Ligand exchange reactions of triphospholyl metal carbonyl complexes

Utilizing 1-triphenylstannyl-3,5-di(tert-butyl)-1,2,4-triphosphole (2) as t he transfer reagent for the 1,2,4-triphospholyl ligand, the new cobalt dica rbonyl complex (eta (5)-t-BU2C2P3)(C)(2)CO (4) has been prepared. The react ivity of 4 and that of triphosphacymantrene (eta (5)-t-Bu2C2P3)(CO)(3)Mn (3 ) toward carbonyl exchange have been investigated. When 3 or 4 are photolyz ed in the presence of phosphanes the mono- and disubstituted complexes (eta (5)-t-BU2C2P3)(CO)(PR3)CO (R = Et (5), Ph (6)) and (eta (5)-t-Bu2C2P3)(CO) (PMe3)(2)Mn (7) are obtained. In the absence of additional ligands, the irr adiation of 3 in n-hexane results in the formation of the dinuclear rac and meso complexes {mu [1:1-5-eta -t-Bu2C2P3] (CO)(2)Mn}(2) (8a and 8b). Under thermal conditions the carbonyl ligands of both 3 and 4 are replaced by is onitrile ligands to yield (eta (5)-t-Bu2C2P3)(CN-Cy)(2)Co (9), (eta (5)-t-B u2C2P3)(CO)(CN-Cy)Co (10), and (eta (5)-t-BU2C2P3)-(CO)(2)(CN-Cy)Mn (11), r espectively. The substances have been fully characterized including X-ray s tructural analysis for the complexes 4, 6, 7, 8a, 8b, and 9. Under both pho tochemical and thermal conditions the complexes 3 and 4 are much more react ive than their phosphorus-free cyclopentadienyl analogues. In contrast with cymantrene, triphosphacymantrene (3) seems to react via an associative pat hway.