Eightfold Electrophilic Methylation of Octacyanotungstate [W(CN)8]4-/3-: Preparation of Homoleptic, Eight-Coordinate Methyl Isocyanide Complexes [W(CNMe)8]4+/5.

Homoleptic eightfold coordinated methyl isocyanide complexes of W(IV) and W(V) have been prepared for the first time. The reaction of [NBu4]4[W(CN)8] with methyl triflate (MeOTf) gives [W(CNMe)8][OTf]4. The even stronger methylating mixture of methyl fluoride (MeF) and arsenic pentafluoride (AsF5) in liquid sulfur dioxide (SO2) is able to fully alkylate both [NBu4]4[W(CN)8] and [NBu4]3[W(CN)8]. The paramagnetic octakis(methyl isocyanide)tungsten(V) complex [W(CNMe)8][AsF6]5 is thermally highly unstable above -30 °C. All compounds have been characterized via single-crystal X-ray diffraction and IR, Raman, and NMR or EPR spectroscopy.