4-AminobenzyIidyne: A versatile precursor for extended unsaturated alkylidyne ligandsf

The 4-aminobenzylidyne tungsten complexes [W(CC6H4NH2-4)X(CO)2(pic)2] 1 (X = Cl a or Br b) have been prepared by sequential reaction of [W(CO)6] with LiC6H4N(SiMe3)2-4 in diethyl ether and C2O2C12 or C2O2Br2 and 4-methylpyridine (pic) in CH2C12. Substitution of the picoline ligands by tmen (Me2NCH2CH2NMe2) and dppe (Ph2PCH2CH2PPh2) afforded the complexes [W(CC6H4NH2-4)X(CO)2(L2)] (L2 = tmen 2, X = Cl a or Br b; dppe 3, X = Cl a or Br b). The amino group of the new alkylidyne complexes undergoes typical functional group transformations. Treatment of complexes 2 with pyridine-2-carbaldehyde afforded the Schiff-base derivatives [W{CC6H4(NCHC5H4N-2)-4}X(CO)2(tmen)] 5 (X = Cl a or Br b). Formylation of complexes 2 with acetic formic anhydride afforded the formamides [W(CC6H4NHCHO-4)X(CO)2(tmen)] 6 (X = Cl a or Br b). The isocyanide derivatives [W(CC6H4NC-4)X(CO)2(tmen)] 11 (X = Cl a or Br b) were obtained by dehydration of complexes 6 with triphosgene-NEtj. The molecular structures of 3a, 4b, 8a, 9a and lOb were determined by X-ray crystallography.