REACTIONS OF DINUCLEAR AND POLYNUCLEAR COMPLEXES, XIX - REARRANGEMENTS OF TERMINAL OR DISUBSTITUTED ALKYNE LIGANDS PRESENT IN HOMODINUCLEARAND HETERODINUCLEAR COMPLEXES OF COBALT AND MOLYBDENUM DURING REACTIONS WITH MOLYBDENUM AND COBALT CARBONYL-COMPOUNDS - FORMATION OF TRINUCLEAR AND TETRANUCLEAR CLUSTERS

The dicobalt alkyne complex [Co-2(mu-PhC drop CH)(CO)(6)] 1a reacted w ith [Mo-2(eta(5)-C5H5)(2)CO)(4)] in refluxing tetrahydrofuran (THF) to give the mu(3)-alkylidyne trinuclear cluster [Co2Mo(eta(5)-C5H5)(mu(3 )-CCH2Ph)(CO)(8)] 3 as the major product. Possible routes to the forma tion of 3 have been investigated. Among the identified minor products from this reaction were [CoMo2(eta(5)-C5H5)(2)(eta(3)-CCH2Ph)(CO)(7)] 4, Mo2(eta(5)-C5H5)(2)(mu(4)-PhC2H)(mu-CO)(4)(CO)(4)] 5 and 3Mo(eta(5) -C5H5)(2)(mu(4)-PhC2H)(mu-CO)(2)(CO)(5)] 6. In contrast. when the rela ted dicobalt complexes [Co-2(mu-CF3C drop CR) (CO)(6)] (R = CF3 (1b), H (1c)), which contain alkynes with more strongly electron-withdrawing substituents, were heated with [Mo-2(eta(5)-C5H5)(2)(CO)(4)] in THF o nly mixed-dinuclear complexes (eta(5)-C5H5)(CO)(2)Mo(mu-CF3C2R)Co(CO)( 3)](Mo-Co) (R = H (7a), CF3 (7b)) were formed. The reaction of the mix ed-dinuclear complex 7b with [Co(eta(5)-C5H5)(CO)(2)] led to the mixed -tetranuclear butterfly cluster [Co2Mo2(eta(5)-C5H5)(3)(mu-CO)(CO)(3)] 8. The thermal reaction of 1b with the phosphido compound [Mo-2(eta(5 )-C5H5)(2)(mu-CO)(mu-PPh2)(2)] gave rise to a single product, )(mu-PPh 2){mu-PPh2Co2(mu-CF3C2CF3)(CO)(5)}(CO)(2)] 9, in which a phenyl ring o f the (mu-phosphido)dimolybdenum moiety is pi-bonded to one of the two cobalt atoms. Spectroscopic data for the new complexes are discussed. (C) 1998 Elsevier Science S.A. All rights reserved.