NEW HETEROMETALLIC AND HOMOMETALLIC DIHYDROXO-BRIDGED DINUCLEAR COMPLEXES OF COBALT(III) AND CHROMIUM(III) - SYNTHESIS, SPECTROSCOPY AND CRYSTAL-STRUCTURES

Sixteen new unsymmetrical hetero- and home-metallic dinuclear complexe s [(nta)Cr(mu-OH)(2)ML(4)]Cl . nH(2)O [M = Co-III or Cr-III; L(4) = (N H3)(4), (en)(2), (tn)(2), {(R,R)chxn)(2), (trien), (amp)(2), (bipy)(2) or (phen)(2): nta = nitrilotriacetate, en = ethane-1,2-diamine, chxn = trans-cyclohexane-1,2-diamine, tn = propane-1,3-diamine, amp = 2-ami nomethylpyridine, trien = triethylenetetramine, bipy = 2,2'-bipyridine and phen = 1,10-phenanthroline] were synthesized and characterized by elemental analysis. UV/VIS absorption, circular dichroism and H-2 NMR spectra, acid strengths of bridging hydroxide, magnetic properties an d crystal structures. The crystals of [(nta)Cr mu-OH)(2)M(tn)(2)]Cl . 1.5H(2)O (M = Co or Cr) are isomorphous and belong to the monoclinic s ystem. space group C2/c. Z = 8. with a = 16.384(2), b = 14.660(2), c = 18.874(2) Angstrom, beta = 110.77(1)degrees and a = 16.465(3). b = 14 .727(2), c = 19.057(2) Angstrom, beta = 110.28(1) for M = Co and Cr re spectively. The crystal structure of [(nta)Cr(mu-OH)(2)Cr(phen)(2)]Cl . 7H(2)O was found to be triclinic with space group P1, a = 15.79(1), b = 18.04(1). c = 12.77(1) Angstrom, alpha = 96.39(8)degrees beta = 10 2.23(7), gamma = 102.83(7)degrees and Z = 4. The structural parameters of the bridging moiety around each metal ion were almost the same as in the corresponding symmetrical dinuclear species. The(2)H NM R spect ra of [([H-2(6)]nta)Cr(mu-OH)(2)ML(4)](+) reflected the stereochemistr y of the nta chelate rings and the M-N(of L(4)) bond properties.