Insertion of Carbon Monoxide into Nickel-Alkyl Bonds of Monoalkyl-and Dialkylnickel(II) Complexes, NiR(Y)L2 and NiR2L2. Preparation of Ni(COR)(Y)L2 from NiR(Y)L2 and Selective Formation of Ketone, Diketone, and Aldehyde from NiR2L2

Abstract

Abstract Reactions of monoalkylnickel(II) complexes, NiR(Y)L2 (R=CH3, C2H5; Y=Cl, suc(succinimido), pht(phthalimido), OC6H4-p-CN; L=1/2 bpy (2,2′-bipyridine), PEt3 (triethylphosphine)), with CO afford monoacylnickel(II) complexes, Ni(COR)(Y)L2, which are characterized by elemental analysis and spectroscopies (IR and NMR). Reactions of the acylnickel(II) complexes with alcohols and aniline give the corresponding esters and amides, respectively. Exposure of Ni(COR)(Y)L2 to dry air leads to oxidation of RCO to a RCOO ligand giving a complex formulated as Ni(OCOR)(Y)L2. Reactions of dimethylnickel(II) complexes, Ni(CH3)2L2 (L=1/2 bpy, PEt3, 1/2 dpe (1,2-bis(diphenylphosphino)ethane, 1/2 dpp (1,3-bis(diphenylphosphino)propane), with carbon monoxide afford acetone and/or 2,3-butanedione in medium to high yields, the acetone/2,3-butanedione ratio varying with the ligand L, reaction temperature, and additives such as maleic anhydride and triphenylphosphine. Generally the acetone/2,3-butanedione ratio decreases with increase in thermal stabilities of Ni(CH3)2L2. Ni(C2H5)2(bpy) and Ni(n-C3H7)2(bpy) give 3-pentanone and 4-heptanone, respectively, on treating them with CO, whereas Ni(C2H5)2(dpe) produces C2H5CHO and C2H4.