Illusive tungsten-imido-dithiocarbamate complexes: Facile carbon–nitrogen bond formation

Heating [WO2(S2CNBui2)2] with a slight excess of ArNCO (Ar = Ph, p-tolyl) results in the rapid formation of imido-ureato complexes [W(NAr){κ2-ArNC(O)NAr}(S2CNBui2)2], a transformation believed to occur via the bis(imido) intermediates [W(NAr)2(S2CNBui2)2]. The ureato ligand is easily removed (as the urea) upon addition of gaseous HCl to afford the dichloride [W(NAr)Cl2(S2CNBui2)2]. While bis(imido) complexes are unavailable from the direct reaction of isocyanates (or amines) with [WO2(S2CNBui2)2], they can be prepared upon addition of dithiocarbamate salts to [W(NBut)2(NHBut)2] addition of two equivalents of [NH2Bui2][Bui2NCS2] affording [W(NBut)2(S2CNBui2)2] in which both imido groups are linear.