Synthetic pathways in binuclear molybdenum chemistry: µ-acetato-, chloro-, and tertiary phosphine derivatives; X-ray structure determination of trans-[{MoCl(PBun3)(µ-O2CMe)}2]

Abstract

The reaction between [{Mo(µ-OCOMe)₂}₂] and SiMe₃Cl in the presence of a variety of donor ligands L [tetrahydrofuran (thf), Me₂S, Et₂S, PEt₃, PPh₃, PBuⁿ₃, or Ph₂P(CH₂)_nPPh₂, where n= 1 or 2] yields binuclear compounds such as [{MoLCl(µ-OCOMe)}₂] or [(MoL₂Cl₂)₂]. The products may vary according to the stoicheiometry of the reaction. The new compounds described are [{MoCl(µ-OCOMe)(thf)}₂], [{MoCl₂(PPh₃)(µ-OCOMe)}₂], isomers of [{MoCl(PEt₃)(µ-OCOMe)}₂], trans-[{MoCL(PBuⁿ₃)(µ-OCOMe)}₂], and [Mo₂Cl₂(OCOMe)₂(dppm)]. Interconversion of some of these compounds by ligand-replacement reactions is also demonstrated. The crystal structure of trans-[{MoCl(PBuⁿ₃)(µ-OCOMe)}₂] is described; the crystals are monoclinic, space group P2₁/n, with a= 14.969(2), b= 15.146(2), c= 8.920(2)Å, β= 105.14(1)°, and Z= 2. Refinement converged with R= 0.048, R′= 0.063, for 1 762 observed reflections [l > 3σ(l)]. The Mo–Mo separation is 2.099(1)Å. The presence of isomers of the various compounds is demonstrated from the hydrogen-1 n.m.r. spectra.