@article {1270,
	title = {Lewis adducts of the side-on end-on dinitrogen-bridged complex [{(NPN)Ta}(2)(mu-H)(2)(mu-eta(1):eta(2)-N-2)] with AlMe3, GaMe3, and B(C6F5)(3): Synthesis, structure, and spectroscopic properties},
	journal = {Chemistry-a European Journal},
	volume = {11},
	number = {2},
	year = {2005},
	note = {ISI Document Delivery No.: 887VLTimes Cited: 12Cited Reference Count: 49},
	month = {Jan},
	pages = {604-618},
	type = {Article},
	abstract = {{Reaction of the side-on end-on dinitrogen complex [{(NPN)Ta}(2)(mu- H)(2)(mu-eta(1):eta(2)-N-2)] (1; in which NPN= (PhNSiMe2CH2)(2)PPh), with the Lewis acids XR3 results in the adducts [{(NPN)Ta}(2)(mu-H)(2)(mu-eta(1):eta(2)-NNXR3)]},
	keywords = {CHEMISTRY, CLEAVAGE, COORDINATED, density functional calculations, DINITROGEN, DINITROGEN COMPLEXES, DINUCLEAR TANTALUM COMPLEX, EFFECTIVE CORE POTENTIALS, FIXATION, MOLECULAR CALCULATIONS, MOLYBDENUM CENTER, N-2 LIGAND, NITROGEN, Raman spectroscopy, REACTIVITY, tantalum, TRIS(PENTAFLUOROPHENYL)BORANE},
	isbn = {0947-6539},
	url = {<Go to ISI>://000226333500014},
	author = {Studt, F. and MacKay, B. A. and Johnson, S. A. and Patrick, B. O. and Fryzuk,Michael D. and Tuczek, F.}
}
@article {2801,
	title = {END-ON VERSUS SIDE-ON BONDING OF DINITROGEN TO DINUCLEAR EARLY TRANSITION-METAL COMPLEXES},
	journal = {Journal of the American Chemical Society},
	volume = {115},
	number = {7},
	year = {1993},
	note = {ISI Document Delivery No.: KW980Times Cited: 72Cited Reference Count: 55},
	month = {Apr},
	pages = {2782-2792},
	type = {Article},
	abstract = {{The preparation of a series of dinuclear complexes of zirconium and tantalum is presented in an effort to determine factors involved in the coordination mode of the bridging dinitrogen ligand. Reduction of ZrCl3[N(SiMe2-CH2PR2)2] (R = Pr(i) and B(t)) with Na/Hg under N2 generate the corresponding dinitrogen complexes {[(R2PCH2-SiMe2)2 SiMe2)2N]ZrCl}2(mu-eta2:eta2-N2); the X-ray crystal structure of the dark blue derivative having R = Pr(i) shows that the dinitrogen unit is bridging in a planar side-on bonding mode. The N-N bond distance is 1.548(7) angstrom, which is the longest such distance for any dinitrogen complex reported. Molecular orbital calculations on this molecule indicate that the N2 unit bonds in a side-on fashion due to the unavailability of one of the d orbitals on each zirconium that would normally be involved in a pi-bond with the antibonding pi*-orbitals of the N2 moiety. This particular zirconium d orbital is unavailable due to the ancillary tridentate ligand which positions the amide donor (and the chloride) to overlap effectively with this d orbital. The results of this MO study also show that the HOMO has delta-symmetry. When the related derivative Zr(eta5-C5H5)Cl2[N(SiMe2CH2PPri2)2] is reduced under N2, the corresponding dinuclear derivative {[(Pri2PCH2SiMe2)2N]Zr(eta5-C5H5)}2(mu-eta1:eta1-N2) has the bridging dinitrogen unit end-on. In this case, the MO analysis shows that the cyclopentadienyl ligand overlaps with that zirconium d orbital which could form the delta-molecular orbital of the side-on mode; as a result, the end-on form is generated. A similar argument can be used to rationalize the end-on binding mode of the dinitrogen unit in the related tantalum derivatives {[(Pri2PCH2SiMe2)2N]Ta=CHR}2(mu-eta1:eta1-N2) (R = Bu(t), Ph), since now the alkylidene unit effectively overlaps with the same d orbital Crystals of {[(Pri2PCH2-SiMe2)2N]ZrCl}(mu-eta2:eta2-N2)-CH3C6H5 are monoclinic},
	keywords = {ACTIVATION, CARBON BONDS, CHEMISTRY, MOLECULAR-STRUCTURE, N-2 LIGAND, NITROGEN-FIXATION, PHOSPHINE COMPLEXES, RAY CRYSTAL-STRUCTURE, TANTALUM COMPLEXES, X-RAY},
	isbn = {0002-7863},
	url = {<Go to ISI>://A1993KW98000028},
	author = {Fryzuk,Michael D. and Haddad, T. S. and Mylvaganam, M. and McConville, D. H. and Rettig, S. J.}
}
