HEAVIER HALIDES OF EARLY TRANSITION-ELEMENTS BY HALIDE-EXCHANGE REACTIONS - CRYSTAL AND MOLECULAR-STRUCTURE OF [PH3C]2[HF2CL10]

Abstract: The decahalogenodimetalates of zirconium(IV) and hafnium(IV) as their triphenylmethyl derivatives [Ph3C]2[M2Cl10] have been obtained by the reaction of M(BH4)4 with the appropriate Ph3CX or by addition of Ph3CX to MX4. The crystal and molecular structure of [Ph3C]2[Hf2Cl10] has been studied by X-ray diffraction methods: triclinic, space group P, a= 15.965(3), b= 12.907(3), c= 10.526(3)Å, α= 99.75(2), β= 84.84(2), γ= 102.64(2)°, and Z= 2. The structure consists of [Ph3C]+ cations and [Hf2Cl10]2– anions, the latter having crystallographic symmetry. The chloride-bridged dimers have a distorted octahedral co-ordination while the [Ph3C]+ cations have a trigonal-planar geometry around the central carbon. The heavier halides of niobium(V) and tantalum(V) have been prepared from the chlorides by exchange reactions with PriBr (in the case of NbBr5) or with HX in EtBr solution (in the cases of NbI5 and TaX5).