Synthesis and structural characterization of magnesium and cobalt derivatives of the bulky aryl ligand -C6H3-2,6-Mes2

Article abstract of DOI:10.1016/S0022-328X(96)06560-6

The synthesis and structural characterization of the new metal-terphenyl derivatives [BrMC₆H₃-2,6-Mes₂(THF)]₂ (M = Mg (1), Co (2); Mes = -C₆H₂-2,4,6-Me₃) are described. The magnesium derivative 1 was synthesized by reaction of the previously known iodide IC₆H₃-2,6-Mes₂ with activated magnesium. Subsequent treatment of 1 with CoCl₂ affords 2 in moderate yield. Compounds 1 and 2 have very similar dimeric structures, in which two bromides bridge two metals. Each metal is also coordinated to a -C₆H₃-2,6-Mes₂ group and a THF molecule. The metals are thus four-coordinated. The cobalt species 2 is a very unusual example of a stable Co(II) σ-bonded hydrocarbyl. The Co-Co separation of ca. 3.5 A precludes the existence of significant metal-metal bonding. Crystal data at 130K with Μ? Κα (λ = 0.71073 A) radiation: 1, a = 9.432(2), b = 21.973(5), c = 12.558(2)A, β = 94.87(2)°, Z = 2, monoclinic, space group P2₁/c, R = 0.058 for 3006( I > 2σ(I)) data, 2, a = 9.394(2), b = 22.033(7), c = 12.390(3)A, β = 94.99(2)°, Z = 2, monoclinic, space group P2₁/c, R = 0.077 for 2675( I > 2σ(I)) data.