Syntheses of Molybdenum Oxo Alkylidene Complexes through Addition of Water to an Alkylidyne Complex.

Addition of one equiv of water to Mo(CAr)OCMe(CF) (2, Ar = o-(OMe)CH) in the presence of PPhMe leads to formation of Mo(O)(CHAr)OCMe(CF) (3(PPhMe)) in 34% yield. Addition of one equiv of water alone to 2 produces the dimeric alkylidyne hydroxide complex, {Mo(CAr)OCMe(CF)}(dme) (4(dme)) in which each bridging hydroxide proton points toward an oxygen atom in an arylmethoxy group. Addition of PMe to 4(dme) gives the alkylidene oxo complex, (3(PMe)), an analogue of 3(PPhMe) (95% conversion, 66% isolated). Treatment of 3(PMe) with two equiv of HCl gave Mo(O)(CHAr)Cl(PMe) (5), which upon addition of LiO-2,6-(2,4,6-i-PrCH)CH (LiOHIPT) gave Mo(O)(CHAr)(OHIPT)Cl(PMe) (6). Compound 6 in the presence of B(CF) will initiate the ring-opening metathesis polymerization of cyclooctene, 5,6-dicarbomethoxynorbornadiene (DCMNBD), and rac-5,6-dicarbomethoxynorbornene (DCMNBE), and the homocoupling of 1-decene to 9-octadecene. The poly(DCMNBD) has a cis,syndiotactic structure, whereas poly(DCMNBE) has a cis,syndiotactic,alt structure. X-ray structures were obtained for 3(PPhMe), 4(dme), and 6.