Synthesis and spectroscopic structural elucidation of five-coordinate homo- and heterometal1ic complexes of aluminium(III)

Equi molar reactions of Schiff bases (HL) and β-ketoamines(HL*) with Al(OPr i ) 3 in benzene afford mixed-ligand cyclic five-coordinate aluminium complexes of the type [Al(η 2 -L) (η 2 -L*)(OPr i )] (where L = L 1 , L* = L 3 (1) and L = L 2 , L* = L 4 (2)), in which the deprotonated forms of Schiff base OC 6 H 4 CH=NCH(CH 3 )Et (L = L 1 ) and OC 10 H 6 CH=NC 6 H 3 (CH 3 ) 2 -2,6 (L = L 2 ) as well as β-ketoamines OC(CH 3 )=CHC(CH 3 )=NR(R=Et(L*= L 3 ), R=C 6 H 3 (CH 3 ) 2 -2,6 (L* = L 4 )) are bonded to aluminium in a bidentate (η 2 ) fashion through O, N donor atoms. The complexes (1) and (2) on reaction with hexylene glycol (abbreviated as HOGOH) afford complexes of the type [Al(η 2 -L)(η 2 -L*)(OGOH)] (3) (L = L 1 , L* = L 3 ) and (4) (L = L 2 , L* = L 4 ) containing three entirely different organic moieties. The latter two complexes on reaction in 1:1 molar ratio in benzene with B(OPr i ) 3 , Ti(OPr i ) 4 , and Nb(OPr i ) 5 afford novel heterobimetallic complexes of the type [Al(η 2 -L)(η 2 -L*) {OGOM(OPr i ) n- }] (5, M = B, n = 3, L = L 1 , L* = L 3 ; 6, M = B, n = 3, L = L 2 , L* = L 4 ; 7, M = Ti, n = 4, L = L 1 , L* = L 3 ; 8, M = Ti, n = 4, L = L 2 , L* = L 4 ; 9, M = Nb, n = 5, L = L 1 , L* = L 3 ; 10, M = Nb, n = 5, L = L 2 , L* = L 4 ). All these homo- and heterometallic derivatives have been characterized by elemental analysis, molecular weight measurements, IR and NMR ( 1 H, 22 Al, and 13 C) spectral studies and plausible structures have been suggested.