@article {616,
	title = {Reduction of hafnium(IV) complexes in the presence of molecular nitrogen: Attempts to form dinitrogen complexes of the heaviest group 4 element},
	journal = {Canadian Journal of Chemistry-Revue Canadienne De Chimie},
	volume = {81},
	number = {11},
	year = {2003},
	note = {ISI Document Delivery No.: 746YXTimes Cited: 10Cited Reference Count: 28},
	month = {Nov},
	pages = {1376-1387},
	type = {Article},
	abstract = {The reaction of [P2N2]Li-2(dioxane)(2) with HfCl4(THF)(2) (where [P2N2] = PhP(CH2SiMe2NSiMe2CH2)(2)PPh) results in the formation of the hafnium dichloride complex [P2N2]HfCl2 (1). The behaviour of 1 as a potential precursor in the generation of a dinitrogen coordination complex is described. Reduction of 1 with potassium-graphite (C8K), under dinitrogen, under a variety of conditions led to a number of products, one of which is the dinuclear derivative with bridging P-phenyl groups that has the general formula {[P2N2]Hf}(2) (2). Reduction of the hafnium diiodide [P2N2]HfI2 (3) - prepared via the reaction of 1 with excess Me3SiI - with C8K results in the formation of ([P2N2]Hf)(2)(mu-eta(2):eta(2)-N-2) (4) as the major product of the reaction, while {[P2N2]Hf}(2) (2) and [P2N2]Hf(C7H8) (5) appear to be minor products. Reaction of 1 with 2 equiv of MeMgCl gives [P2N2]HfMe2 (6), which, upon exposure to an atmosphere of H-2, gives the hafnium tetrahydride {[P2N2]Hf}(2)(m-H)(4) (7).},
	keywords = {COORDINATION CHEMISTRY, DERIVATIVES, DINITROGEN, donor ligands, FLUXIONAL BEHAVIOR, hafnium, hydride, macrocycle, mixed, {ALKYL},
	isbn = {0008-4042},
	url = {<Go to ISI>://000186777600031},
	author = {Fryzuk,Michael D. and Corkin, J. R. and Patrick, B. O.}
}
@article {5202,
	title = {Effects of sequential replacement of -NH2 by -OH in the tripodal tetraamine tren on its acidity and metal ion coordinating properties},
	journal = {Inorganic Chemistry},
	volume = {40},
	number = {7},
	year = {2001},
	note = {ISI Document Delivery No.: 413ATTimes Cited: 26Cited Reference Count: 32},
	month = {Mar},
	pages = {1527-1535},
	type = {Article},
	abstract = {The preparation is described of two modified derivatives of the tripodal tetraamine tren, 2-hydroxy-N,N-bis(2-aminoethyl)ethylamine, NNO(2)222, and 2-amino-N,N-bis(2-hydroxyethyl)ethylamine NNO(2)222, in which one and two primary amines, respectively, have been replaced with hydroxyl groups. The aqueous acid-base and metal ion (Ni2+, Cu2+: Zn2+ coordination properties of these two compounds were studied by potentiometric, spectrophotometric, and NMR titrations. Two and three acidity constants, respectively, were determined for NNO(2)222 and NN(2)O222 by potentiometry. NMR titrations proved that deprotonation of the two OH residues in NNO(2)222, and of the one in NN(2)O222, corresponded to pK(a) > 14. Acidity constants related to deprotonation-of the terminal primary amine functions were similar in both NNO2222 and NN(2)O222 land to those in the parent compound tren), whereas deprotonation of the tertiary ammonium N atom had a very different acidity constant in each of these three compounds. Charge repulsion, polar effects, and intramolecular hydrogen bond formation an responsible for the discrepancy. Chelated diamine metal complexes for each ligand studied depended only on the basicity of the corresponding two amines, suggesting that the hydroxyl group interacted with the metal ion very weakly in acidic or neutral solutions. The ML2+ species further deprotonated to form M(L - H)(+) and M(L - 2H) complexes, in which the protons are released from the coordinated OH group. A pM vs pH correlation showed that replacing an NH2 group with a OH group in tren or NN(2)O222 makes the resulting metal complex less stable. Electronic spectra showed that the Cu(II) complexes of both NNO(2)222 and NN(2)O222 adopted a square pyramidal geometry rather than a trigonal bipyramidal geometry. The X-ray crystal structure analysis of the zinc complex [Zn(OH)(mu -NNO(2)222 - H)Zn(NNO(2)222)](2+), as its [BF4](-) salt, shows a dinuclear molecule containing two zinc ions, each coordinated in a distorted trigonal bipyramid. The coordination environment at one zinc atom is composed of the four donor groups of a mono-O-deprotonated ligand NNO(2)222 and a hydroxyl ion with the central nitrogen atom of the ligand and the hydroxyl ion in equatorial positions. The oxygen atom of the deprotonated alkoxo group bridges to the second zinc atom, which is coordinated by this atom and one undeprotonated ligand NNO2222.},
	keywords = {COPPER(II) COMPLEXES, CRYSTAL, DIPERCHLORATE, donor ligands, STABILITY},
	isbn = {0020-1669},
	url = {<Go to ISI>://000167588300019},
	author = {Song, B. and Reuber, J. and Ochs, C. and Hahn, F. E. and Lugger, T. and Orvig, Chris}
}
