Novel cationic monobut-2-yne complexes of tungsten(II) containing dithiocarbamates and related ligands

Article abstract of DOI:10.1016/0022-328X(90)85314-O

Equimolar quantities of 2-MeC2Me)> (dppm = Ph2P(CH2)PPh2) and MS2CX (M = Na, X = NMe2; M = Na, X = NEt2; M = , 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 2-MeC2Me)>I.The complex 2-MeC2Me)>I can also be prepared by reacting equimolar quantities of 2-MeC2Me)> with (S2CNC4H8> in refluxing chloroform.Both these types of reaction involve the formation of the monodentate dithiocarbamate intermediates 1-S2CX)(CO)(dppm)(η²-MeC2Me)>.Reaction of 2-MeC2Me)> and MS2CX in a 2:1 molar ratio afforded a mixture of the cationic monobut-2-yne complexes 2-MeC2Me)> and 2-MeC2Me)>.Variable temperature 1H NMR studies carried out on 2MeC2Me)>I showed the complex to be fluxional.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 2-MeC2Me)>I is donating four electrons to the tungsten in these compounds.