Syntheses, characterization and X-ray structures of gold(III) complexes obtained by addition of bases to gold(III)(2-pyridinecarboxaldehyde)

Reaction of potassium tetrachloroaurate(III), KAuCl4, with 2-pyridinecarboxaldehyde (2CHO-py) have been examined in protic HX (X=OH, OMe, OEt, OCH2CH2CH3, OCH2CH2CH2CH3, OCH2CF3) solvents. Compounds in which the pyridine ligand is N or N-O coordinated in a newly carbonyl hydrated or in semi- and acetal-forms, derived by addition of one or two hydroxylic molecules, have been isolated; these include dichloro[pyridine-2(alpha-hydroxymethanolato)]gold(III) (1), dichloro[pyridine-2(alpha-ethoxymethanolato)] gold(III) (2), dichloro[pyridine-2[alpha-(2,2,2-trifluoroethoxymethanolato)]gold(III) (3), trichloro(2-pyridinecarboxaldehyde dimethyl acetal)gold(III) (4), trichloro(2-pyridinecarboxaldehyde diethyl acetal)gold(III) (5), trichloro(2-pyridinecarboxaldehyde di-1-propyl acetal)gold(III) (6) and trichloro(2-pyridinecarboxaldehyde di-1-butyl acetal)gold(III) (7). The crystal and molecular structures of (2), (5) and (7) have been determined by X-ray methods. Compound (2) crystallizes in space group Pna2(1) with Z = 4, a = 7.8914(4), b = 17.3660(4) and c=8.387 (5)Angstrom; (5) crystallizes in space group P (1) over bar with Z=2, a=7.7779(3), b=8.2878(2) and c=13.3202(6)Angstrom, alpha=96.975(2), beta=95.096(2), gamma=115.02.7(2)degrees; (7) crystallizes in space group P2(1)/a with Z = 4, a = 14.5438(12), b = 8.9865(7) and c = 15.0362(11)Angstrom.