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

Abstract

Equimolar reactions of Schiff bases (HL) and β-ketoamines(HL*) with Al (OPrⁱ)₃ in benzene afford mixed-ligand cyclic five-coordinate aluminium complexes of the type [Al(η²-L) (η²-L*)(OPrⁱ) ] (where L = L¹, L* = L³ (<b>1</b>) and L = L², L* = L⁴ (<b>2</b>)), in which the deprotonated forms of Schiff base OC₆H₄CH=NCH(CH₃)Et (L = L^l) and OC₁₀H₆CH = NC₆H₃(CH₃)₂ -2,6 (L = L²) as well as β-ketoamines OC(CH₃)=CHC(CH₃)=NR(R=Et (L* = L³), R= C₆H₃(CH₃)₂ -2,6 (L* = L⁴)) are bonded to aluminium in a bidentate (η²) fashion through O, N donor atoms. The complexes (<b>1</b>) and (<b>2</b>) on reaction with hexylene glycol (abbreviated as HOGOH) afford complexes of the type [Al (η²-L)(η²-L*)(OGOH )] (<b>3</b>) (L = L¹, L* = L³) and (<b>4</b>) (L = L², L* = L⁴) containing three entirely different organic moieties. The latter two complexes on reaction in 1:1 molar ratio in benzene with B(OPrⁱ)₃,Ti (OPrⁱ)₄ , and Nb(OPrⁱ)₅ afford novel heterobimetallic complexes of the type [Al(η²-L)(η²-L*){OGOM(OPrⁱ)_n-1}] (5,M =B, n = 3, L = L^l, L* = L³; <b>6</b>, M =B, n = 3, L = L ², L* = L ⁴; <b>7</b>, M = Ti, n = 4. L = L^l, L* = L³: <b>8</b>, M = Ti, n = 4, L = L², L* = L ⁴; <b>9</b>, M = Nb, n = 5, L = L¹, L* = L³; <b>10</b>, M = Nb, n = 5, L = L², L* = L⁴). All these homo- and heterometallic derivatives have been characterized by elemental analysis, molecular weight measurement s, IR and NMR (¹H, ²⁷Al, and ¹³C) spectral studies and plausible structures have been suggested .