Y. Arai

Crystalline-state reaction of cobaloxime complexes. 17. Requirements for racemization of the bulky dimethoxycarbonylethyl group

Two crystal structures, [(R)-1,2-dimethoxycarbonylethyl]bis(dimethylglyoximato)[(R)-phenylethylamine]cobalt(III) (R-pea) and [(R)-1,2-dimethoxycarbonylethyl]bis(dimethylglyoximato)(1-propylamine)cobalt(III) methanol solvate (pa), have been determined. R-pea: [Co(C 4 H 7 N 2 O 2 ) 2 (C 6 H 9 O 4 )(C 8 H 11 N)], M r =555;5, monoclinic, P2 1 , a= 9.125 (1), b=15.820 (2), c=9.348 (1) A, β= 102.57 (1) o , V=1317.0 (1) A 3 , Z=2, D x = 1.40 g cm -3 , λ(Mo Kα)=0.71069 A, μ=7.32 cm -1 , F(000)=584, T=298 K, R=0.055 and wR=0.049 for 2208 observed reflections. pa: [Co(C 4 H 7 N 2 O 2 ) 2 (C 6 H 9 O 4 )(C 3 H 9 N)].CH 3 OH, M r =525.4, monoclinic, P2 1 , a= 9.803 (3), b=15.554 (3), c=9.267 (3) A, β= 117.24 (2) o , V=1255.4 (1) A 3 , Z=2, D x = 1.39 g cm -3 , λ(Mo Kα)=0.71069 A, μ=7.66 cm -1 , F(000)=556, T=298 K, R=0.070 and wR=0.076 for 1699 observed reflections

[(R)-1,2-Bis(allyloxycarbonyl)ethyl]bis(dimethylglyoximato-N,N')[(R)-1-phenylethylamine]cobalt(III)

A new bis(dimethylglyoximato)cobalt(III) complex with a bulky chiral alkyl group bonded to the Co atom has been prepared, [Co(C4H7N2O2)2(C10H13O4)(C8H11N)]. The crystal was irradiated with a xenon lamp. Racemization of the crystalline state was not observed for the crystal since the reaction cavity for the chiral alkyl group appears to be too small.

Structure of [(R)‐1,2‐dimethoxycarbonylethyl]bis(dimethylglyoximato)[(S)‐1‐phenylethylamine]cobalt(III)

C 22 H 34 CoN 5 O 8 cristallise dans P3 2 avec a=14,942, c=10,174 A, Z=3; affinement jusqua R=0,041. La structure ne change pas apres exposition aux rayons X a 298 K. Le groupement 1,2-dimethoxycarbonylethyl adopte une conformation de forme L

Multi-Stage Crystalline State Racemization of a Bulky Chiral Group

Abstract A chiral dimethoxycarbonylethyl group in a cobaloxime complex with pyridine as an axial base ligand revealed crystalline-state racemization by X-ray exposure or visible light, whereas those of complexes with (S)- and (R)-phenylethylamines and propylamine showed no change. Such differences can be explained by the size of the reaction cavity for the dimethoqcarbonylethyl group and the packing mode of the groups in each crystal.

[(R)-1,2-Diethoxycarbonylethyl]bis(dimethylglyoximato)(methyldiphenylphosphine)cobalt(III)

The crystal structure of the title compound, [Co(C 4 H 7 N 2 O 2 ) 2 (C 8 H 13 O 4 )(C 13 H 13 P)], has been determined in order to examine whether or not the chiral 1,2-diethoxycarbonylethyl group is racemized on exposure to either visible light or X-rays with retention of the single-crystal form. Although the reaction cavity of the chiral group is considerably large, the chiral group is isolated from the other chiral groups in the structure. The cooperative motion between the chiral groups necessary for the racemization of bulky groups may be impossible in such an isolated environment

[(S)-1-Carbamoylethyl]bis­(dimethyl­glyoximato-κ2N,N′)[(S)-1-phenyl­ethyl­amine]cobalt(III) and bis­(dimethylglyoximato-κ2N,N′)[(R)-1-(N-methyl­carbamoyl)ethyl][(R)-1-phenyl­ethyl­amine]cobalt(III) monohydrate

The title complexes, [Co(C3H6NO)(C4H7N2O2)2(C8H11N)] and [Co(C4H8NO)(C4H7N2O2)2(C8H11N)]·H2O, were resolved from [(RS)-1-carbamoylethyl]bisxad(dimethylxadglyoximxadato)[(S)-1-phenylxadethylxadamine]cobalt(III) and bisxad(dixadmethylxadglyoximato)[(RS)-1-(N-methylxadcarbamoyl)xadethyl][(R)-1-phenylxadethylxadamine]cobalt(III), respectively, and their crystal structures were determined in order to reveal the absolute configuration of the major enantiomer produced in the photoisomerization of each series of 2-carbamoylethyl and 2-(N-methylxadcarbamoyl)ethyl cobaloxime complexes.

Bis(dimethylglyoximato-N, N')[methyl(R)-ethanoato-C2][tris(2-cyanoethyl)-phosphine-P]cobalt(III)

The title compound, [Co(C4H7N2O2)2(C4H7O2)(C9H12N3P)], has been analyzed by X-ray diffraction to correlate the structure with the reactivity of the photoracemization on exposure to visible light. Although the crystal decomposed during the racemization, the size of the reaction cavity for the 1-methoxycarbonylethyl group explains the high reactivity.