### Abstract

Activation of N_{2} by (silox)_{3}Ta (1, silox = ^{t}Bu_{3}SiO) to afford (silox)_{3}Ta=N-N=Ta(silox) _{3} (1_{2}-N_{2}) does not occur despite ΔG°_{cald} = -55.6 kcal/mol because of constraints of orbital symmetry, prompting efforts at an independent synthesis that included a study of REH_{2} activation (E = N, P, As). Oxidative addition of REH _{2} to 1 afforded (silox)_{3}HTaEHR (2-NHR, R = H, Me, ^{n}Bu, C_{6}H_{4}-p-X (X = H, Me, NMe_{2}); 2-PHR, R = H, Ph; 2-AsHR, R = H, Ph), which underwent 1,2-H_{2}- elimination to form (silox)_{3}Ta=NR (1=NR; R = H, Me, ^{n}Bu, C_{6}H_{4}-p-X (X = H (X-ray), Me, NMe_{2}, CF _{3})), (silox)_{3}Ta=PR (1=PR; R = H, Ph), and (silox) _{3}Ta=AsR (1=AsR; R = H, Ph). Kinetics revealed NH bond-breaking as critical, and As > N > P rates for (silox)_{3}HTaEHPh (2-EHPh) were attributed to (1) ΔG°_{calc}(N) < ΔG° _{calc}(P) ∼ ΔG°_{calc}(As); (2) similar fractional reaction coordinates (RCs), but with RC shorter for N < P∼As; and (3) stronger TaE bonds for N > P∼As. Calculations of the pnictidenes aided interpretation of UV-vis spectra. Addition of H_{2}NNH_{2} or H_{2}N-N(^{c}NC_{2}H_{3}Me) to 1 afforded 1=NH, obviating these routes to 1_{2}-N_{2}, and formation of (silox)_{3}MeTaNHNH2 (4-NHNH_{2}) and (silox) _{3}MeTaNH(-^{c}NCHMeCH_{2}) (4-NH(azir)) occurred upon exposure to (silox)_{3}Ta=CH_{2} (1=CH_{2}). Thermolyses of 4-NHNH_{2} and 4-NH(azir) yielded [(silox)_{2}TaMe](μ- N_{α}HN_{β})(μ-N_{γ}HN _{δ}H)[Ta(silox)_{2}] (5) and [(silox)_{3}MeTa] (μ-η^{2}-N,N: η^{1}-C-NHNHCH_{2}CH _{2}CH_{2})[Ta(κ-O,C-OSi^{t}Bu_{2}CMe _{2}CH_{2})(silox)_{2}] (7, X-ray), respectively. (silox)_{3}Ta=CPPh_{3} (1=CPPh_{3}, X-ray) was a byproduct from Ph_{3}PCH_{2} treatment of 1 to give 1=CH _{2}. Addition of Na(silox) to [(THF)_{2}Cl_{3}Ta] _{2}(μ-N_{2}) led to [(silox)_{2}ClTa](μ-N _{2}) (8-Cl), and via subsequent methylation, [(silox) _{2}MeTa]_{2}(μ-N_{2}) (8-Me); both dimers were thermally stable. Orbital symmetry requirements for N_{2} capture by 1 and pertinent calculations are given.

Original language | English (US) |
---|---|

Pages (from-to) | 8524-8544 |

Number of pages | 21 |

Journal | Inorganic Chemistry |

Volume | 49 |

Issue number | 18 |

DOIs | |

State | Published - Sep 20 2010 |

Externally published | Yes |

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### ASJC Scopus subject areas

- Inorganic Chemistry
- Physical and Theoretical Chemistry

### Cite this

_{3}Ta (silox =

^{t}Bu

_{3}SiO); Attempts to circumvent the constraints of orbital symmetry in N

_{2}activation.

*Inorganic Chemistry*,

*49*(18), 8524-8544. https://doi.org/10.1021/ic101147x

**Pnictogen-hydride activation by (silox) _{3}Ta (silox = ^{t}Bu_{3}SiO); Attempts to circumvent the constraints of orbital symmetry in N_{2} activation.** / Hulley, Elliott B.; Bonanno, Jeffrey B.; Wolczanski, Peter T.; Cundari, Thomas R.; Lobkovsky, Emil B.

Research output: Contribution to journal › Article

_{3}Ta (silox =

^{t}Bu

_{3}SiO); Attempts to circumvent the constraints of orbital symmetry in N

_{2}activation',

*Inorganic Chemistry*, vol. 49, no. 18, pp. 8524-8544. https://doi.org/10.1021/ic101147x

_{3}Ta (silox =

^{t}Bu

_{3}SiO); Attempts to circumvent the constraints of orbital symmetry in N

_{2}activation. Inorganic Chemistry. 2010 Sep 20;49(18):8524-8544. https://doi.org/10.1021/ic101147x

}

TY - JOUR

T1 - Pnictogen-hydride activation by (silox)3Ta (silox = tBu3SiO); Attempts to circumvent the constraints of orbital symmetry in N2 activation

AU - Hulley, Elliott B.

AU - Bonanno, Jeffrey B.

AU - Wolczanski, Peter T.

AU - Cundari, Thomas R.

AU - Lobkovsky, Emil B.

PY - 2010/9/20

Y1 - 2010/9/20

N2 - Activation of N2 by (silox)3Ta (1, silox = tBu3SiO) to afford (silox)3Ta=N-N=Ta(silox) 3 (12-N2) does not occur despite ΔG°cald = -55.6 kcal/mol because of constraints of orbital symmetry, prompting efforts at an independent synthesis that included a study of REH2 activation (E = N, P, As). Oxidative addition of REH 2 to 1 afforded (silox)3HTaEHR (2-NHR, R = H, Me, nBu, C6H4-p-X (X = H, Me, NMe2); 2-PHR, R = H, Ph; 2-AsHR, R = H, Ph), which underwent 1,2-H2- elimination to form (silox)3Ta=NR (1=NR; R = H, Me, nBu, C6H4-p-X (X = H (X-ray), Me, NMe2, CF 3)), (silox)3Ta=PR (1=PR; R = H, Ph), and (silox) 3Ta=AsR (1=AsR; R = H, Ph). Kinetics revealed NH bond-breaking as critical, and As > N > P rates for (silox)3HTaEHPh (2-EHPh) were attributed to (1) ΔG°calc(N) < ΔG° calc(P) ∼ ΔG°calc(As); (2) similar fractional reaction coordinates (RCs), but with RC shorter for N < P∼As; and (3) stronger TaE bonds for N > P∼As. Calculations of the pnictidenes aided interpretation of UV-vis spectra. Addition of H2NNH2 or H2N-N(cNC2H3Me) to 1 afforded 1=NH, obviating these routes to 12-N2, and formation of (silox)3MeTaNHNH2 (4-NHNH2) and (silox) 3MeTaNH(-cNCHMeCH2) (4-NH(azir)) occurred upon exposure to (silox)3Ta=CH2 (1=CH2). Thermolyses of 4-NHNH2 and 4-NH(azir) yielded [(silox)2TaMe](μ- NαHNβ)(μ-NγHN δH)[Ta(silox)2] (5) and [(silox)3MeTa] (μ-η2-N,N: η1-C-NHNHCH2CH 2CH2)[Ta(κ-O,C-OSitBu2CMe 2CH2)(silox)2] (7, X-ray), respectively. (silox)3Ta=CPPh3 (1=CPPh3, X-ray) was a byproduct from Ph3PCH2 treatment of 1 to give 1=CH 2. Addition of Na(silox) to [(THF)2Cl3Ta] 2(μ-N2) led to [(silox)2ClTa](μ-N 2) (8-Cl), and via subsequent methylation, [(silox) 2MeTa]2(μ-N2) (8-Me); both dimers were thermally stable. Orbital symmetry requirements for N2 capture by 1 and pertinent calculations are given.

AB - Activation of N2 by (silox)3Ta (1, silox = tBu3SiO) to afford (silox)3Ta=N-N=Ta(silox) 3 (12-N2) does not occur despite ΔG°cald = -55.6 kcal/mol because of constraints of orbital symmetry, prompting efforts at an independent synthesis that included a study of REH2 activation (E = N, P, As). Oxidative addition of REH 2 to 1 afforded (silox)3HTaEHR (2-NHR, R = H, Me, nBu, C6H4-p-X (X = H, Me, NMe2); 2-PHR, R = H, Ph; 2-AsHR, R = H, Ph), which underwent 1,2-H2- elimination to form (silox)3Ta=NR (1=NR; R = H, Me, nBu, C6H4-p-X (X = H (X-ray), Me, NMe2, CF 3)), (silox)3Ta=PR (1=PR; R = H, Ph), and (silox) 3Ta=AsR (1=AsR; R = H, Ph). Kinetics revealed NH bond-breaking as critical, and As > N > P rates for (silox)3HTaEHPh (2-EHPh) were attributed to (1) ΔG°calc(N) < ΔG° calc(P) ∼ ΔG°calc(As); (2) similar fractional reaction coordinates (RCs), but with RC shorter for N < P∼As; and (3) stronger TaE bonds for N > P∼As. Calculations of the pnictidenes aided interpretation of UV-vis spectra. Addition of H2NNH2 or H2N-N(cNC2H3Me) to 1 afforded 1=NH, obviating these routes to 12-N2, and formation of (silox)3MeTaNHNH2 (4-NHNH2) and (silox) 3MeTaNH(-cNCHMeCH2) (4-NH(azir)) occurred upon exposure to (silox)3Ta=CH2 (1=CH2). Thermolyses of 4-NHNH2 and 4-NH(azir) yielded [(silox)2TaMe](μ- NαHNβ)(μ-NγHN δH)[Ta(silox)2] (5) and [(silox)3MeTa] (μ-η2-N,N: η1-C-NHNHCH2CH 2CH2)[Ta(κ-O,C-OSitBu2CMe 2CH2)(silox)2] (7, X-ray), respectively. (silox)3Ta=CPPh3 (1=CPPh3, X-ray) was a byproduct from Ph3PCH2 treatment of 1 to give 1=CH 2. Addition of Na(silox) to [(THF)2Cl3Ta] 2(μ-N2) led to [(silox)2ClTa](μ-N 2) (8-Cl), and via subsequent methylation, [(silox) 2MeTa]2(μ-N2) (8-Me); both dimers were thermally stable. Orbital symmetry requirements for N2 capture by 1 and pertinent calculations are given.

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U2 - 10.1021/ic101147x

DO - 10.1021/ic101147x

M3 - Article

VL - 49

SP - 8524

EP - 8544

JO - Inorganic Chemistry

JF - Inorganic Chemistry

SN - 0020-1669

IS - 18

ER -