TY  - JOUR
AU  - Ninković, Dragan
AU  - Moncho, Salvador
AU  - Petrović, Predrag
AU  - Hall, Michael B.
AU  - Zarić, Snežana D.
AU  - Brothers, Edward N.
PY  - 2023
UR  - http://cherry.chem.bg.ac.rs/handle/123456789/6196
AB  - We present results for a series of complexes derived from a titanium complex capable of activating C–H bonds under mild conditions (PNP)Ti═CHtBu(CH2tBu), where PNP = N[2-PiPr2-4-methylphenyl]2–. In addition to the initial activation of methane, a tautomerization reaction to a terminal methylidene is also explored due to methylidene’s potential use as a synthetic starting point. Analogous complexes with other low-cost 3d transition metals were studied, such as scandium, titanium, vanadium, and chromium as both isoelectronic and isocharged complexes. Our results predict that V(IV) and V(V) complexes are promising for methane C–H bond activation. The V(V) complex has a low rate-determining barrier for methane activation, specifically 16.6 kcal/mol, which is approximately 12 kcal/mol less than that for the Ti complex, as well as having a moderate tautomerization barrier of 29.8 kcal/mol, while the V(IV) complex has a methane activation barrier of 19.0 kcal/mol and a tautomerization barrier of 31.1 kcal/mol. Scandium and chromium complexes are much poorer for C–H bond activation; scandium has very high barriers, while chromium strongly overstabilizes the alkylidene intermediate, potentially stopping the further reaction. In addition to the original PNP ligand, some of the most promising ligands from a previous work were tested, although (as shown previously) modification of the ligand does not typically have large effects on the activity of the system. Our best ligand modification improves the performance of the V(V) complex via the substitution of the nitrogen in PNP by phosphorus, which reduces the tautomerization barrier by 5 to 24.4 kcal/mol.
PB  - American Chemical Society
T2  - Inorganic Chemistry
T1  - Improving a Methane C–H Activation Complex by Metal and Ligand Alterations from Computational Results
VL  - 62
IS  - 13
SP  - 5058
EP  - 5066
DO  - 10.1021/acs.inorgchem.2c03342
ER  - 

@article{
author = "Ninković, Dragan and Moncho, Salvador and Petrović, Predrag and Hall, Michael B. and Zarić, Snežana D. and Brothers, Edward N.",
year = "2023",
abstract = "We present results for a series of complexes derived from a titanium complex capable of activating C–H bonds under mild conditions (PNP)Ti═CHtBu(CH2tBu), where PNP = N[2-PiPr2-4-methylphenyl]2–. In addition to the initial activation of methane, a tautomerization reaction to a terminal methylidene is also explored due to methylidene’s potential use as a synthetic starting point. Analogous complexes with other low-cost 3d transition metals were studied, such as scandium, titanium, vanadium, and chromium as both isoelectronic and isocharged complexes. Our results predict that V(IV) and V(V) complexes are promising for methane C–H bond activation. The V(V) complex has a low rate-determining barrier for methane activation, specifically 16.6 kcal/mol, which is approximately 12 kcal/mol less than that for the Ti complex, as well as having a moderate tautomerization barrier of 29.8 kcal/mol, while the V(IV) complex has a methane activation barrier of 19.0 kcal/mol and a tautomerization barrier of 31.1 kcal/mol. Scandium and chromium complexes are much poorer for C–H bond activation; scandium has very high barriers, while chromium strongly overstabilizes the alkylidene intermediate, potentially stopping the further reaction. In addition to the original PNP ligand, some of the most promising ligands from a previous work were tested, although (as shown previously) modification of the ligand does not typically have large effects on the activity of the system. Our best ligand modification improves the performance of the V(V) complex via the substitution of the nitrogen in PNP by phosphorus, which reduces the tautomerization barrier by 5 to 24.4 kcal/mol.",
publisher = "American Chemical Society",
journal = "Inorganic Chemistry",
title = "Improving a Methane C–H Activation Complex by Metal and Ligand Alterations from Computational Results",
volume = "62",
number = "13",
pages = "5058-5066",
doi = "10.1021/acs.inorgchem.2c03342"
}

Ninković, D., Moncho, S., Petrović, P., Hall, M. B., Zarić, S. D.,& Brothers, E. N.. (2023). Improving a Methane C–H Activation Complex by Metal and Ligand Alterations from Computational Results. in Inorganic Chemistry
American Chemical Society., 62(13), 5058-5066.
https://doi.org/10.1021/acs.inorgchem.2c03342

Ninković D, Moncho S, Petrović P, Hall MB, Zarić SD, Brothers EN. Improving a Methane C–H Activation Complex by Metal and Ligand Alterations from Computational Results. in Inorganic Chemistry. 2023;62(13):5058-5066.
doi:10.1021/acs.inorgchem.2c03342 .

Ninković, Dragan, Moncho, Salvador, Petrović, Predrag, Hall, Michael B., Zarić, Snežana D., Brothers, Edward N., "Improving a Methane C–H Activation Complex by Metal and Ligand Alterations from Computational Results" in Inorganic Chemistry, 62, no. 13 (2023):5058-5066,
https://doi.org/10.1021/acs.inorgchem.2c03342 . .

TY  - JOUR
AU  - Ninković, Dragan
AU  - Moncho, Salvador
AU  - Petrović, Predrag
AU  - Zarić, Snežana D.
AU  - Hall, Michael B.
AU  - Brothers, Edward N.
PY  - 2016
UR  - https://cherry.chem.bg.ac.rs/handle/123456789/2281
AB  - The titanium neopentylidene complex (PNP)Ti=(CHBu)-Bu-t((CH2Bu)-Bu-t), PNP=N[2-(PPr2)-Pr-i-4-methylphenyl](2)(-), can activate both sp(2) and sp(3) C-H bonds under mild conditions. In this work, we studied the reaction mechanism of this complex with benzene and methane using modern density functional theory, specifically the B97XD functional which contains long-range exchange and dispersion corrections. The mechanism of the reaction is similar to that computed previously in the literature, but we describe a new conformer that is both more stable and kinetically more reactive. The four-step mechanism is very similar for both benzene and methane. However, the highest energy barriers differ; for methane, it is the last step, which elucidates the inertness of that reactant. In addition, the hydrogen exchange between alkyl and alkylidene ligands in methane's product was studied by two different mechanisms: tautomerization to form (PNP)(TiCHBu)-Bu-t(=CH2) and reverse C-H activation to form (PNP)(TiCBu)-Bu-t(CH3). The feasibility of the tautomerization, through a preliminary, accessible isomerization, suggests that these systems can be used to explore the reactivity of terminal methylidenes. Finally, methodological considerations are also discussed, as the importance of including the dispersion in the density functionals was determined by comparing several functionals. This comparison has shown that the dispersion is critical for accurate modeling, especially in the stability of the unsaturated intermediate; this has been neglected in previous studies. [GRAPHICS] .
PB  - Taylor & Francis Ltd, Abingdon
T2  - Journal of Coordination Chemistry
T1  - Carbon-hydrogen bond activation by a titanium neopentylidene complex
VL  - 69
IS  - 11-13
SP  - 1759
EP  - 1768
DO  - 10.1080/00958972.2016.1172701
ER  - 

@article{
author = "Ninković, Dragan and Moncho, Salvador and Petrović, Predrag and Zarić, Snežana D. and Hall, Michael B. and Brothers, Edward N.",
year = "2016",
abstract = "The titanium neopentylidene complex (PNP)Ti=(CHBu)-Bu-t((CH2Bu)-Bu-t), PNP=N[2-(PPr2)-Pr-i-4-methylphenyl](2)(-), can activate both sp(2) and sp(3) C-H bonds under mild conditions. In this work, we studied the reaction mechanism of this complex with benzene and methane using modern density functional theory, specifically the B97XD functional which contains long-range exchange and dispersion corrections. The mechanism of the reaction is similar to that computed previously in the literature, but we describe a new conformer that is both more stable and kinetically more reactive. The four-step mechanism is very similar for both benzene and methane. However, the highest energy barriers differ; for methane, it is the last step, which elucidates the inertness of that reactant. In addition, the hydrogen exchange between alkyl and alkylidene ligands in methane's product was studied by two different mechanisms: tautomerization to form (PNP)(TiCHBu)-Bu-t(=CH2) and reverse C-H activation to form (PNP)(TiCBu)-Bu-t(CH3). The feasibility of the tautomerization, through a preliminary, accessible isomerization, suggests that these systems can be used to explore the reactivity of terminal methylidenes. Finally, methodological considerations are also discussed, as the importance of including the dispersion in the density functionals was determined by comparing several functionals. This comparison has shown that the dispersion is critical for accurate modeling, especially in the stability of the unsaturated intermediate; this has been neglected in previous studies. [GRAPHICS] .",
publisher = "Taylor & Francis Ltd, Abingdon",
journal = "Journal of Coordination Chemistry",
title = "Carbon-hydrogen bond activation by a titanium neopentylidene complex",
volume = "69",
number = "11-13",
pages = "1759-1768",
doi = "10.1080/00958972.2016.1172701"
}

Ninković, D., Moncho, S., Petrović, P., Zarić, S. D., Hall, M. B.,& Brothers, E. N.. (2016). Carbon-hydrogen bond activation by a titanium neopentylidene complex. in Journal of Coordination Chemistry
Taylor & Francis Ltd, Abingdon., 69(11-13), 1759-1768.
https://doi.org/10.1080/00958972.2016.1172701

Ninković D, Moncho S, Petrović P, Zarić SD, Hall MB, Brothers EN. Carbon-hydrogen bond activation by a titanium neopentylidene complex. in Journal of Coordination Chemistry. 2016;69(11-13):1759-1768.
doi:10.1080/00958972.2016.1172701 .

Ninković, Dragan, Moncho, Salvador, Petrović, Predrag, Zarić, Snežana D., Hall, Michael B., Brothers, Edward N., "Carbon-hydrogen bond activation by a titanium neopentylidene complex" in Journal of Coordination Chemistry, 69, no. 11-13 (2016):1759-1768,
https://doi.org/10.1080/00958972.2016.1172701 . .