%0 Journal Article %1 Agarwala.2013 %A Agarwala, Hemlata %A Ehret, Fabian %A Chowdhury, Abhishek Dutta %A Maji, Somnath %A Mobin, Shaikh M. %A Kaim, Wolfgang %A Lahiri, Goutam Kumar. %D 2013 %J Dalton Transactions %K DFT aqua benzoquinonediimine calcn catalyst catalyst;ruthenium chloro complex complex;olefin crystal electrochem epoxidn methanetrispyrazole prepn ruthenium structure %N 10 %P 3721--3734 %R 10.1039/c2dt32402d %T Electronic structure and catalytic aspects of Ru(tpm)(bqdi)(Cl/H2O)n, tpm = tris(1-pyrazolyl)methane and bqdi = o-benzoquinonediimine %V 42 %X Diamagnetic Ru(tpm)(bqdi)(Cl)ClO4 (1ClO4) (tpm = tris(1-pyrazolyl)methane, bqdi = o-benzoquinonediimine) and Ru(tpm)(bqdi)(H2O)(ClO4)2 (2(ClO4)2) were synthesized. The valence state-sensitive bond distances of coordinated bqdi C-N: 1.311(5)/1.322(5) \AA in 1ClO4; 1.316(7)/1.314(7) \AA in mol. A and 1.315(6)/1.299(7) \AA in mol. B of 2(ClO4)2 imply its fully oxidized quinonediimine (bqdi0) character. DFT calcns. of 1+ confirm the RuII-bqdi0 vs. the antiferromagnetically coupled RuIII-bqdi√- alternative. The 1H NMR spectra of 1ClO4 in different solvents show variations in chem. shift positions of the NH (bqdi) and CH (tpm) proton resonances due to their different degrees of acidity in different solvents. In CH3CN/0.1 mol dm-3 Et4NClO4, 1ClO4 undergoes one reversible RuII .dblharw. RuIII oxidn. and two redns., the reversible first electron uptake being bqdi based (bqdi0/bqdi$\surd$-). The electrogenerated paramagnetic RuIII-bqdi0 (12+) and RuII-Q√- (1) exhibit RuIII-type (12+: \textlessg\textgreater = 2.211/Dg = 0.580) and radical-type (1: g = 1.988) EPR signals, resp., as is confirmed by calcd. spin densities (Ru: 0.767 in 12+, bqdi: 0.857 in 1). The aqua complex 2(ClO4)2 exhibits two 1-electron oxidns. at pH = 7, suggesting the formation of RuIV:O species. The electronic spectral features of 1n (n = charge assocd. with the different redox states of the chloro complex: 2+, 1+, 0) in CH3CN and of 22+ in H2O were interpreted based on the TD-DFT calcns. The application potential of the aqua complex 22+ as a pre-catalyst towards the epoxidn. of olefins was explored in the presence of the sacrificial oxidant PhI(OAc)2 in CH2Cl2 at 298 K, showing the desired selectivity with a wide variety of alkenes. DFT calcns. based on styrene as the model substrate predict that the epoxidn. reaction proceeds through a concerted transition state pathway. on SciFinder(R)

@article{Agarwala.2013, abstract = {Diamagnetic [Ru(tpm)(bqdi)(Cl)]ClO4 ([1]ClO4) (tpm = tris(1-pyrazolyl)methane, bqdi = o-benzoquinonediimine) and [Ru(tpm)(bqdi)(H2O)](ClO4)2 ([2](ClO4)2) were synthesized. The valence state-sensitive bond distances of coordinated bqdi [C-N: 1.311(5)/1.322(5) {\AA} in [1]ClO4; 1.316(7)/1.314(7) {\AA} in mol. A and 1.315(6)/1.299(7) {\AA} in mol. B of [2](ClO4)2] imply its fully oxidized quinonediimine (bqdi0) character. DFT calcns. of 1+ confirm the {RuII-bqdi0} vs. the antiferromagnetically coupled {RuIII-bqdi√-} alternative. The 1H NMR spectra of [1]ClO4 in different solvents show variations in chem. shift positions of the NH (bqdi) and CH (tpm) proton resonances due to their different degrees of acidity in different solvents. In CH3CN/0.1 mol dm-3 Et4NClO4, [1]ClO4 undergoes one reversible RuII .dblharw. RuIII oxidn. and two redns., the reversible first electron uptake being bqdi based (bqdi0/bqdi$\surd$-). The electrogenerated paramagnetic {RuIII-bqdi0} (12+) and {RuII-Q√-} (1) exhibit RuIII-type (12+: {\textless}g{\textgreater} = 2.211/\textgreek{D}g = 0.580) and radical-type (1: g = 1.988) EPR signals, resp., as is confirmed by calcd. spin densities (Ru: 0.767 in 12+, bqdi: 0.857 in 1). The aqua complex [2](ClO4)2 exhibits two 1-electron oxidns. at pH = 7, suggesting the formation of {RuIV:O} species. The electronic spectral features of 1n (n = charge assocd. with the different redox states of the chloro complex: 2+, 1+, 0) in CH3CN and of 22+ in H2O were interpreted based on the TD-DFT calcns. The application potential of the aqua complex 22+ as a pre-catalyst towards the epoxidn. of olefins was explored in the presence of the sacrificial oxidant PhI(OAc)2 in CH2Cl2 at 298 K, showing the desired selectivity with a wide variety of alkenes. DFT calcns. based on styrene as the model substrate predict that the epoxidn. reaction proceeds through a concerted transition state pathway. [on SciFinder(R)]}, added-at = {2022-06-15T11:26:56.000+0200}, author = {Agarwala, Hemlata and Ehret, Fabian and Chowdhury, Abhishek Dutta and Maji, Somnath and Mobin, Shaikh M. and Kaim, Wolfgang and Lahiri, Goutam Kumar.}, biburl = {https://puma.ub.uni-stuttgart.de/bibtex/2727254f323a53ae10a95ea3109f3d8b0/huebleriac}, doi = {10.1039/c2dt32402d}, interhash = {0985d2e9d0f121c64939bce49921d0f9}, intrahash = {727254f323a53ae10a95ea3109f3d8b0}, issn = {1477-9226}, journal = {Dalton Transactions}, keywords = {DFT aqua benzoquinonediimine calcn catalyst catalyst;ruthenium chloro complex complex;olefin crystal electrochem epoxidn methanetrispyrazole prepn ruthenium structure}, number = 10, pages = {3721--3734}, timestamp = {2022-06-15T09:26:56.000+0200}, title = {Electronic structure and catalytic aspects of [Ru(tpm)(bqdi)(Cl/H2O)]n, tpm = tris(1-pyrazolyl)methane and bqdi = o-benzoquinonediimine}, volume = 42, year = 2013 }