NOVEL CATIONIC MONOBUT-2-YNE COMPLEXES OF TUNGSTEN(II) CONTAINING DITHIOCARBAMATES AND RELATED LIGANDS

Equimolar quantities of [WI(CO)(NCMe)(dppm)(η2-MeC2Me)][BF4] (dppm = Ph2P(CH2)PPh2) and MS2CX (M = Na, X = NMe2; M = Na, X = NEt2; M = [NH4], X = NC4H8; M = Na, X = N(CH2Ph)2; or M = K, X = OEt) react in CH2Cl2 at room temperature to eventually give the cationic monobut-2-yne complexes [W(CO)(S2CX)(dppm)η2-MeC2Me)]I. The complex [W(CO)(S2CNC4H8)-(dppm)(η2-MeC2Me)]I can also be prepared by reacting equimolar quantities of [WI2(CO)(dppm)(η2-MeC2Me)] with [NH4][S2CNC4H8] in refluxing chloroform. Both these types of reaction involve the formation of the monodentate dithiocarbamate intermediates [WI(η1-S2CX)(CO)(dppm)(η2-MeC2Me)]. Reaction of [WI(CO)(NCMe)(dppm)(η2-MeC2Me)][BF4] and MS2CX in a 2 : 1 molar ratio afforded a mixture of the cationic monobut-2-yne complexes [W(CO)(S2CX)(dppm) (η2-MeC2Me)][BF4] and [WI2(CO)(dppm)(η2-MeC2Me)]. Variable temperature 1H NMR studies carried out on [W(CO)(S2CNEt2)(dppm)(η2-MeC2Me)]I showed the complex to be fluixonal. The barrier to but-2-yne rotation was calculated to be 49.7 ∓ 1 kJ mol-1. 13C NMR studies show the but-2-yne ligand in [W(CO) (S2CX)(dppm)(η2-MeC2Me)]I is donating four electrons to the tungsten in these compounds. © 1990.