82665-67-6Relevant academic research and scientific papers
Synthesis, crystal and molecular structure, and chemistry of (μ-trimethylene)bis(η-cyclopentadienyl)bis(aμ-carbonyl)dicobalt, a five-membered dlcobaltacycle
Theopold, Klaus H.,Bergman, Robert G.
, p. 1571 - 1579 (2008/10/08)
Treatment of Na[CpCo(CO)]2 with l,n-dihaloalkanes leads in certain cases to double alkylation, giving dinuclear metallacycles containing two adjacent cobalt atoms. This paper reports the synthesis and study of several such systems and an in-depth investigation of the five-membered dimetallacycle 1 prepared from 1,3-diiodopropane. The molecular structure of 1 was determined by X-ray diffraction, using 1016 reflections (R = 2.47). The crystals were orthorhombic (space group Fdd2), with unit-cell parameters a = 16.7983 ?, b = 45.576 ?, c = 6.9565 ?. The complex has an open envelope ring structure, with a dihedral angle of 32.9°; the Co-Co bond distance is 2.413 ?. Thermolysis of 1 (80-100°) gives cyclopropane and propene. Reaction of 1 with CO or phosphines (L) occurs at lower temperature, leading to a product distribution which is dependent upon the concentration of L. At low [L], the reaction leads to cyclopropane mixed with a small amount of propene and CpCo(L)(CO). High [L] produces CpCo(L)(CO) and mononuclear metallacyclopentanones 6, 7, or 8 depending on the entering ligand. Thermolysis of the metallacyclopentanones leads again to cyclopropane and propene rather than to cyclobutanone. Kinetic and isotope labeling studies on the reaction of 1 with dative ligands suggest a mechanism involving initial formation of dicobaltacyclohexanones A and B. B then is postulated to rearrange to a mononuclear carbonylmetallacyclobutane complex (C) which can either eliminate C3 hydrocarbons or undergo CO insertion, leading to metallacyclopentanone.
