Methyl-Bridged Transition Metal Complexes (M = Cr−Fe) Supported by Bulky Terphenyl Ligands

The synthesis and characterization of a series of divalent terphenyl transition metal methyl complexes {ArM(μ-Me)}2 (M = Cr (1), Ar = C6H-2,6-(C6H2-2,4,6-iPr3)2-3,5-iPr2, abbreviated as 3,5-iPr2-Ar*; M = Mn (2), Fe (3), Ar = C6H3-2,6-(C6H2-2,4,6-iPr3)2, abbreviated as Ar*) as well as a phenyl-bridged iron complex {Ar*Fe(μ-Ph)}2 (4) are described. Complexes 1−4 were prepared by reaction of the corresponding terphenyl metal halide with LiMe or LiPh and have dimeric structures, in which three-coordinate metals are bridged by methyl or phenyl groups. Each chromium atom in 1 features a further interaction with the ipso-carbon of the flanking aryl ring; while the manganese and iron atoms in 2 and 3 have distorted trigonal-planar geometry. Complexes 1−4 are rare examples of low-coordinate transition metal complexes of methyl or phenyl groups, and they were characterized by X-ray crystallography, NMR, and UV−vis spectroscopy, elemental analysis, and magnetic measurements.