@article {1263,
	title = {Synthesis and reactivity of zirconium and hafnium complexes incorporating chelating diamido-N-heterocyclic-carbene ligands},
	journal = {Journal of Organometallic Chemistry},
	volume = {690},
	number = {24-25},
	year = {2005},
	note = {ISI Document Delivery No.: 994VFTimes Cited: 36Cited Reference Count: 51},
	month = {Dec},
	pages = {5788-5803},
	type = {Article},
	abstract = {Early transition metal complexes employing a diamido N-heterocyclic carbene (NHC) ligand set (denoted [NCN]) render the centrally disposed NHC moiety stable to dissociation. Aminolysis reactions with the mesityl-substituted ligand precursor ((Mes)[NCN]H-2) and M(NMe2)(4) (M = Zr, Hf) provide bis(amido)-NHC-metal complexes that can be further converted to chloro and alkyl derivatives. Activation of (Mes)[NCN]M(CH3)(2) with [Ph3C][B(C6F5)(4)] yields {(Mes)[NCN]MCH3} {B(C6F5)(4)}, which is surprisingly inactive for the polymerization of 1-hexene. The zirconium cation did, however, show moderate ability to catalytically polymerize ethylene. The hafnium dialkyls are thermally stable with the exception of the diethyl complex, (Mes)[NCN]Hf(CH2CH3)(2), which undergoes P-hydrogen transfer and subsequent C-H bond activation with an ortho-methyl substituent on the mesityl group. The hafnium dialkyl complexes also insert carbon monoxide and substituted isocyanides to yield eta(2)-acyls and eta(2)-iminoacyls, respectively. In some circumstances, further C-C bond coupling occurs to yield enediolates and eneamidolate metallocycles. The molecular structures of (Mes)[NCN]Hf(CH2CHMe2)(2), (Mes)[NCN]Hf(eta(2)-(2,6-Me2C6H3NCCH3)(CH3), (Mes)[NCN]Hf(eta(2)-(2,6-Me2C6H3NCCH3)(2), (Mes)[NCN]Hf(OC(CH3)=C(CH3)NXy), and [(Mes)[NCN]Hf(OC(Bu-i)=C(Bu-i)O)](2) are included. (c) 2005 Elsevier B.V. All rights reserved.},
	keywords = {AMIDO, CARBON-MONOXIDE, CHEMISTRY, DONORS, ETA-2-IMINOACYL, hafnium, LIVING POLYMERIZATION, MIGRATORY INSERTION, N-heterocyclic carbene, OLEFIN, POLYMERIZATION, PROPERTIES, SPECTROSCOPIC, STABLE CARBENES, STRUCTURAL-CHARACTERIZATION, tridentate ligand, ZIRCONIUM, ZIRCONOCENE COMPLEXES},
	isbn = {0022-328X},
	url = {<Go to ISI>://000234058600046},
	author = {Spencer, L. P. and Fryzuk,Michael D.}
}
@article {4052,
	title = {The versatility of lithium reagents in synthetic organometallic chemistry: Their differing reactions with [(CpMo)-Mo-*(NO)(CH2SiMe3)(2)]},
	journal = {Chemistry-a European Journal},
	volume = {3},
	number = {10},
	year = {1997},
	note = {ISI Document Delivery No.: YA856Times Cited: 13Cited Reference Count: 44},
	month = {Oct},
	pages = {1579-1587},
	type = {Article},
	abstract = {[Cp*Mo(NO)(CH2SiMe3)(2)] exhibits three principal types of reaction with the various lithium reagents investigated during this study, namely: regioselective deprotonation, reduction, and addition. Deprotonation of the reactant, achieved by treatment with lithium amide reagents, leads ultimately to the formation of the alkylidene {\textquoteright}{\textquoteright}ate{\textquoteright}{\textquoteright} complex [Cp*Mo(NO)(CH2SiMe3)(=CHSiMe3)](2)[Li-2(thf)(3)] (1). While LiN(SiMe3)(2) effects this conversion directly with no detectable intermediates, reaction with 1 equiv of LDA in THF for 15 min deprotonates the Cp* ligand to form the lithium salt of the {\textquoteright}{\textquoteright}tucked-in{\textquoteright}{\textquoteright} ate complex [(eta(5),eta(1)C(5)Me(4)CH(2))Mo(NO)(CH2SiMe3)(2)][Li(thf)(3)] (2) in 40\% isolated yield, Complex 2 slowly converts to the thermodynamically more stable 1 when left as a THF or C6D6 solution at ambient temperature fbr 48 h. Reaction of the dialkyl starting material with either tBuLi or PhLi leads to the production of the alkylidene complex 1 in irreproducible yields (10-50\% NMR; not isolable). A kinetic analysis of the reaction of [Cp*Mo(NO)(CH2SiMe3)(2)] with LiN(SiMe3)(2) indicated that the reaction was first-order in both the lithium and molybdenum reagents, and the activation parameters of Delta H-double dagger = 7,3 +/- 1.0 kcal mol(-1) and Delta S (double dagger) = -34 +/- 3 e.u. suggest an associative process. Treatment of the neutral dialkyl with 1 equiv of LiPPh2, in THF results in a one-electron reduction and production of {[Cp*Mo(NO)(CH2SiMe3)(2)][Li(thf)]}(2) (3). If left in solution, the 17e(-) dialkyl anion 3 is converted to the 18e(-) alkylidene anion 1 by the Ph2P-PPh2 coproduct, which effects the requisite hydrogen-atom abstraction. Finally, addition of a sterically undemanding alkyllithium reagent such as MeLi to the 16e(-) dialkyl reactant leads to the formation of the 18e(-) trialkyl anionic complex [Cp*Mo(NO)(CH2SiMe3)(2)(Me)][Li(thf)(3)] (4). Warming of 4 in a C6D6 solution results in loss of methane and production of 1. In most cases, the chemistry exhibited by the Mo system is duplicated by the analogous W congener, [Cp*W(NO)(CH2SiMe3)(2)]. The solid-state molecular structures of complexes 1 and 4 have been established by single-crystal X-ray crystallographic analyses.},
	keywords = {COMPLEXES, H BOND ACTIVATION, LIGAND, lithium, LIVING POLYMERIZATION, {ALKYLIDENE COMPLEXES},
	isbn = {0947-6539},
	url = {<Go to ISI>://A1997YA85600004},
	author = {Legzdins,Peter and Sayers, S. F.}
}
