The synthesis and structure of some, rac–trans-, meso–trans- and (S,S)-trans- Co(III) complexes with Me6-[14]-diene(5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene)

Abstract

The reaction of cis-[Co(CO3)(Me6-[14]-diene)]ClO4 with S-(+)-mandelic acid gives first (S,S)-trans-[Co(S-mandelato)2(Me6-[14]-diene)]ClO4·2H2O (1) and then (R,S)-trans-[Co(S-mandelato)2(Me6-[14]-diene)]ClO4·H2O (2). With HCl, the cis-carbonato gives first rac–trans-[CoCl2(Me6-[14]-diene)]ClO4 (3) and then increasing amounts of meso–trans-[CoCl2(Me6-[14]-diene)]ClO4 (4). The rac–trans-perchlorate (3) can be isomerised partially to the meso-form (4) in refluxing methanol. Treatment of 1 with HCl/HClO4 gives (+)-(S,S)-trans-[CoCl2(Me6-[14]-diene)]ClO4 which racemises in methanol to give a rac-/meso-mixture. Attempts to resolve rac–trans-[CoCl2(Me6-[14]-diene)]+ directly with the antimonyl(III) tartrate anion were not successful, but work-up of the solution with HCl gave X-ray quality crystals of rac–trans-[CoCl2(Me6-[14]-diene)]2Sb2Cl8 (5) containing dimers of the seesaw shaped SbCl4− anion. trans-[CoBr2(Me6-[14]-diene)]ClO4 reacts with dilute aqueous ammonia to give trans-[Co(OH)(Me6-[14]-diene)(NH3)](ClO4)2. Acidification of this allows the isolation of synrac–trans-[Co(Me6-[14]-diene)(NH3)(OH2)](ClO4)3, which slowly isomerises in acidic solution [kisom=2.92×10−5 s−1 at 25°C] to the meso-form. Two isomers of [CoCl(Me6-[14]-dien)(NH3)]2+ have also been isolated, the synrac–trans-perchlorate and the meso–trans-tetrachlorozincate (6) and their aquation rates (chloride release) have been measured. The crystal structures of compounds 1–6 have been determined.