Syntheses and X-ray crystal structures of zinc complexes with an amido-diamine ligand Bing Luo, Benjamin E. Kucera, Wayne L. Gladfelter * Department of Chemistry, University of Minnesota, 207 Pleasant Street, SE, Minneapolis, MN 55455, United States Received 12 April 2005; accepted 29 June 2005 Available online 18 August 2005 Dedicated to Malcolm Chrisholm on the occasion of his 60th birthday Abstract The synthesis and characterization of complexes with a tridentate amido-diamine ligand –N(CH 2 CH 2 NMe 2 ) 2 , [ClZnN(CH 2 CH 2 NMe 2 ) 2 ] 2 (1), [EtZnN(CH 2 CH 2 NMe 2 ) 2 ] 2 (2), {Zn[N(CH 2 CH 2 NMe 2 ) 2 ] 2 } 2 (3) and [ i Bu 2 NZnN(CH 2 CH 2 NMe 2 ) 2 ] 2 (4), are described. Compounds 1 (57% yield) and 2 (49% yield) were obtained from the reactions of ZnCl 2 with 1 equiv. of LiN(CH 2 CH 2 NMe 2 ) 2 and ZnEt 2 with excess HN(CH 2 CH 2 NMe 2 ) 2 , respectively. Compounds 3 (52% yield) and 4 (75% yield) were isolated from the reactions of [Zn(N i Bu 2 ) 2 ] 2 with HN(CH 2 CH 2 NMe 2 ) 2 in 1:4 and 1:2 molar ratios, respectively. Mass spectral data and NMR analyses suggested that all four compounds were dimeric. The solid-state structures of compounds 2 and 3 were deter- mined via X-ray crystallography. Both compounds were centrosymmetric containing a four-membered Zn 2 N 2 ring with bridging amido ligands. In both structures, one NMe 2 group in each bridging ligand bonded to a Zn center forming a five-membered ring. The ethyl groups in 2 and the second –N(CH 2 CH 2 NMe 2 ) 2 ligand in 3 occupied the terminal positions. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Zinc; Tridentate; Amide; Amido; Structure; Dimer 1. Introduction Zinc coordination chemistry, involving a variety of nitrogen ligands, is of fundamental importance in chem- istry, biology and materials science [1]. Structurally characterized diamido zinc compounds, Zn(NR 2 ) 2 , where R is a bulky alkyl, silyl or aryl group, are typically monomeric with dicoordinate zinc [2–7] or dimeric with tricoordinate zinc atoms [4,6,8–10] (Scheme 1, i and ii). Compounds with less sterically demanding ligands, such as bis(dimethylamido)zinc [11] and bis(diethylamido)- zinc [12], are polymeric. The coordinative saturation of zinc amido complexes can also be achieved with addi- tion of Lewis base ligands. Examples include monomeric Zn(NPh 2 ) 2 (THF) 2 [8] and dimeric [MeN(SiMe 2 NEt) 2 - Zn(pyridine)] 2 [13]. For less bulky bidentate amido- amine ligands, only hydrido and alkyl zinc derivatives are known. Examples are [HZnNMe(CH 2 ) 2 NMe 2 ] 2 [14] and [RZnNMe(CH 2 ) n NMe 2 ] 2 (n = 2 or 3 and R = Me or Et) [15] (Scheme 1, iii). We are interested in preparing the volatile zinc com- plexes for the chemical vapor deposition of zinc-contain- ing films. This led us to investigate the chemistry of a tridentate amido-diamine ligand, –N(CH 2 CH 2 NMe 2 ) 2 . The lithium salt of [N(CH 2 CH 2 NMe 2 ) 2 ]  has been re- ported [16,17], and a volatile five-coordinate gallium dihydride has been characterized [18]. In this paper, we report the synthesis and characterization of several zinc complexes bearing a –N(CH 2 CH 2 NMe 2 ) 2 ligand. 0277-5387/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2005.06.041 * Corresponding author. Tel.: +1 612 624 4391; fax: +1 612 626 8659. E-mail address: gladfelt@chem.umn.edu (W.L. Gladfelter). www.elsevier.com/locate/poly Polyhedron 25 (2006) 279–285