@article {2088,
	title = {Reactivity of Cp*Mo(NO)(= CHCMe3) with olefins and dienes: C-H activation reactions of molybdenacyclobutanes},
	journal = {Organometallics},
	volume = {27},
	number = {12},
	year = {2008},
	note = {ISI Document Delivery No.: 312BHTimes Cited: 5Cited Reference Count: 30Graham, Peter A. Buschhaus, Miriam S. A. Pamplin, Craig B. Legzdins, Peter},
	month = {Jun},
	pages = {2840-2851},
	type = {Article},
	abstract = {Reactions of a variety of cyclic and acyclic olefins with the title alkylidene complex (formed spontaneously by loss of neopentane from Cp*Mo(NO)(CH2CMe3)(2) under ambient conditions) result in the initial formation of molybdenacyclobutane complexes (Cp* = C5Me5). These molybdenacyclobutane complexes do not react via olefin metathesis or cyclopropanation pathways, but instead via C-H activation. Thus, when cyclopentene is the olefinic substrate, the direct result of C-H activation at the beta-position of the metallacyclobutane affords a thermally stable allyl hydrido complex that can be isolated. Such an allyl hydride intermediate is not isolable for larger cyclic olefins (cyclohexene, cycloheptene, and cyclooctene) or acyclic olefins (allylbenzene and 1-hexene). Instead, those complexes react further, undergoing a second C-H activation at the allylic position to produce eta(4)-trans-diene complexes concomitant with the loss of dihydrogen. Upon heating, these eta(4)-trans-diene complexes liberate diene, thereby enabling the 14e Cp*Mo(NO) metal fragment to catalyze the oligomerization of cyclic olefins and dienes including cyclohexene and 1,4-cyclohexadiene. In the case of the acyclic olefin allylbenzene, the metal fragment catalyzes a dimerization to (E)-(4-methylpent-1-ene-1,5-diyl)dibenzene under ambient conditions.},
	keywords = {ALPHA-HYDROGEN ABSTRACTION, BONDS, COMPLEXES, CRYSTAL-STRUCTURES, CYCLOHEXENE, METATHESIS, MOLYBDENUM, NEOPENTYLIDENE, OLIGOMERIZATION, TUNGSTEN},
	isbn = {0276-7333},
	url = {<Go to ISI>://000256643600023},
	author = {Graham, P. A. and Buschhaus, M. S. A. and Pamplin, C. B. and Legzdins,Peter}
}
@article {4543,
	title = {Mechanistic studies of the formation of zirconium alkylidene complexes [eta(5)-C5H3-1,3-(SiMe2CH2PPr2i)(2)]Zr=CHR(Cl) (R = Ph, SiMe3)},
	journal = {Journal of the American Chemical Society},
	volume = {121},
	number = {11},
	year = {1999},
	note = {ISI Document Delivery No.: 180AUTimes Cited: 33Cited Reference Count: 32},
	month = {Mar},
	pages = {2478-2487},
	type = {Article},
	abstract = {The reaction of [P2Cp]ZrCl3 (1) with 2 equiv of KCH2Ph generates an equilibrium mixture of alkyl complexes consisting of [P2Cp]ZrCl2(CH2Ph) (2), [P2Cp]ZrCl(CH2Ph)(2) (3), and [P2Cp]Zr(CH2Ph)(3) (4). Thermolysis of this mixture yields the alkylidene complex [P2Cp]Zr=CHPh(Cl) (5) in 85\% overall yield. Kinetic studies reveal a composite mechanism that incorporates the above preequilibrium, followed by an intramolecular alpha-abstraction reaction of dibenzyl 3 which follows a first-order rate, with the rate parameters Delta H double dagger = 19(1) kcal mol(-1) and Delta S double dagger = -22(5) cal(-1) mol K-1. A kinetic isotope effect of 3.0(5) was measured at 70 degrees C for the perdeuterated analogue [P2Cp]ZrCl(CD2C6D5)2. The reaction of 1 with 2 equiv of LiCH2-EMe3 (E = C, Si) produces a similar equilibrium mixture as observed for the benzyl analogues, consisting of [P2Cp]ZrCl2(CH2EMe3) (7), [P2Cp]Zr(CH2EMe3)(3) (8), and [P2Cp]ZrCl(CH2EMe3)(2) (9). Thermolysis of this mixture yields [P2Cp]Zr=CHEMe3(Cl) (6). A kinetic analysis conducted on 9 (E = Si) indicated a first-order reaction from which the activation parameters Delta H double dagger = 6(1) kcal mol(-1) and Delta S double dagger = -62(5) cal mol(-1) K-1 were obtained. The results indicate that reaction rates follow the order CH2Ph > CH2SiMe3 > CH2CMe3, an exact reversal of the trend for the homoleptic Ta systems Ta(CH2R)(5). The role of phosphine coordination is discussed to account for this trend. A crystal structure determination obtained for 6b reveals an alpha-agnostic interaction and a structure analogous to that of 5.},
	keywords = {ALPHA-HYDROGEN ABSTRACTION, CHEMISTRY, LIGAND, METAL-CARBON BONDS, NIOBIUM, OPENING METATHESIS POLYMERIZATION, tantalum, THERMOLYSIS, TITANIUM ALKYLIDENES, TITANOCENE},
	isbn = {0002-7863},
	url = {<Go to ISI>://000079363300019},
	author = {Fryzuk,Michael D. and Duval, P. B. and Mao, Sssh and Zaworotko, M. J. and Macgillivray, L. R.}
}
