Di- and tri-valent chlorochromium complexes bearing hydrotris(3,5-diisopropylpyrazolyl)borato ligand (Tp(iPr2)), Tp(iPr2)CrCl(n)(L) (n=1, 2) and [Tp(iPr2)Cr(mu-Cl)](2): flexible coordination behavior of the Tp(iPr2) ligand and reduction features of C

摘要

Divalent chlorochromium complexes bearing the Tp(iPr2) ligand [hydrotris(3,5-diisopropylpyrazolyl)borato], Tp(iPr2)Cr(II)Cl(L) [L = 3,5-diisopropylpyrazole (1a), py (1b), bipy (2)] and Tp(iPr2)Cr(II)(mu-Cl](2) (3), were prepared by treatment of CrCl2 with a Tp(iPr2) salt in the presence (1,2)/absence (3) of a donor (L). Reaction of I with benzyl chloride results in quantitative conversion to the corresponding trivalent dichlorochromium species, Tp(iPr2)Cr(III)-Cl-2(L) (6), while reaction with CH2Cl2 gives the methylene-inserted product, Tp(iPr2)Cr(III)Cl(CH2-L) 7, via a carbene intermediate, which is supported by cyclopropanation of styrene with CH2Cl2 in the presence of 3. The Cr(II) complex 1b induces reductive coupling of benzaldehyde to give a 3,4-diphenyl-2,5-dioxachromacyclopent-3-ene, Tp(iPr2)Cr[kappa(2)-O-C(Ph)=C(Ph)-O] 8. Steric tuning effects of the Tp(iPr2) ligand leads to a variety of coordination geometries including five-coordinate square-pyramidal and trigonal-bipyramidal structures and a six-coordinate octahedral structure as revealed by crystallographic characterization. [References: 78]