Dibromoalkyne complexes of tungsten(II)

Abstract Treatment of [WBr 2 (CO) 3 (NCMe) 2 ] with an excess of MeC 2 Me or two equivalents of RC 2 R (R = Ph or CH 2 Cl) in CH 2 Cl 2 at room temperature gave the bis(alkyne) complexes [WBr 2 (CO)(NCMe)(η 2 -RC 2 R) 2 ]. Two equivalents of PPh 2 Cy reacts with [WBr 2 (CO)(NCMe)(η 2 -MeC 2 Me) 2 ] to afford the bis(phosphine) complex [WBr 2 (CO) (PPh 2 Cy) 2 (η 2 -MeC 2 Me)]. Equimolar quantities of [WBr 2 (CO)(NCMe)(η 2 -MeC 2 Me) 2 ] and L ∧ L [L ∧ L = Ph 2 P(CH 2 ) n PPh 2 ( n = 1−6) or 2,2′-bipy] react in CH 2 Cl 2 at room temperature to give either [WBr 2 (CO)[Ph 2 P(CH 2 ) n PPh 2 ](η 2 -MeC 2 Me)] or [WBr(CO)(2,2′ bipy) (η 2 -MeC 2 Me) 2 ]Br, respectively. The cationic nature of [WBr(CO)(2,2′-bipy)(η 2 -MeC 2 Me) 2 ]Br was confirmed by reaction with Na[BPh 4 ] in acetonitrile to give [WBr(CO)(2,2′-bipy)(η 2 -MeC 2 Me) 2 ][BPh 4 ]. The barrier to but-2-yne rotation of selected mono(but-2-yne) complexes was determined by using variable temperature 1 H NMR spectroscopy. 13 C NMR spectroscopy was used to suggest the number of electrons donated to the metal for selected complexes.