Synthesis and characterization of lithium, aluminium and zinc complexes supported by pyrazolyl-based N,N′-chelate ligands

A series of lithium, aluminium and zinc complexes bearing [3,5-R2C3HN2CHC(R-1)N(R-2)](-) ligands were synthesized and characterized. Treatment of 1-(Me3SiCH2)-3,5-R2C3HN2 (R = Me, Bu-t) with LiBun and then (BuCN)-C-t afforded [Li{N(SiMe3)C(Bu-t)CHN2C3HR2-3,5}](2) (R = Me, 2a; R = Bu-t, 2b). Reaction of both 2a and 2b with ZnCl2 gave zinc complexes [Zn(Cl){N(SiMe3)C(Bu-t)CHN2C3HR2-3,5}](2) (R = Me, 3a; R = Bu-t, 3b). Treatment of o-RC6H4NHC(Ph)CHN2C3HMe2-3,5 (R = OPri, 5a; R = Me, 5b) with LiBun yielded lithium complexes similar to 2a or 2b, [Li{N(o-RC6H4)C(Ph)CHN2C3HMe2-3,5}] (R = OPri, 6a; R = Me, 6b). Reaction of 6b with ZnCl2 generated zinc complexes [Zn(Cl){N(o-MeC6H4)C(Ph)CHN2C3HMe2-3,5}] (7), and with AlCl3 gave [Al(Cl-2){N(o-MeC6H4)C(Ph)CHN2C3HMe2-3,5}] (8). Reaction of 5a with ZnEt2 produced [Zn{N(o-(PrC6H4)-C-i)C(Ph)CHN2C3HMe2-3,5}(2)] (9). Reaction of 5a and 5b with AlR'(3) (R' = Me, Et) afforded aluminium complexes [Al(R'(2)){N(o-RC6H4)C(Ph)CHN2C3HMe2-3,5}] (R = OPri, R' = Me, 10a; R= Me, R' = Me, 10b; R = OPri, R' = Et, 10c; R = Me, R' = Et, 10d). A trace of species [Al(Et-2){N(o-MeC6H4)C(Ph)(Et)CH2N2C3HMe2-3,5}] (11) was also isolated from the reaction products of 5b and AlEt3. All of new compounds were characterized by H-1 and C-13 NMR spectroscopy and elemental analyses. Structures of complexes 2a, 8, 10a, 10d and 11 were additionally characterized by single-crystal X-ray diffraction techniques.