Ligand Exchange Reactions of Triphospholyl Metal Carbonyl Complexes

Abstract

Utilizing 1-triphenylstannyl-3,5-di(tert-butyl)-1,2,4-triphosphole (2) as the transfer reagent for the 1,2,4-triphospholyl ligand, the new cobalt dicarbonyl complex (η5-t-Bu2C2P3)(CO)2Co (4) has been prepared. The reactivity of 4 and that of triphosphacymantrene (η5-t-Bu2C2P3)(CO)3Mn (3) toward carbonyl exchange have been investigated. When 3 or 4 are photolyzed in the presence of phosphanes the mono- and disubstituted complexes (η5-t-Bu2C2P3)(CO)(PR3)Co (R = Et (5), Ph (6)) and (η5-t-Bu2C2P3)(CO)(PMe3)2Mn (7) are obtained. In the absence of additional ligands, the irradiation of 3 in n-hexane results in the formation of the dinuclear rac and meso complexes {μ[1:1−5-η-t-Bu2C2P3](CO)2Mn}2 (8a and 8b). Under thermal conditions the carbonyl ligands of both 3 and 4 are replaced by isonitrile ligands to yield (η5-t-Bu2C2P3)(CN−Cy)2Co (9), (η5-t-Bu2C2P3)(CO)(CN−Cy)Co (10), and (η5-t-Bu2C2P3)(CO)2(CN−Cy)Mn (11), respectively. The substances have been fully characterized including X-ray structural analysis for the complexes 4, 6, 7, 8a, 8b, and 9. Under both photochemical and thermal conditions the complexes 3 and 4 are much more reactive than their phosphorus-free cyclopentadienyl analogues. In contrast with cymantrene, triphosphacymantrene (3) seems to react via an associative pathway.