CHROMIUM CARBON MULTIPLE BONDS - AMINOCARBYNE COMPLEXES OF CHROMIUM BEARING ISOCYANIDE LIGANDS

High yield syntheses of neutral and cationic aminocarbyne complexes of chromium-bearing isocyanide ligands are reported. Neutral complexes o f the type Br(CO)(2)(RNC)(2)Cr=(CNPr2)-Pr-i(R = Et (3a); R = (t)Bu (3b )) are obtained from Br(CO)(2)(pic)(2)Cr=(CNPr2)-Pr-i (2) (pic = gamma -picoline) by exchange of the gamma-picoline ligands with RNC, Complex 3b reacts with (t)BuNC in toluene at 60 degrees C to give the monocar bonyl derivative Br(CO)((t)BuNC)(3)Cr=(CNPr2)-Pr-i (4b). Formation of cationic aminocarbyne complexes is favoured in polar solvents as demon strated by the reaction of 3a or 3b with RNC in refluxing CH2Cl2 which leads exclusively to [(RNC)(4)(CO)Cr=(CNPr2)-Pr-i]Br (R = Et (5a); R = (t)Bu (5b)). Thermal decarbonylation of 5b with (t)BuNC in refluxing tetrahydrofuran (THF) affords the cationic aminocarbyne complex [((t) BuNC)(5)Cr=(CNPr2)-Pr-i]Br (7b), Similarly, 3b is converted with TIPF6 and (t)BuNC to [((t)BuNC)(3)(CO)(2)Cr=(CNPr2)-Pr-i]PF6 (6b), which re acts with (t)BuNC in refluxing THF to give [((t)BuNC)(5)Cr=(CNPr2)-Pr- i]PF6 (7b').