SYNTHESES AND REACTIVITY OF HETEROMETALLIC OXO-ACETYLIDE CLUSTER COMPOUNDS - SKELETAL REARRANGEMENT AND CONVERSION OF ACETYLIDE TO ALKENYL,ALKYLIDENE, AND ALLENYL LIGANDS ON A WRE2 FRAMEWORK

Oxidation of the mixed-metal cluster CpWRe2(CCR)(CO)(9) (1, Cp* = C5M e5; R = Ph and C(Me)=CH2) with dioxygen in solution at 100 degrees C a ffords the oxo clusters CpW(O)Re-2(CCR)-(CO)(8), (2a, R = Ph; and 2b, R = C(Me)=CH2. Treatment of 2 with CO at 110 degrees C provides the c lusters CpW(O)Re-2(CCR)(CO)(9) (4), which revert back to 2 by removal of one CO upon thermolysis. Both compounds 2 and 4 contain an open tr iangular skeletal arrangement, a multisite bound acetylide ligand, and a terminal oxo ligand attached to the W atom. Complex 2a reacts with dihydrogen to form a mixture of three cluster complexes: the acetylide cluster CpWRe2(mu-O)(mu-H)(2)(CCPh)(CO)(6) (5a), alkenyl cluster Cp* W(O)Re-2(CHCHPh)(CO)(8) (6a), and the alkylidene cluster CpW(O)Re-2(m u-H)(CHCH2Ph)(CO)(8) (7a), which are formally produced by addition of two Ha and elimination of two CO molecules, transferring one H-2 to th e acetylide ligand and incorporation of one H-2 molecule to 6a, respec tively. For the vinylacetylide compound 2b, it reacts with dihydrogen under similar conditions to furnish a mixture of the above mentioned c lusters 5b, 6b, and 7b, together with a fourth allenyl cluster CpWRe2 (mu-O)(CHCCMe2)(CO)(7) (8), which is probably produced through a 1,3-H -migration on the alkenyl ligand CH=CHC(Me)=CH2 in 6b. The X-ray struc tural analysis of these oxo cluster compounds, their spectroscopic dat a, and the mechanistic studies of the conversion from acetylide cluste rs 2, 4, and 5 to alkenyl clusters 6, alkylidene clusters 7, and allen yl cluster 8 are presented.