1 An efficient approach to the ammoxidation of alcohols to nitriles and the aerobic oxidation of alcohols to aldehydes in water using Cu(II)/pypzacac complexes as catalysts

摘要

Reactions of 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl)acetic acid (pypzacacH) ligand with Cu(OAc)(2), Cu(NO3)(2), CuSO4, Cu(ClO4)(2) or CuCl2 produced four dinuclear Cu(II) complexes [{(MeOH)Cu(OAc)}(mu-kappa(2):kappa(1)-pypzacac)](2)center dot 0.5H(2)O (1.0.5H(2)O), [{Cu(pypzacac)}(mu-kappa(2):kappa(1)-pypzacac)(2){Cu(H2O)(2)}](NO3)center dot 2(MeOH)(0.5)center dot 6H(2)O (2.2(MeOH)(0.5)center dot 6H(2)O), [{(MeOH)Cu(mpypzacac)}(mu-SO4)](2)center dot 2MeOH (3.2MeOH; mpypzacac = methyl 2-(3-(pyridin-2-yl)-1H-pyrazol-1-yl)acetate), [{Cu(mpypzacac)(2)}(mu-kappa(2):kappa(1)-pypzacac){Cu(mpypzacac)}](ClO4)(3)center dot MeOH (4 center dot MeOH) and one polymeric Cu(II) complex [(CuCl)(mu-kappa(3):kappa(1)-pypzacac)](n) (5), respectively. The mpypzacac ligand in 3 and 4 was in situ generated via the Cu2+-catalyzed dehydrative esterification of acetic acid of the pypzacacH ligand. Complexes 1-5 are characterized by elemental analysis, IR and single-crystal X-ray diffraction. Complex 1 contains two {(MeOH)Cu(OAc)} fragments that are interconnected by two mu-kappa(2):kappa(1)-pypzacac(-) ligands, forming a dimeric structure. In 2, {Cu(pypzacac)} and {Cu(H2O)(2)} units are bridged by a pair of mu-kappa(2):kappa(1)-pypzacac(-) ligands. In 3, two {Cu(mpypzacac)} fragments are linked by two mu-kappa(1):kappa(1)-SO42- ions to form a dinuclear structure. Complex 4 also adopts a dimeric structure in which {Cu(mpypzacac) 2} and {Cu(mpypzacac)} units are interconnected by one mu-kappa(3):kappa(1)-pypzacac(-) ligand. Complex 5 contains a 1D chain in which (CuCl) fragments are interlinked by mu-kappa(3):kappa(1)-pypzacac(-) ligands. Complexes 1-5 exhibited excellent catalytic performance in the ammoxidation of alcohol to nitrile and the aerobic oxidation of alcohol to aldehyde in water. The catalytic aqueous solution was easily separated and could be reused for several cycles without any obvious decay of catalytic efficiency.