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Pocket Semiquinonate Complexes of Cobalt(II), Copper(II), and Zinc(II) Prepared with the Hydrotris(cumenylmethylpyrazolyl)borate Ligand

1997; American Chemical Society; Volume: 36; Issue: 21 Linguagem: Inglês

10.1021/ic970244t

1520-510X

Michael Ruf, B.C. Noll, Markus D. Groner, G.T. Yee, Cortlandt G. Pierpont,

Lanthanide and Transition Metal Complexes

3,5-Di-tert-butyl-1,2-semiquinonate (3,5-DBSQ) complexes of Co(II), Cu(II), and Zn(II) have been prepared that contain the hydrotris(cumenylmethyl-pyrazolyl)borate (Tp(Cum,Me)) coligand. Tp(Cum,Me)Zn(3,5-DBSQ) and Tp(Cum,Me)Cu(3,5-DBSQ) were prepared by treating the parent hydroxide, Tp(Cum,Me)M(OH), M = Cu and Zn, with 3,5-di-tert-butylcatechol. Tp(Cum,Me)Co(3,5-DBSQ) was prepared by a reaction between (Tp(Cum,Me))(2)Co and 3,5-DBCat. The identity of (Tp(Cum,Me))(2)Co in this reaction was confirmed by a structure determination [(Tp(Cum,Me))(2)Co: orthorhombic, Pbcn, a = 17.7189(4) Å, b = 17.4806(3) Å, c = 25.7123(6) Å, V = 7964.1(3) Å(3), Z = 4, R(F) = 0.054]. Intersecting cumenyl substituents of the pyrazolylborate ligand encapsulate the Co(II) ion. Structural characterization on all three members of the Tp(Cum,Me)M(3,5-DBSQ) series has been carried out. The complexes of Co(II) and Zn(II) are isomorphous and isostructural [Tp(Cum,Me)Co(3,5-DBSQ): triclinic, P&onemacr;, a = 14.4631(2) Å, b = 18.5438(3) Å, c = 21.6142(2) Å, alpha = 79.8430(10) degrees, beta = 90.0900(10) degrees, gamma = 84.9900(10) degrees, V = 5683.45(13) Å(3), Z = 4, R(F) = 0.072; Tp(Cum,Me)Zn(3,5-DBSQ), triclinic, P&onemacr;, a = 14.261(3) Å, b = 18.760(7) Å, c = 21.710(4) Å, alpha = 80.049(12) degrees, beta = 89.853(8) degrees, gamma = 85.542(12) degrees, V = 5703(3) Å(3), Z = 4, R(F) = 0.064]. Tp(Cum,Me)Cu(3,5-DBSQ) [monoclinic, P2(1)/c, a = 19.3081(3) Å, b = 13.0291(2) Å, c = 21.4783(4) Å, beta = 102.8420(10) degrees, V = 5268.1(2) Å(3), Z = 4, R(F) = 0.071] has a distorted square pyramidal structure, the complexes of Zn and Co have structures that are closer to a trigonal bipyramid. Parent catecholate complexes of all three metals are unusually stable in air but undergo slow oxidation in solution to give the semiquinonate products characterized structurally. Copper(II) and SQ spins of Tp(Cum,Me)Cu(3,5-DBSQ) are located in orthogonal orbitals, and the complex has a S = 1 spin state. The charge distribution in Tp(Cum,Me)Co(3,5-DBSQ) is Co(II)-SQ, rather than the more common Co(III)-Cat, due to surprisingly weak donation by the Tp(Cum,Me) nitrogens.