromatic diazene proton were refined. Important angles and distances are Ru-N(1) =2.086 (5) Å, N(1)-N(2) = 1.218 (7) Å, N(1)-H = 1.00 (6) Å, N(2)-C(phenyl) = 1.409 (6) Å, [formula ommited]Ru-N(1)-N(2) = 129.2 (5)°, [formula ommited]Ru-N(1)-H = 128 (4)°,[formula ommited]H(1)-N(1)-N(2) = 102 (4)°, and [formula ommited]N(1)-N(2)-C(phenyl) = 118.2 (5)°. The short, nonbonded contact between the nonaromatic diazene proton and an ortho-phenyl proton causes considerable rotation of the phenyl group about the N-C bond. Spectroscopic and structural data suggest that phenyldiazene behaves as a normal -donor ligand without significant π-bonding characteristics. The N-N stretching frequencies for PtCl(HN₂C₆H₅)(P(C₂H₅)₃)₂⁺, the title complex, and their respective deprotonated analogs are shown to be coupled with vibrational modes of the phenyl groups. The values of ν(NN) for the diazenido complexes are shown to be lower than those for the corresponding diazene complexes.