SYNTHESIS, STRUCTURE AND MAGNETIC-PROPERTIES OF MONONUCLEAR AND DINUCLEAR CHROMIUM(III) COMPLEXES WITH TETRAHYDROSALEN AND SUBSTITUTED TETRAHYDROSALEN DERIVATIVES AS LIGANDS - CRYSTAL-STRUCTURE OF A PHENOXO-BRIDGED DICHROMIUM(III) COMPLEX

Two dinuclear chromium(III) complexes and one mononuclear chromium(III ) complex have been synthesized by the reaction of CrCl(3)(.)6H(2)O or trans-[Cr(py)(4)Cl-2]I (in 2-methoxyethanol) with tetrahydrosalen and substituted tetrahydrosalen derivatives L(1), L(3) and L(7) (in the f ollowing L(i) denotes the anions of H(2)L(1), H(2)L(3) or HL(7)). H(2) L(1) = N,N'-bis(2-hydroxybenzyl)-1,2-ethanediamine, -hydroxybenzyl)-tr ans-(S,S)-1,2-cyclohexanediamine and HL(7)=N-(3-tert-butyl-2-hydroxy-5 -methylbenzyl)-N' -(2-pyridyl)ethyl)-1,1-dimethyl-1,2-ethanediamine. T wo new complexes with the stoichiometric formulae [CrLCl](2) (L=L(1) a nd L(3)) and one new complex with the stoichiometric formula [CrLCl(2) ] (L=L(7)) were obtained. The crystal structure of [CrL(1)Cl](2) has b een determined. The crystal system Is orthorhombic, the lattice consta nts are a=8.205(1), b=15.631(2), c=24.426(1) Angstrom, the volume of t he unit cell is 3132.95(56) Angstrom(3). The space group is Pbca. The refinement of 207 variables includes 2146 of the 3264 independent refl ections. The final residual is 3.94%. The dinuclear molecule consists of two slightly distorted octahedrally cis-coordinated chromium centre s bound together by two phenoxo bridges. The Cr-O-Cr angle is 100.84(9 )degrees and the Cr-O(bridge) distances are 2.022(2) and 2.024(2) Angs trom, respectively. The configuration of the dinuclear molecule is Del ta,Lambda, where Delta and Lambda refer to the configuration of the tw o N,O chelates of the salen ligand. The Cr(1)-Cr(1) distance is 3.118 Angstrom. The two complexes [CrL(1)Cl](2) and [CrL(3)Cl](2) behave as typical antiferromagnetically coupled dinuclear compounds with J-valu es of 17.1 and 16.7(1) cm(-1), respectively. The EPR spectrum of [CrL( 3)Cl](2) in a frozen glass (N'-methylformamide) was measured at 80 K a nd is a typical spectrum from the quintet state which emerges as a res ult of the antiferromagnetic coupling of the two chromium(III) ions in the dinuclear complex. The spectrum was simulated using the parameter s g=1.98, J=16.7 cm(-1), D-e=0.061 cm(-1) and E(e)=0.0052 cm(-1). The magnetic susceptibility data of the complex [CrL(7)Cl(2)] shows the ex pected behaviour of a mononuclear complex. This was confirmed by the E PR spectrum of the compound dissolved in N-methylformamide which is ty pical for a mononuclear complex with a considerable zero-held splittin g.