@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 {3100,
	title = {COMPETITIVE REACTIVITY OF W-C, W-N, AND W-O BONDS AT THE CP-ASTERISK-W(NO) FRAGMENT - INSERTION REACTIONS OF TERT-BUTYL ISOCYANIDE, P-TOLYL ISOCYANATE, AND CARBON-DISULFIDE},
	journal = {Organometallics},
	volume = {13},
	number = {2},
	year = {1994},
	note = {ISI Document Delivery No.: MX338Times Cited: 26Cited Reference Count: 35},
	month = {Feb},
	pages = {569-577},
	type = {Article},
	abstract = {{The three related complexes, Cp*W(NO)(CH2CMe3)(NHCMe3) (1), Cp*W(NO)(OCMe3)-(NHCMe3) (2), and Cp*W(NO)(OCMe3)(CH2CMe3) (3), which differ only in the nature of the pair of groups alpha to the metal center, have been treated with tert-butyl isocyanide, p-tolyl isocyanate, and carbon disulfide in order to establish the relative tendencies of the W-C, W-N, and W-O linkages to undergo insertions of these reagents. The only site of insertion for tert-butyl isocyanide is the W-C bond, the W-N and W-O linkages being unreactive toward this substrate. In contrast, the preferential site of insertion for the two heterocumulenes, p-tolyl isocyanate, and carbon disulfide, was found to be W-N > W-O > W-C and W-N congruent-to W-C > W-O, respectively. These observations can be rationalized in terms of two different mechanisms being operative, one involving initial adduct formation at the metal center and the other involving direct attack at the tungsten-element bond undergoing the insertion. The tert-butyl isocyanide reactions proceed predominantly via the former mechanism, the p-tolyl isocyanate reactions proceed predominantly via the latter mechanism, and the carbon disulfide reactions proceed via both mechanistic pathways simultaneously. Consistently, a kinetic investigation of the reaction between complex 2 and p-tolyl isocyanate reveals that the reaction is second-order overall and first-order in 2 in the presence of an excess of isocyanate, findings indicative of a simple bimolecular reaction between 2 and the isocyanate. The solid-state molecular structure of Cp*W(NO)(eta2-C{NCMe3}CH2CMe3)(OCMe3) (5), formed by the reaction of 3 with tert-butyl isocyanide, has been established by a single-crystal X-ray diffraction analysis. Crystals of 5 are orthorhombic, space group Pbca, with a = 17.459(2) angstrom},
	keywords = {CHEMISTRY, COMPLEXES, ETA-2-IMINOACYL},
	isbn = {0276-7333},
	url = {<Go to ISI>://A1994MX33800031},
	author = {Legzdins,Peter and Rettig, S. J. and Ross, K. J.}
}
