Preparation and carbonyl-substitution reactions of hexacarbonyldicobalt-complexed 1,3-dioxa-2-silacyclohept-5-ynes and 1,3,8,10-tetraoxa-2,9-disilacyclotetradeca-5,12-diynes. X-Ray crystal structure of [(Ph3P)(OC)5Co2-{µ-(C2CH2OSiPh2OCH2)2}Co2(CO)5(PPh3)]

Abstract

Reactions between [Co₂(µ-HOCH₂C₂CH₂OH)L¹L²(CO)₄][L¹= L²= CO or L¹–L²= bis(diphenyl-phosphino)methane (dppm)] and SiR¹(R²)Cl₂(R¹= R²= Me or Ph; R¹= Me, R²= Ph) afford hexacarbonyldicobalt-complexed 1,3-dioxa-2-silacyclohept-5-ynes which undergo carbonyl substitution in the case of L¹= L²= CO with PPh₃ or dppm. Fast-atom-bombardment (FAB) mass spectral evidence indicates that the 2,2-diphenyl-1,3-dioxa-2-silacyclohept-5-yne complex and its monophosphine-substituted derivative are dimers which is confirmed by the X-ray crystal structure of the latter, [(Ph₃P)(OC)₅Co₂{µ-(C₂CH₂OSiPh₂OCH₂)₂}Co₂(CO)₅(PPh₃)], in which the phosphine ligands occupy axial positions on opposite sides of the fourteen-membered ring. Only monomers are identified in the mass spectra of the other compounds, but evidence for unseparated higher oligomers as minor products is found in the NMR spectra of the 2,2-dimethyl-1,3-dioxa-2-silacyclohept-5-yne complex and its monophosphine and dppm derivatives.