Beiträge zur chemie organometallischer metallacyclischer nebengruppenmetallverbindungen: X. Synthese, NMR-spektroskopische und DTA-untersuchungen der ersten homoleptischen metallacyclischen “at-komplexe” des typs [LiL x] 2[formula omitted]HR) 2 (L = ein- bzw. zweizähliger ligand; R H, CH 3) - molekülstruktur von [Li(TMEDA)] 2[formula omitted]H 2) 2

Abstract

The compounds [Li(Et 2O) 2] 2 Zn(CH 2CH 2CH 2C H 2) 2 1, [Li 2(Et 2O) 3] Zn(CH(CH 3) CH 2CH 2C H 2) 2 7, [Li(Et 2O) 2] 2 Zn(CH(CH 3)CH 2CH 2C H(CH 3)) 2 10, [Li(TMEDA)] 2 Zn(CH 2CH(CH 3)CH 2C H 2) 2 13 and [Li 2(Et 2O) 2.3] Zn(CH 2CH(CH 3)CH(CH 3)C H 2) 2 14 were synthesized by treatment of ZnCl 2 with the dilithium compounds LiCH 2CH 2CH 2CH 2Li, LiCH(CH 3)-CH 2CH 2CH 2Li, LiCH(CH 3)CH 2CH 2CH(CH 3)Li, LiCH 2CH(CH 3)CH 2CH 2Li or LiCH 2CH(CH 3)CH(CH 3)CH 2Li in diethyl ether. Some of these complexes ( 7, 10) were also readily obtained by a one-pot reaction of the corresponding dichloralkanes, ZnCl 2 and lithium. By substituting other n-donors for the diethyl ether in the compounds 1, 7, 10 and 14 derivatives of the composition [LiL x ] 2 Zn(CHRCHRCHRC HR) 2 ( L = uni- or bidentate ligand; R  H, CH 3) were obtained. The complexes were characterized by elemental and DTA analysis, many of them by 1H and 13C NMR spectroscopy, some of the CH 3 substituted compounds also by DEPT- and two-dimensional H,C-correlated 200 MHZ-NMR spectra. The results of the 13C NMR investigations showed the β-CH 3 substituted zinc complexes to be mixtures of isomers. The crystal structure of [Li(TMEDA)] 2 Zn(CH 2CH 2CH 2C H 2) 2 3 was determined by an X-ray diffraction study. The crystal data and the final R values are as follows: crystal system monoclinic, space group P2 1/ c (No. 14) with cell parameters a = 18.826(2) Å, b = 13.486(3) Å, c = 20.367(2) Å, β = 96.12(1) °, Z = 8, R = 0.061, R w = 0.077. The average distance LiZn (2.42 Å) of the tetrahedral complex 3 is comparable with the sum of the covalence radii of these two elements (2.48 Å).