Journal of the American Chemical Society
Article
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34) Initial turnover frequency was calculated by determining the
̈
lscher, M.; Pan, F.; Leitner, W. J. Am. Chem.
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12) For recent examples of catalytic noncooperative polar bond
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̈
̈
̈
(
3
(
initial reaction rate through line fitting of product concentration during
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15) Although NaBH4 in carboxylic acid media provides some
(
̈
35) (a) Arrowsmith, M.; Hadlington, T. J.; Hill, M. S.; Kociok-Kohn,
2
G. Chem. Commun. 2012, 48, 4567. (b) Hadlington, T. J.; Hermann,
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(
(
7
c) Oluyadi, A. A.; Ma, S.; Muhoro, C. N. Organometallics 2013, 32,
0.
36) Under the same reaction conditions (25 °C, C D ), H (100
selectivity for nitriles, the acidic conditions are not compatible with
many substrates. See: Gribble, G. W. Chem. Soc. Rev. 1998, 27, 395.
(
Hiebert, S.; Wang, T. C.; Wang, Y.; Liu, Y.; Clark, C. G.; Wong, H. S.;
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16) Jeon, Y. T.; Yang, W.; Qiao, J. X.; Li, L.; Ruel, R.; Thibeault, C.;
6
6
2
psi) or NaBH did not react with benzonitrile to form benzylamine.
4
(
̈
37) (a) Arrowsmith, M.; Hill, M. S.; Hadlington, T.; Kociok-Kohn,
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39) Due to the pKa difference between 1 and 2, the same
1
(
(
17) (a) Eisenberger, P.; Bailey, A. M.; Crudden, C. M. J. Am. Chem.
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42) We note that these orders are defined at the high substrate
(
concentrations used during the initial portion of catalysis. At low
concentrations (<0.5 and <0.2 M for HBPin and PhCN, respectively),
there is a positive correlation between concentration and the initial
rate.
(
19) Takaoka, A.; Mendiratta, A.; Peters, J. C. Organometallics 2009,
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(
(
20) Steiner, T. Angew. Chem., Int. Ed. 2002, 41, 48.
21) Desrosiers, P. J.; Cai, L.; Lin, Z.; Richards, R.; Halpern, J. J. Am.
(43) Compound 11 is proposed to engage in an equilibrium reaction
Chem. Soc. 1991, 113, 4173.
22) The 1:2 integration of the hydride to OH protons, as well as the
absence of any other low-T resonances, is not consistent with a Ru−
prior to the turnover limiting step. Other reactions in the catalytic
cycle likely also participate in equilibrium reactions with substrates,
consistent with the observed saturation kinetics in HBPin and PhCN
at high concentrations.
(
1
(
H ) intermediate under these conditions.
2
(
23) (a) Jarek, R. L.; Flesher, R. J.; Shin, S. K. J. Chem. Educ. 1997,
(44) While an inner sphere pathway is also possible, the high
74, 978. (b) Henry, R. M.; Shoemaker, R. K.; DuBois, D. L.; DuBois,
concentration of coordinatively saturated 11 in solution, in addition to
the minimal activity observed for 7 in the presence of 9, suggest an
outer sphere pathway may be more likely.
M. R. J. Am. Chem. Soc. 2006, 128, 3002. (c) Hulley, E. B.; Helm, M.
L.; Bullock, R. M. Chem. Sci. 2014, 5, 4729.
(
24) In many recent reports (see ref 25), low temperature exchange
(
45) Compounds containing heteroatom−boron bonds have gained
rates have been scaled to 293 K through speculative estimates of
activation entropy, which may lead to inflated extrapolated rates.
Adopting similar treatment, our rate at 293 K is 1.9 × 10 s rather
than 520 s . The large negative entropy value in 5 may reflect of a loss
of electronic entropy and symmetry in the transition state for hydride
protonation.
recent interest as organic synthons. See: Hirner, J. J.; Faizi, D. J.; Blum,
S. A. J. Am. Chem. Soc. 2014, 136, 4740. Chong, E.; Blum, S. A. J. Am.
Chem. Soc. 2015, 137, 10144.
5
−1
−1
(46) The diborylamine products react with benzaldehyde to form
2
(
25) (a) Liu, T.; Wang, X.; Hoffmann, C.; DuBois, D. L.; Bullock, R.
PhCH N(BCat) , see ref 17b.
2
2
M. Angew. Chem., Int. Ed. 2014, 53, 5300. (b) Hulley, E. B.; Welch, K.
D.; Appel, A. M.; DuBois, D. L.; Bullock, R. M. J. Am. Chem. Soc. 2013,
1
(
35, 11736.
26) Curtis, C. J.; Miedaner, A.; Ciancanelli, R.; Ellis, W. W.; Noll, B.
C.; Rakowski DuBois, M.; DuBois, D. L. Inorg. Chem. 2003, 42, 216.
27) There is one previously reported bifurcated intramolecular
(
hydrogen bond in a metal complex, with a long H−H contact of 1.8 Å.
Park, S.; Ramachandran, R.; Lough, A. J.; Morris, R. H. J. Chem. Soc.,
Chem. Commun. 1994, 2201.
G
J. Am. Chem. Soc. XXXX, XXX, XXX−XXX