PPh3Me[MoBr5(CH3CN)]. IR-Spektrum,magnetisches Verhalten und Kristallstruktur

PPh₃MeMoBr₅(CH₃CN)]. I.R. Spectrum, Magnetic Behaviour, and Crystal Structure Molybdenum tetrabromide and acetonitrile form MoBr₄(CH₃CN)₂, from which PPh₃MeMoBr₅(CH₃CN)] is obtained by reaction with PPh₃MeBr in dibromo methane. Both compounds are characterized by their IR spectra. By evaluation of the magnetic susceptibility of PPh₃MeMoBr₅(CH₃CN)] in the temperature range of 4.2 to 290 K the Curie-Weiss parameters μ_cw = 2.65 B.M. and Θ = ?44 K were obtained. The crystal structure of PPh₃MeMoBr₅(CH₃CN)] was determined by X-ray diffraction (2426 observed reflexions, R = 0.082). Crystal data: a = 1064.9, b = 2172.1, c = 1330.4 pm, β = 119.92º, space group P2₁/c, Z = 4. In the crystal, PPh₃Me⁺ and MoBr₅(CH₃CN)]^? ions are packed in alternate cation and anion layers perpendicular to a. In the anion the Mo atom has a distorted octahedral coordination. The bond length of the bromine atom in trans position to the N atom is considerably shorter than the other MoBr distances.