@article {1573,
	title = {Inner-sphere two-electron reduction leads to cleavage and functionalization of coordinated dinitrogen},
	journal = {Proceedings of the National Academy of Sciences of the United States of America},
	volume = {103},
	number = {46},
	year = {2006},
	note = {ISI Document Delivery No.: 108OPTimes Cited: 14Cited Reference Count: 55Spencer, Liam P. MacKay, Bruce A. Patrick, Brian O. Fryzuk, Michael D.},
	month = {Nov},
	pages = {17094-17098},
	type = {Article},
	abstract = {Activation of molecular nitrogen by transition metal complexes is an area of current interest as investigations using the inert N-2 molecule to produce higher-value organonitrogen compounds intensify. In an attempt to extend the addition of hydride reagents E-H (where E = BR2, AIR(2), and SiR3) to the dinitrogen complex ([NPN]Ta)(2)(mu-H)(2)(mu-eta(2):eta(2)-N-2) [1; where NPN = (PhNSiMe2CH2)(2)PPh], the reaction with zirconocene chlorohydride, [Cp2Zr(Cl)H](x), was examined. The crystalline product formed in 35\% yield was determined to be ([NP(N)N]Ta)(mu-H)(2)(mu-N)(Ta[NPN])(ZrCP2) (2) in which the coordinated N-2 has been cleaved to form a phosphinimide bridging between Ta and Zr and a triply bridging nitride. The mechanism of this reaction was examined to determine the fate of the chloride and hydricle ligands attached to Zr in the starting zirconocene reagent. Using the zirconocene dihydride dimer ([Cp2ZrH2](2)), a higher yield of 2 was obtained (76\%), and H-2 was also observed by H-1 NMR spectroscopy. To probe the origin of the eliminated H-2, the dideuterated dinitrogen complex ([NPN]Ta)(2)(tLID)(2)(mu-eta(1):n(2)-N-2) (d(2)-1) was allowed to react with ([CP2ZrH2](2)), which resulted in the formation of ([NP(N)N]Ta)(mu-D)(2)(mu-N)(Ta[NPN]) (ZrCP2), (d(2)-2), with no evidence of hydrogen for deuterium scrambling between the starting zirconocene dihydride and the ditantalum dinitrogen complex. Studies into the use of preformed Zr(II) and Ti(II) reagents were also performed. The proposed mechanism involves initial adduct formation that facilitates inner-sphere electron transfer to cleave the N-N bond to form a species with bridging nitrides, one of which is transformed by nucleophilic attack of a phosphine donor to generate the observed phosphinimide.},
	keywords = {BOND-CLEAVAGE, BRIDGING N-2 UNIT, CLEAVAGE, COMPLEXES, dinitrogen coordination, END-ON, METAL-COMPLEXES, MOLECULAR, MOLYBDENUM-IRON PROTEIN, NITROGEN, nitrogen fixation, nitrogen-nitrogen bond, PHOSPHINIMIDE COMPLEXES, SIDE-ON, TANTALUM COMPLEX, TUNGSTEN},
	isbn = {0027-8424},
	url = {<Go to ISI>://000242249400008},
	author = {Spencer, L. P. and MacKay, B. A. and Patrick, B. O. and Fryzuk,Michael D.}
}
@article {1014,
	title = {Mechanisms of Staudinger reactions within density functional theory},
	journal = {J. Org. Chem.},
	volume = {69},
	number = {13},
	year = {2004},
	note = {ISI Document Delivery No.: 831IDTimes Cited: 25Cited Reference Count: 96},
	month = {Jun},
	pages = {4299-4308},
	type = {Article},
	abstract = {<p>The Staudinger reactions of substituted phosphanes and azides have been investigated by using density functional theory. Four different initial reaction mechanisms have been found. All systems studied go through a cis-transition state rather than a trans-transition state or a one-step transition state. The one-step pathway of the phosphorus atom attacking the substituted nitrogen atom is always unfavorable energetically. Depending on the substituents on the azide and the phosphane, the reaction mechanism with the lowest initial reaction barrier can be classified into three categories: (1) like the parent reaction, PH3 + N3H, the reaction goes through a cis-transition state, approaches a cis-intermediate, overcomes a PN-bond-shifting transition state, reaches a four-membered ring intermediate, dissociates N-2 by overcoming a small barrier, and results in the final products: N-2 and a phosphazene; (2) once reaching the cis-intermediate, the reaction goes through the N-2-eliminating transition state and produces the final products; (3) the reaction has a concerted initial cis-transition state, in which the phosphorus atom attacks the first and the third nitrogen atoms of the azide simultaneously and reaches an intermediate, and then the reaction goes through similar steps of the first reaction mechanism. In contrast to the previous predictions on the relative stability of the unsubstituted cis-configured phosphazide intermediate and the unsubstituted trans-configured phosphazide intermediate, the total energy of the substituted trans-configured phosphazide intermediate is close to that of the substituted cis-configured phosphazide intermediate. The preference of the initial cis-transition state reaction pathway is thoroughly discussed. The relative stability of the cis- and the trans-intermediates is explored and analyzed with the aid of molecular orbitals. The effects of substituents and solvent effects on the reaction mechanisms of the Staudinger reactions are discussed in detail.</p>},
	keywords = {AB-INITIO, GAS-PHASE, GAUSSIAN-TYPE BASIS, GOLD(I) COMPLEXES, METAL-COMPLEXES, MOLECULAR-ORBITAL METHODS, ORGANIC-MOLECULES, PHOSPHINIMIDE COMPLEXES, TRIAZADIENYL FLUORIDE, X-RAY CRYSTAL},
	isbn = {0022-3263},
	url = {<Go to ISI>://000222187200003},
	author = {Tian, W. Q. and Y. A. Wang*}
}
