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RESEARCH PRODUCT

Adducts of 1,4-diazabutadienes with group IIB metal halides

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Abstract The reactions of 1,4-diazabutadienes (or α-diimines) RNC(R′)C(R″)NR, DAB, (R = p -C 6 H 4 OMe, R′ = R″ = H, DAB I ; R = p -C 6 H 4 OMe,R′ = H, R″ = Me, DAB II ; R = p -C 6 H 4 OMe, R′= R″ = Me; DAB III ; R = CMe 3 , R′ = R″ = H, DAB IV ) with MX 2 M = Zn, Cd, Hg; X = CI, Br) yield in general 1/1 adducts. These species are assigned a monomeric configuration with a σ,σ′-N,N′, chelating DAB ligand for M = Zn, Hg, whereas the CdCl 2 adducts have polymeric structures with terminal and/or bridging chlorides. In the reactions of CdCl 2 with DAB I or DAB IV polymeric species [(CdCl 2 ) 2 (DAB)] x are obtained in which all chlorides are bridging. Spectrophotometric dissociation equilibrium constants have been determined by titration methods in 1,2-dichloroethane for some Zn and Hg 1/1 adducts. The stability constants depend markedly on the substituents on the imine C and N atoms. When R = CMe 3 (DAB) IV no dissociation is detected, whereas with R = p -C 6 H 4 OMe the stability constants increase in the order: DAB I II ⩽ DAB III which is apparently the order of increasing σ-donor ability of the α-diimine ligands. The [ZnCl 2 (DAB I )] complex is ca. 30 times more stable than its Hg analogue. Computational details of the equilibrium measurements are also discussed.