Synthesis and characterisation of {Mo(eta-L)(CO)(3)}(+) (eta-L = C5H5 or C5Me5) fragments ligated with [CB11H12](-) and derivatives. Isolation and structural characterisation of an intermediate in a silver salt metathesis reaction

The synthesis of {Mo(eta -L)(CO)(3)}(+) (eta -L = C5H5 or C5Me5) fragments, ligated to the mono-anionic, weakly co-ordinating, carboranes [closo-1-CB11H12](-) and [closo-CB11Br6H6](-), has been investigated. Treatment of [MoCp(CO)(3)X] (X = Cl or I) with Ag[CB11H12] eventually affords the zwitterionic complex [MoCp(CO)(3)(x-mu -H-1-CB11H12)] (x = 12 or 7), via an intermediate dimeric species [MoCp(CO)(3)X . Ag(CB11H12)](2). For X = I this intermediate has been characterised by H-1, B-11 NMR spectroscopy and X-ray crystallography and represents the first structurally characterised intermediate in a silver salt metathesis reaction. When the less nucleophilic carborane [CB11Br6H6](-) (as its silver salt) is used metathesis is halted at the intermediate stage, affording the complex [MoCp(CO)(3)I . Ag(CB11Br6H6)](2). Silver salt metathesis does not proceed using the sterically more demanding [Mo(Cp*)(CO)(3)I], with only intractable products isolated. The carborane anion can be introduced into the co-ordination sphere of this complex by reaction of [H(OEt2)(x)][CB11H12] with [Mo(Cp*)(CO)(3)Me] affording [Mo(Cp*)(CO)(3)(x-mu -H-1-CB11H12)] (x = 12 or 7). All new compounds have been characterised by multinuclear NMR spectroscopy and X-ray crystallography.