Optically active chromium(III) complexes VIII. Chiroptical and epimeric forms of chloro(1,2-diaminoethane) (1,4,8-triazaoctane)chromium(III) complexes and the structural characterization of some pentachloroantimonate(III) salts

Abstract

Racemic- exo-mer-[CrCl(en)(2,3-tri)]ZnCl 4 has been resolved using potassium antimonyl tartrate. The less soluble {−} 447- exo-mer-[CrCl(en)(2,3-tri)][Sb 2(tart) 2]·4H 2O (orthorhombic, P2 12 12 1, a = 12.800(3), b = 12.881(3), c = 16.712(4) A ̊ , V = 2755.4(11) A ̊ 3 , Z = 4) is shown by single crystal X-ray analysis to have the ( R)-configuration at the coordinated sec-NH center. Addition of HCl to the mother liquor results in the isolation of rac-exo-mer-[CrCl(en)(2,3-tri)]SbCl 5 (orthorhombic, Pbca, a = 14.055(3), b = 10.472(2), c = 26.510(5) A ̊ , V = 3901.8(13), Z = 8 ) and further addition of ZnCl 2 allows the isolation of (+)-( S)- exo-mer-[CrCl(en)(2,3-tri)]ZnCl 4. Exo-mer-[CrCl(Me 2tn)(3,3-tri)]SbCl 5·H 2O·0.5HCl (monoclinic, Cc, a = 16.002(2), b = 11.627(5), c = 27.571(6) A ̊ , β = 99.79(2)°, V = 5055(3) A ̊ 3, Z = 8 ) has also been obtained from the crude chloride salt using potassium antimonyl tartrate and 6M HCl. Both SbCl 5 2− salts contain isolated SbCl 5 2− anionic units. Rac-exo-mer-[CrCl(en)(2,4-tri)ZnCl 4 has been converted into rac-endo-mer-[CrCl(en)(2,3-tri)ZnCl 4 (monoclinic, P2 1/c, a = 11.682(2), b = 13.915(2), c = 10.809(2) A ̊ , β = 93.31(2)°, V = 1781.2(5) A ̊ 3, Z = 4 ) by base hydrolysis. Treatment of (−)-( R)- exo-mer-[CrCl(en)(2,3-tri)]ZnCl 4 with NH 3(liq.) and sodium amide results in the formation of {−} 450-( R)- exo-mer-[Cr(NH 3)(en)S(2,3-tri)] 3+ (isolated as the Hg 2Cl 7 3− salt) but with considerable loss of optical purity. We have also confirmed the orientation of the chelated aminomethylpyridine (ampy) ligand in exo-mer-[CrCl(ampy)(2,3-tri)HgCl 4·H 2O (monoclinic, P2 1/c, a = 11.867(5), b = 10.2780(10), c = 17.318(5) A ̊ 3, Z = 4 ) has having the −CH 2NH 2 arm trans to the coordinated chloro ligand.