Synthesis and some octahedral complexes of a chiral triaza macrocycle

Geometrical isomerism in octahedral complexes arising from the presence of a fused ring on a triaza macrocycle

“…† Previously, only the anti arrangement has been characterised, found in the cobalt() complex, so exemplification of this potential form of isomerism was not forthcoming. 2 Now, we present evidence from X-ray structural studies of chromium() and nickel() complexes that both the syn and anti dispositions can form and are observed for these ions respectively. The preferences of octahedral metal ions for these forms have been probed via a molecular mechanics analysis.…”

“…the well-studied Richman-Atkins procedure, 16-20 as described previously. 2 Syntheses of octahedral metal complexes have earlier been performed successfully with either racemic, RR-or SS-trans-L 1 , with products differing in chiroptical properties only; 2 here, the RR-trans-L 1 has been employed exclusively.…”

“…13 Recently, we reported the synthesis and some coordination chemistry of the chiral fused-ring cyclic triamine L 1 , which can bind facially to octahedral metal ions. 2 The simplest and most studied example of a cyclic polyamine capable of coordinating facially to an octahedral complex is the triazamacrocycle 1,4,7-triazacyclononane (tacn, 1 L 2 ). The coordination chemistry of this molecule has been comprehensively investigated, especially by Wieghardt and coworkers.…”

Recent advances in catalytic asymmetric epoxidation using the environmentally benign oxidant hydrogen peroxide and its derivatives

“…27 The group also reported the first successful application of 8 in the epoxidation of alkenes in the peer reviewed literature although yields and ees were markedly inferior to those previously claimed by Beller for a number of substrates in earlier patents. 28 A closely related structure 9 was prepared by Watkinson et al 29,30 and Golding et al 31 although its catalytic properties in the epoxidation of alkenes were never exploited.…”

The application of manganese complexes of ligands derived from 1,4,7-triazacyclononane in oxidative catalysis

“…31 The first report of 36b appeared in an extensive study of coordination chemistry in octahedral complexes of cobalt(III), chromium(III), iron(III) and nickel(II) containing two facially coordinated ligands. 32 Our initial efforts in this area were frustrated by the difficulties associated with the preparation of 36b, 33 however, as part of these investigations we also happened to prepare a closely related azaoxa-analogue. Following these reports three groups concurrently reported the synthesis of a number of C 2 -symmetric analogues derived from chiral pool amino acids, 37, 34-36 but in only one case were applications in asymmetric epoxidation reported.…”