Reactions between oximes and organo-derivatives of Group III elements. Part II. Pyridine-2-carbaldehyde oxime

Abstract

Pyridine-2-carbaldehyde oxime reacts with trimethylborane in toluene at 90° to form methane and the crystalline oximate (2-C₄H₃N)CH:NOBMe₂, which is monomeric in benzene. The structure (IX) postulated for this derivative has the oximate residue in the anti-configuration attached to four-co-ordinate boron through the oxime oxygen and pyridine nitrogen. Alkyl groups are more readily cleaved from Me₃Al, Et₃Al, Me₃Ga, Me₃In, and Me₃Tl by pyridine-2-carbaldehyde oxime at or below 0°, with formation of oximates [(2-C₅H₄N)CH:NOMR₂]_n, which are generally dimeric (n= 2) in benzene. ¹H N.m.r. and i.r. spectroscopic data are presented in support of fused-ring structures (VIII) for these dimers, incorporating central ‘MONMON’ rings, with the oximate residues in the syn-configuration attached through oxygen to one metal atom, and through both nitrogen atoms to the other metal atom, of the dimer. The metal atoms are believed to be five-co-ordinate. Trimethylaluminium and syn-benzaldehyde oxime apparently form (PhCH:NOAlMe₂)_n.