ChemInform Abstract: Cobalt(III) Complexes with N‐Methylethane‐1,2‐diamine (meen). Crystal Structures of the Stable Isomers of (Co(meen)3)3+ and (Co(meen)2(en))3+

Abstract

Abstract The X-ray crystal structures of two geometric isomers-diastereoisomers of [Co(meen)3]3+, designated A and C, and one isomer of [Co(meen)2(en)]3+, designated F, are reported (meen=N-methylethane-1,2-diamine). A, C and F (as racemates) were isolated as their bromide salts and crystallized as dimono-, and mono-hydrates respectively. A crystallizes in the triclinic space group P 1 with unit cell dimensions a=8.231(2), b=8.682(1) and c=14.247(2) A, α=96.84(1), β=97.16(2) and γ=99.62(2)°, and Z=2. C crystallizes in the orthorhombic space group Pna21 (implying spontaneous resolution) with a=12.758(3), b=11.236(1) and c=13.19(1) A, and Z=4. Complex F is monoclinic, I2/a, with a=12.626(5), b=22.977(5) and c=12.619(6) A, β=97.84(4)°, and Z=8. The structures were solved by direct methods and each was refined by a full-matrix least-squares procedure. Final refinement details for A (those for C and F follow in parentheses): R 0.044 (0.040; 0.038), Rw 0.046 (0.041; 0.041) for 2487 (1318; 1693) reflections with I⩾2.5σ(I). The complex cations feature octahedrally coordinated Co(III) centres, and they are involved in complicated hydrogen bonding networks with the bromide anions and water molecules in the crystal lattices. The stereochemistries of the complex cations are (one enantiomer specified only) A: Λ-mer-[Co(meen)3]3+-RRR*-λδδ*; C: Λ-mer-[Co(meen)3]3+-RSR*-δλδ*; F: Λ-trans-CH3, cis-NH2-[Co(meen)2(en)] 3+-RR-δδδ. Equatorial methyl dispositions and lel ring geometries predominate, although A has one ring which is ob and which also has the methyl axial, and C has one ob ring.