59763-75-6Relevant academic research and scientific papers
Tantalum dioxide complexes with dinitrogen. formation and characterization of the side-on and end-on bonded TaO2(NN)x (x = 1-3) complexes
Wang, Caixia,Zhuang, Jia,Wang, Guanjun,Chen, Mohua,Zhao, Yanying,Zheng, Xuming,Zhou, Mingfei
, p. 8083 - 8089 (2011/02/17)
The reaction of tantalum dioxide molecule with dinitrogen has been studied by matrix isolation infrared spectroscopy. The tantalum dioxide molecules produced from laser evaporation of bulk Ta2O5 target reacted with dinitrogen to form the TaO2(η1-NN) x (x = 1-3) complexes on annealing, in which the N2 ligands are end-on bonded to the tantalum metal center. The TaO2(η 1-NN)3 complex decomposed to TaO2(η1-NN) 2 under infrared irradiation. The TaO2(η1- NN)2 and TaO2(η1-NN)3 complexes rearranged to the less stable TaO2(η1NN) (η2-N2) and TaO2((η1-NN) 2(η2-N2) isomers under visible light excitation. Both the mono- and bis-dinitrogen complexes were predicted to have 2A' or 2A1 ground states arising from, the 2A1 ground state of TaO2, whereas the two tridinitrogen complexes were predicted to have 2B2 ground states with C2v, symmetry, which are derived from the 2B1 excited state of TaO2.
Heavy water reactions with atomic transition-metal and main-group cations: Gas phase room-temperature kinetics and periodicities in reactivity
Cheng, Ping,Koyanagi, Gregory K.,Bohme, Diethard K.
, p. 8561 - 8573 (2008/10/09)
Reactions of heavy water, D2O, have been measured with 46 atomic metal cations at room temperature in a helium bath gas at 0.35 Torr using an inductively coupled plasma/selected ion flow tube tandem mass spectrometer. The atomic cations were produced at ca. 5500 K in an ICP source and were allowed to decay radiatively and thermalize by collisions with Ar and He atoms prior to reaction. Rate coefficients and product distributions are reported for the reactions of fourth-row atomic cations from K+ to Se+, of fifth-row atomic cations from Rb+ to Te+ (excluding Tc+), and of sixth-row atomic cations from Cs+ to Bi +. Primary reaction channels were observed leading to O-atom transfer, OD transfer, and D2O addition. O-Atom transfer occurs almost exclusively (≥90%) in the reactions with most early transition-metal cations (Sc+, Ti+, V+, Y+, Zr +, Nb+, Mo+, Hf+, Ta+, and W+) and to a minor extent (10%) with one main-group cation (As+). OD transfer is observed to occur only with three cations (Sr+, Ba+, and La+). Other cations, including most late transition and main-group cations, were observed to react with D 2O exclusively and slowly by D2O addition or not at all. O-Atom transfer proceeds with rate coefficients in the range of 8.1 × 10-13 (As+) to 9.5 × 10-10 (Y +) cm3 molecule-1 s-1 and with efficiencies below 0.1 and even below 0.01 for the fourth-row atomic cations V+ (0.0032) and As+ (0.0036). These low efficiencies can be understood in terms of the change in spin required to proceed from the reactant to the product potential energy surfaces. Higher order reactions are also measured. The primary products, NbO+, TaO+, MoO +, and WO+, are observed to react further with D 2O by O-atom transfer, and ZrO+ and HfO+ react further through OD group abstraction. Up to five D2O molecules were observed to add sequentially to selected M+ and MO+ as well as MO2+ cations and four to MO2D +. Equilibrium measurements for sequential D2O addition to M+ are also reported. The periodic variation in the efficiency (k/kc) of the first addition of D2O appears to be similar to the periodic variation in the standard free energy (ΔG°) of hydration.
Reactions of group V metal atoms with water molecules. Matrix isolation FTIR and quantum chemical studies
Zhou,Dong,Zhang,Qin
, p. 135 - 141 (2007/10/03)
Laser-ablated group V metal atoms (V, Nb, Ta) were co-deposited with water molecules in excess argon. The V atoms reacted with water to form the inserted HVOH molecule spontaneously. The Nb atoms reacted with water to form the NbOH2 complex and
Ammonolysis of tantalum alkyls: Formation of cubic TaN and a trimeric nitride, [Cp*MeTaN]3
Holl, Mark M. Banaszak,Kersting, Meinolf,Pendley, Bradford D.,Wolczanski, Peter T.
, p. 1518 - 1526 (2008/10/08)
Ammonolyses of precursor alkyl complexes have been employed to generate nitrides of tantalum. Treatment of (tBuCH2)3Ta= CHtBu (1) with NH3 led to the formation of an orange precipitate, best formulated as an oligomer, [TaN2.14H1.35]n (2), on the basis of ammonia uptake, neopentane loss, and combustion analysis. Upon thermolysis of 2 at 400°C (24 h), a ～6% weight loss occurred and amorphous TaN was generated; crystalline cubic TaN (Fm3m, 95%) was formed after further heating at 820°C (3 days). Under ambient light, a similar ammonolysis of 1 afforded another oligomer, [TaC1.41H3.90N1.90]n (2prime;); thermolysis of 2′ (400°C, 24 h) resulted in a ～14% weight loss and amorphous TaN that was subsequently annealed to pure, crystalline cubic TaN (820°C, 3 days, XRD, Fm3m). Cp*TaMe4 (3, Cp* = η5-C5Me5) was exposed to excess NH3 in order to model the ammonolysis process. The uptake of 1 equiv of ammonia/equiv of Ta was noted, 3 equiv of CH4 was released, and [Cp*MeTaN]3 (4) formed in 90% yield. Cyclic trimer 4 contains equivalent TaN distances (1.887 (17) A?) akin to those of related phosphazenes. Crystal data: monoclinic, P21/c, a = 16.951 (5) A?, b = 8.920 (3) A?, c = 23.141 (6) A?, β = 91.47 (2)°, Z = 4, T = -100°C. EHMO calculations revealed why a structure containing alternating double and single TaN bonds was not favored. The low-lying LUMO of 4 was predicted to be nonbonding; consequently, 4 was reduced with Na/K to yield [K·nEt2O]+[{Cp*MeTaN}3] - (5). A reversible reduction wave at E°′ = -2.5 V vs SSCE was also observed. Similar IR spectra of 4 (ν(TaNTa) = 960 cm-1) and 5 (ν(TaNTa) = 964 cm-1) support the contention that the LUMO is nonbonding. The relationship of 4 to the solid-state nitrides produced via ammonolysis is addressed.
