An Exploration of the Acid-Catalyzed Interconversion of Mo(NAr)(CR1R2)(OR)2 Complexes and Their Mo(NAr)(Olefin)(OR)2 Isomers (Ar=2,6-i-Pr2C6H3, OR = OSiPh3 or OAr)

Four new Mo(NAr)(CR1R2)(OSiPh3)(2) complexes(Ar = 2,6-i-Pr2C6H3; CR1R2 = CMe2, CMeCH2Ph, CEtPh, or CHCH2Ph) were prepared through addition of CH2 CR1R2to a neopentylidene or a neophylidene complex. Three new olefin complexeswith the formula Mo(NAr)(olefin)(OSiPh3)(2) wereprepared from Mo(NAr)(CH2 CH2)(OSiPh3)(2), namely, Mo(NAr)(trans-CH3CH CHPh)(OSiPh3)(2), Mo(NAr)(CH2 CMePh)(OSiPh3)(2), and Mo(NAr)(CH2 CHCMe3)(OSiPh3)(2).Syntheses of other olefin complexes were complicated by relativelyfacile cis/trans isomerization of the olefin andisomerization of the C C bond within the olefin carbon chain.Addition of [(Et2O)(2)H][B(C6F5)(4)] to the alkylidene complexes generates cationic12e alkyl complexes [Mo(NAr)(CHMe2)(OSiPh3)(2)](+), [Mo(NAr)(CHMeCH2Ph)(OSiPh3)(2)](+), [Mo(NAr)(CHEtPh)(OSiPh3)(2)](+), and [Mo(NAr)(CH2CH2Ph)(OSiPh3)(2)](+). Deprotonation of the cationicalkyl complexes by NEt3 generates the disubstituted alkylidenecomplexes as the major product. In the case of [Mo(NAr)(CHMeCH2Ph)(OSiPh3)(2)](+), both Mo(NAr)(CMeCH2Ph)(OSiPh3)(2) and Mo(NAr)(CH2 CHCH2Ph)(OSiPh3)(2) are formedinitially ([alkylidene]/[olefin] = 1.5:1), but the latter then isomerizesto Mo(NAr)(CH3CH CHPh)(OSiPh3)(2). [Mo(NAr)(CHMePh)(OAr)(2)][B(C6F5)(4)] was prepared through the protonation of Mo(NAr)(CMePh)(OAr)(2) with [(Et2O)(2)H][B(C6F5)(4)]. Mo(NAr)(CMePh)(OAr)(2) does not reactwith [PhNMe2H][B(C6F5)(4)] at room temperature. Mo(NAr)(CH2 CH2)(OAr)(2) decomposes in solution at room temperature toyield Mo(NAr)(OAr)(& eta;(1),& eta;(2)-2-isopropyl-6-(prop-1-en-2-yl)phenolate)(Et2O) through CH activation in the isopropyl group of the OArligand followed by loss of ethane; Mo(NAr)(CH2 CHPh)(OAr)(2) decomposes similarly. Eight single-crystal X-ray diffractionstudies are reported.