POCKET SEMIQUINONATE COMPLEXES OF COBALT(II), COPPER(II), AND ZINC(II) PREPARED WITH THE HYDROTRIS(CUMENYLMETHYLPYRAZOLYL)BORATE LIGAND

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(cumenyl methyl-pyrazolyl)borate (Tp(Cum,Me)) coligand. Tp(Cum,Me)M(OH), M=Cu a nd Zn with 3,5-di-tert-butylcatechol. Tp Co-Cum,Co-Me(3,5-DBSQ) was pr epared by a reaction between (Tp(Cum,Me))(2)Co and 3,5-DBCat. The iden tity of (Tp(Cum,Me))(2)Co in this reaction was confirmed by a structur e determination [(Tp(Cum,Me))(2)Co: orthorhombic, Pbcn, a=17.7189(4) A ngstrom, b=17.8406(3) Angstrom, c=25.7123(6) Angstrom, V=7964.1(3) Ang strom(3), Z=4, R(F)=0.054]. Intersecting cumenyl substituents of the p yrazolylborate ligand encapsulate the Co(II) ion. Structural character ization on all three members of the Tp(Cum,Me)M(3,5-DBSQ) series has b een carried out. The complexes of Co(II) and Zn(II) are isomorphous an d isostructural [Tp(Cum,Me)Co(3,5-DBSQ): triclinic, P (1) over bar, a= 14.4631(2) Angstrom, b=18.5438(3) Angstrom, c=21.6142(2) Angstrom, alp ha=79.8430(10)degrees, beta=90.0900(10)degrees, gamma=84.9900(10)degre es, V=5683.45(13) Angstrom(3), Z=4, R(F)=0.072; Tp(Cum,Me)Zn(3,5-DBSQ) , triclinic, P (1) over bar, a=14261(3) Angstrom, b=18.760(7) Angstrom , c=21.710-(4) Angstrom, alpha =80.049(12)degrees, <beta<=89.853(8)deg rees, gamma=85.542(12)degrees, V=5703(3) Angstrom(3), Z=4, R(F) = 0.06 4]. Tp(Cum,Me) Cu(3,5-DBSQ) [monoclinic, P2(1)/c, a=19.3081(3) Angstro m, b=13.0291(2) Angstrom, c=21.4783(4) Angstrom, beta=102.8420(10)degr ees, V=5268.1(2) Angstrom(3), Z=4, R(F)=0.071] has a distorted square pyramidal structure, the complexes of Zn and Co have structure that ar e 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 structurall y. Copper(II) and SQ spins of Tp(Cum,Me)Cu(3,5-DBSQ) are located in or thogonal orbitals, and the complex has a S=1 spin state. The charge di stribution in Tp(Cum,Me)Co(3,5-DBSQ) is Co(II)-SQ, rather than the mor e common Co(III)-Cat, due to surprisingly weak donation by the Tp(Cum, Me) nitrogens.