title: Synthesis and characterization of low-coordinate divalent aryl transition-metal halide analogues of grignard reagents: precursors for reduction to metal-metal-bonded complexes.
abstract: The synthesis and characterization of the series of divalent first-row aryl transition-metal(II) halide compounds [Cr(mu-Cl)Ar']2 (1) and (Li(OEt2)Ar'MI2]2 (M=Mn (2), Fe (3), and Co (4); Ar'=C6H3-2,6-(C6H3-2,6-iPr2)2) are described. 1-4 were prepared by the addition of one equiv of Ar'Li to the respective transition-metal dihalides. They were characterized by UV-vis spectroscopy, magnetic measurements, and by X-ray crystallography. In dimeric 1, each chromium center has quasi-four-coordinate, square-planar geometry, in which the metal is terminally bound to a terphenyl ligand through the ipso carbon of the central ring and to two bridging chloride ligands. There is a further interaction between chromium and an ipso carbon from one of the flanking -C6H3-2,6iPr2 rings. In contrast, for the iodo derivatives 2-4, LiI is not eliminated upon addition of LiAr' to MI2. Instead, the diethyl ether solvated adducts, [Li(OEt2)Ar'MI2]2 (M=Mn (2), Fe (3), or Co (4)) were isolated. These possess a distorted cubane Li2M2I4 core, in which the lithiums are bound to an ether and the transition metals are bound to a terphenyl group. Magnetic measurements between 2 and 300 K reveal the expected weak antiferromagnetic exchange coupling in each of the complexes.
authors.affiliation: Department of Chemistry, One Shields Avenue, University of California, Davis, California 95616, USA.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Sutton
authors.forename: Tailuan
authors.initials: T
authors.lastname: Ngyuen
authors.forename: James C
authors.initials: JC
authors.lastname: Fettinger
authors.forename: Marilyn M
authors.initials: MM
authors.lastname: Olmstead
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Long
authors.forename: Philip P
authors.initials: PP
authors.lastname: Power