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

Abstract

Addition of one equiv of water to Mo(CAr)[OCMe(CF 3 ) 2 ] 3 (1,2 - dimethoxyethane) ( 2, Ar = o-(OMe)C 6 H 4 ) in the presence of PPhMe 2 leads to formation of Mo(O)(CHAr)[OCMe(CF 3 ) 2 ] 2 (PPhMe 2 ) ( 3(PPhMe 2 ) ) in 3 4 % yield. Addition of one equiv of water alone to 2 produces the dimeric alkylidyne hydroxide complex, { Mo(CAr)[OCMe(CF 3 ) 2 ] 2 ( [mu]-OH)}2(dme) ( 4(dme)) in which each bridging hydroxide proton points toward an oxygen atom in an aryl methoxy group. Addition of PMe 3 to 4(dme) gives the alkylidene oxo complex, (3(PMe 3)), ananalog of 3(PPhMe 2)(95% conversion, 66% isolated). Treatment of 3(PMe 3) with two equiv of HCl gave Mo(O)(CHAr)Cl 2 (PMe 3)(5), which upon addition of LiO-2,6-(2,4,6-i-Pr 3 C 6 H 2) 2C 6 H 3 (LiOHIPT) gave Mo(O)(CHAr)(OHIPT)Cl(PMe 3)(6). Compound 6 in the presence of B(C6F5)3 will initiate the ring - opening metathesis polymeri- zation of cyclooctene, 5,6 - dicarbomethoxynorbornadiene (DCMNBD), and rac-5,6-dicarbomethoxynorbornene (DCMNBE), and the homocouplin g of 1-decene to 9-octa decene. 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 2 ), 4(dme), and 6.