Metal–borane complexes are emerging as promising systems for study in the context of bifunctional catalysis. Herein we describe diphosphineborane nickel complexes that activate Si–H bonds and catalyze the hydrosilylation of aldehydes. Treatment of [^(Mes)DPB^(Ph)]Ni (1) ([^(Mes)DPB^Ph] = ^(Mes)B(o-Ph_2PC_6H_4)_2) with organosilanes affords the complexes [^(Mes)DPB^(Ph)](μ-H)NiE (E = SiH_2Ph (3), SiHPh_2 (4)). Complex 4 is in solution equilibrium with 1 and the thermodynamic and kinetic parameters of their exchange have been characterized by NMR spectroscopy. Complex 1 is a catalyst for the hydrosilylation of a range of para-substituted benzaldehydes. Mechanistic studies on this reaction via multinuclear NMR spectroscopy are consistent with the intermediacy of a borohydrido-Ni-siloxyalkyl species

Harman, W. Hill

MacMillan, Samantha N.

Peters, Jonas C.

Caltech Authors - Main

 1 
Facile Si–H Bond Activation and Hydrosilylation Catalysis Mediated by a Nickel-
Borane Complex 
 
SUPPORTING INFORMATION 
 
Samantha N. MacMillan, W. Hill Harman, and Jonas C. Peters* 
 
Variable temperature van’t Hoff study of the equilibrium of 1 and 4 ...................................... 2	  
Variable temperature van’t Hoff study of the equilibrium of 1 and [MesDPBPh](D)NiSiDPh2 
(4-D) ................................................................................................................................................. 3	  
2D 1H-1H EXSY study of the equilibrium of 1 and 4 .................................................................. 4	  
X-ray Crystallography ................................................................................................................... 8	  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Electronic Supplementary Material (ESI) for Chemical Science
This journal is © The Royal Society of Chemistry 2013
 2 
 
Variable temperature van’t Hoff study of the equilibrium of 1 and 4  
 
Ferrocene and 4 were dissolved in toluene-d8 and transferred to a sealed J. Young NMR 
tube.  The tube was inserted into a temperature controlled NMR probe and 1H NMR 
spectra were collected at 10 K intervals from 328 K to 368 K, allowing 20 minutes for 
equilibration at each temperature. Concentrations of 1 and 4 were determined by 
integration of the mesityl aryl C-H resonance for the respective complexes and silane 
concentration was assumed to be equal to [1]. The equilibrium constant of the reaction 
was calculated according to the expression: 𝐾!"# = [𝟒][𝟏]! 
The plot of ln(Kobs) as a function of T-1 was fit by a line according to the expression: 𝑙𝑛 𝐾!"# = −∆𝐻𝑅𝑇 + ∆𝑆𝑅  
The enthalpy and entropy of the reaction were extracted from the slope and intercept, 
respectively.  
 
 
Fig. 1 Van’t Hoff plot derived from variable temperature 1H NMR spectra of the equilibrium 
between 1 and 4 from 328 K to 358 K. 
 
 
 
 
2.75 2.8 2.85 2.9 2.95 3 3.05
1000/T (1/K)
3.5
4
4.5
5
5.5
ln(
K e
q)
y = 6.276x - 13.707
R2 = 0.999
Electronic Supplementary Material (ESI) for Chemical Science
This journal is © The Royal Society of Chemistry 2013
 3 
Variable temperature van’t Hoff study of the equilibrium of 1 and 
[MesDPBPh](D)NiSiDPh2 (4-D) 
 
Ferrocene, D2SiPh2 and 1 were dissolved in toluene-d8 and transferred to a sealed J. 
Young NMR tube.  The tube was inserted into a temperature controlled NMR probe and 
1H NMR spectra were collected at 10 K intervals from 298 K to 358 K, allowing 20 
minutes for equilibration at each temperature. Concentrations of 1 and 4-D were 
determined by integration of the mesityl aryl C-H resonance for the respective complexes 
and silane concentration was assumed to be equal to [1]. 
 
 
Figure 2. Van’t Hoff plot derived from variable temperature 1H NMR spectra of the equilibrium 
between 1 and 4-D from 298 K to 358 K. 
 
 
 
 
 
 
 
 
 
 
 
 
 
2.8 2.9 3 3.1 3.2 3.3
1000/T (1/K)
5
6
7
8
9
10 y = 10.132x - 23.763
R2 = 0.999
ln(
K e
q)
Electronic Supplementary Material (ESI) for Chemical Science
This journal is © The Royal Society of Chemistry 2013
 4 
2D 1H-1H EXSY study of the equilibrium of 1 and 4 
 
2D 1H-1H EXSY spectra were collected using the samples prepared for the variable 
temperature experiments outlined above. To determine the exchange rates of the 
equilibrium between 1 and 4, two 2D EXSY experiments were acquired (mixing time 
(Tm) = 0 ms and 700 ms) at a number of temperatures. A representative example is shown 
below: 
 
Figure 3. 1H-1H EXSY spectrum recorded at 348 K with Tm = 700 ms in toluene-d8. 
 
 
 
 
		













	
	








Electronic Supplementary Material (ESI) for Chemical Science
This journal is © The Royal Society of Chemistry 2013
 5 
 
Figure 4. Expansion of the mesityl-H region. The peaks corresponding to 1 and 4 are labelled and 
dashed lines have been drawn to their cross-peaks for ease of viewing. Peaks have also been 
labeled with a letter code that corresponds to its position in the matrix of the EXSY CALC 
program.1 
 
The areas of the peaks were determined by integration. These raw values were introduced 
to EXSY CALC, the rate exchange matrices calculated and the magnetization rates (k1’ 
and k-1’) determined.  
 
Table 1. Raw volumes and magnetization rate constants. 
328 K 
Tm = 0 ms Tm = 700 ms 
k1’ (s-1) 
0.156 
k-1’ (s-1) 
0.548 
f2 f1 ID Volume f2 f1 ID Volume 
6.34 6.34 A 1.00 6.34 6.34 A 7.53 
5.62 5.62 B 0.51 5.62 5.62 B 1.73 
 6.34 5.62 A-B 1.00 
5.62 6.34 B-A 0.56 
 
338 K 
Tm = 0 ms Tm = 700 ms 
k1’ (s-1) 
0.357 
k-1’ (s-1) 
0.742 
f2 f1 ID Volume f2 f1 ID Volume 
6.34 6.34 A 1.60 6.33 6.34 A 4.24 
5.62 5.63 B 1.00 5.62 5.62 B 1.48 
 6.33 5.62 A-B 1.00 
5.62 6.33 B-A 0.77 
 
348 K 
Tm = 0 ms Tm = 700 ms 
k1’ (s-1) 
0.794 
k-1’ (s-1) 
1.187 
f2 f1 ID Volume f2 f1 ID Volume 
6.33 6.33 A 1.00 6.34 6.33 A 2.12 
5.62 5.63 B 0.76 5.62 5.62 B 1.18 
 6.33 5.62 A-B 1.00 
5.62 6.33 B-A 0.88 
 
 
		


	






	










1, B 
B-A 
A-B 
4, A 
Electronic Supplementary Material (ESI) for Chemical Science
This journal is © The Royal Society of Chemistry 2013
 6 
358 K 
Tm = 0 ms Tm = 700 ms 
k1’ (s-1) 
1.459 
k-1’ (s-1) 
1.459 
f2 f1 ID Volume f2 f1 ID Volume 
6.33 6.33 A 0.95 6.33 6.33 A 1.28 
5.62 5.62 B 1.00 5.62 5.62 B 1.25 
 6.33 5.62 A-B 1.00 
5.62 6.33 B-A 0.95 
 
Recall that the equilibrium exchange process of interest is: 
 
 
The magnetization rates k1’ and k-1’ were converted to chemical exchange rates via the 
following relationships: 𝑘! = 𝑘!![𝑠𝑖𝑙𝑎𝑛𝑒]                                     𝑘!! = 𝑘!!!                                     𝐾!"" = 𝑘!𝑘!! 
 
 
 
Table 2. Comparison of rate data obtained from EXSY experiments and the variable temperature 
van’t Hoff analysis. 
 
T k1 (s-1M-1) k-1 (s-1) Kapp (M-1) Keq (M-1) a 
328 43 0.16 270 230 
338 51 0.36 140 130 
348 67 0.79 85 80 
358 73 1.40 50 49 
a Keq as determined by the variable temperature van’t Hoff analysis 
Ni SiHPh2
PPh2
PPh2
H
B
Ph2P Ni
P
Ph2
B
H2SiPh2
k1
k-1
Electronic Supplementary Material (ESI) for Chemical Science
This journal is © The Royal Society of Chemistry 2013
 7 
 
Figure 5. Eyring plot for the forward reaction derived from variable temperature 1H-1H EXSY 
NMR spectra of the equilibrium between 1 and 4 from 328 K to 358 K. 
 
Figure 6. Eyring plot for the reverse reaction derived from variable temperature 1H-1H EXSY 
NMR spectra of the equilibrium between 1 and 4 from 328 K to 358 K. 
 
2.75 2.8 2.85 2.9 2.95 3 3.05 3.1
1000/T (1/K)
-2.4
-2.2
-2
-1.8
-1.6
-1.4
-1.2
-1
y = -1.931x + 3.889
R2 = -0.980ln(
k 1
/T
)
2.75 2.8 2.85 2.9 2.95 3 3.05 3.1
1000/T (1/K)
-7.5
-7
-6.5
-6
-5.5
ln(
k -
1/
T)
y = -8.597x + 18.628
R2 = 0.998
Electronic Supplementary Material (ESI) for Chemical Science
This journal is © The Royal Society of Chemistry 2013
 8 
X-ray Crystallography 
 
Low-temperature single crystal X-ray diffraction studies were carried out at the Beckman 
Institute Crystallography Facility on a Bruker Kappa Apex II diffractometer with Mo Kα 
radiation (λ = 0.71073 Å). Crystals were coated with Paratone-N oil and mounted on 
glass fibers. Structures were solved by direct or Patterson methods using SHELXS1 and 
refined against F2 on all data by full-matrix least squares with SHELXL-972 using 
established refinement techniques.3 All non-hydrogen atoms were refined anisotropically. 
All hydrogen atoms (except the hydrogen atoms bound to heteroatoms in 3-6) were 
included into the model at geometrically calculated positions and refined using a riding 
model. The isotropic displacement parameters of all calculated hydrogen atoms were 
fixed to 1.2 times the U values of the atoms they are linked to (1.5 times for methyl 
groups). Thermal ellipsoid diagrams were created using PyMOL.4 In the structure of 3, 
the OEt2 solvent molecule was disordered over two sites. The structure of 5 contained 
one positionally disordered toluene solvent molecule. The toluene molecule was refined 
anisotropically, however hydrogen atoms were not added due to the complicated nature 
of the positional disorder. Relevant details for individual data collections are reported in 
Tables 3-5. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                                                
1 G. M. Sheldrick, Acta Crystallogr. 1990, A46, 467.   
2 G. M. Sheldrick, Acta Crystallogr. 2008, A64, 112.  . . ,  . , , . 
3 P. Müller, Crystallogr. Rev. 2009, 15, 57. 
4 The PyMOL Molecular Graphics System, Version 1.5.0.4, Schrödinger, LLC. 
Electronic Supplementary Material (ESI) for Chemical Science
This journal is © The Royal Society of Chemistry 2013
 9 
Table 3. Crystal data and structure refinement for 3  OEt2 
 
Identification code 3  OEt2 
Empirical formula  C26.50 H26 B0.50 Ni0.50 O0.25 P Si0.50 
Formula weight  428.25 
Temperature  100(2) K 
Wavelength  0.71073 Å 
Crystal system  Triclinic 
Space group  P-1 
Unit cell dimensions a = 11.6097(8) Å α = 68.361(4)° 
 b = 13.0379(9) Å β = 72.030(4)° 
 c = 17.3875(12) Å γ = 64.875(4)° 
Volume 2178.5(3) Å
3
 
Z 4 
Density (calculated) 1.306 Mg/m
3
 
Absorption coefficient 0.584 mm
-1
 
F(000) 902 
Crystal size 0.27 x 0.18 x 0.11 mm 
Theta range for data collection 1.90 to 30.51° 
Index ranges -16<=h<=16, -18<=k<=18, -24<=l<=24 
Reflections collected 105776 
Independent reflections 13243 [Rint = 0.0472] 
Completeness to theta = 30.51° 99.6 %  
Absorption correction Empirical 
Max. and min. transmission 0.9385 and 0.8577 
Refinement method Full-matrix least-squares on F2 
Data / restraints / parameters 13243 / 0 / 564 
Goodness-of-fit on F
2
 1.036 
Final R indices [I>2σ(I)] R1 = 0.0358, wR2 = 0.0831 
R indices (all data) R1 = 0.0467, wR2 = 0.0904 
Largest diff. peak and hole             0.479 and -0.544 e.Å
-3 
 
 
 
 
 
 
 
Electronic Supplementary Material (ESI) for Chemical Science
This journal is © The Royal Society of Chemistry 2013
 10 
 
 
 
 
Figure 7. Fully labeled ORTEP diagram of 3. Thermal ellipsoids are drawn at 50% probability. 
Hydrogen atoms bound to carbon and solvent molecule are omitted for clarity. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Electronic Supplementary Material (ESI) for Chemical Science
This journal is © The Royal Society of Chemistry 2013
 11 
Table 4. Crystal data and structure refinement for 4  0.5 C6H6 
 
Identification code  4  0.5 C6H6 
Empirical formula  C60 H54 B Ni P2 Si 
Formula weight  934.58 
Temperature  100(2) K 
Wavelength  0.71073 Å 
Crystal system  Triclinic 
Space group  P-1 
Unit cell dimensions a = 12.1452(6) Å α = 69.986(3)° 
 b = 20.3316(10) Å β = 77.017(3)° 
 c = 21.4335(11) Å γ = 82.180(3)° 
Volume 4835.7(4) Å
3
 
Z 4 
Density (calculated) 1.284 Mg/m
3
 
Absorption coefficient 0.532 mm
-1
 
F(000) 1964 
Crystal size 0.41 x 0.13 x 0.08 mm 
Theta range for data collection 1.72 to 26.02° 
Index ranges -14<=h<=14, -25<=k<=25, -26<=l<=26 
Reflections collected 107064 
Independent reflections 19001 [Rint = 0.0675] 
Completeness to theta = 26.02° 99.8 %  
Absorption correction Empirical 
Max. and min. transmission 0.9607 and 0.8114 
Refinement method Full-matrix least-squares on F
2
 
Data / restraints / parameters 19001 / 0 / 1193 
Goodness-of-fit on F
2
 1.021 
Final R indices [I>2σ(I)] R1 = 0.0442, wR2 = 0.1065 
R indices (all data) R1 = 0.0686, wR2 = 0.1192 
Largest diff. peak and hole 1.754 and -0.610 e.Å
-3
 
 
 
 
 
 
 
 
Electronic Supplementary Material (ESI) for Chemical Science
This journal is © The Royal Society of Chemistry 2013
 12 
 
 
 
 
 
 
 
Figure 8. Fully labeled ORTEP diagram of 4. Thermal ellipsoids are drawn at 50% probability. 
Hydrogen atoms bound to carbon and solvent molecule are omitted for clarity. Only one of the 
two independent molecules is shown. 
 
 
 
 
 
 
 
 
 
 
 
 
 
Electronic Supplementary Material (ESI) for Chemical Science
This journal is © The Royal Society of Chemistry 2013
 13 
Table 5. Crystal data and structure refinement for 5  C7  
  
Identification code                  5  C7 
Empirical formula                    C55.50 H45 B Ni O P2 
Formula weight                       859.38 
Temperature                          100(2) K 
Wavelength                           0.71073 Å 
Crystal system     Monoclinic 
Space group      P2(1)/n 
Unit cell dimensions                 a = 12.9166(8) Å    α = 90° 
                                           b = 15.2418(9) Å     β = 105.256(3)° 
                                           c = 22.8933(15) Å    γ = 90° 
Volume                               4348.2(5) Å3 
Z        4 
Density(calculated)    1.313 Mg/m3 
Absorption coefficient              0.561 mm-1 
F(000)                               1796 
Crystal size                        0.24 x 0.22 x 0.17 mm 
Theta range for data collection     2.11 to 42.16° 
Limiting indices                     -24<=h<=24, -28<=k<=28, -43<=l<=39 
Reflections collected    250827 
Independent reflections       30670 [Rint = 0.0536] 
Completeness to theta = 42.16       99.9 % 
Absorption correction               Empirical 
Max. and min. transmission          0.9132 and 0.8772 
Refinement method                   Full-matrix least-squares on F2 
Data / restraints / parameters      30670 / 0 / 585 
Goodness-of-fit on F2              1.025 
Final R indices [I>2sigma(I)]       R1 = 0.0385, wR2 = 0.0935 
R indices (all data)                 R1 = 0.0710, wR2 = 0.1058 
Largest diff. peak and hole         0.688 and -0.445 e.A-3 
 
 
 
 
 
 
 
Electronic Supplementary Material (ESI) for Chemical Science
This journal is © The Royal Society of Chemistry 2013
 14 
 
 
 
 
 
 
 
Figure 9. Fully labeled ORTEP diagram of 5. Thermal ellipsoids are drawn at 50% probability. 
Hydrogen atoms bound to carbon and solvent molecule are omitted for clarity.  
 
Electronic Supplementary Material (ESI) for Chemical Science
This journal is © The Royal Society of Chemistry 2013


Facile Si–H bond activation and hydrosilylation catalysis mediated by a nickel–borane complex

English

https://authors.library.caltech.edu/43544/1/c3sc52626g.pdf

Facile Si–H bond activation and hydrosilylation catalysis mediated by a nickel–borane complex

Abstract

Similar works

Full text

Available Versions

Caltech Authors - Main

Caltech Authors - Main