of 5
Supp
orting
Information for
Role of Ligand Protonation in Dihydrogen Evolution from a
Pentamethylcyclopentadienyl Rhodium Catalyst
Samantha I. Johnson
1,2
Harry B. Gray,
1
James D. Blakemore,
3,
* and William A. Goddard III
2,
*
1.
Center for Chemical Innovation
in Solar Fuels, California Institute of Technology,
Pasadena, CA 91125
2. Materials Research Center, California Institute of Technology, Pasadena, CA 91125
3. Department of Chemistry, University of Kansas, Lawrence, KS 66045
-
7582
* To whom correspondence
should be addressed.
E
-
mail: blakemore@ku.edu (JDB);
wag@wag.caltech.edu
(WAG). phone: +1
-
785
-
864
-
3019 (JDB); +1
-
626
-
395
-
3093
(WAG).
Contents
Appendix 1:
Scheme S1
:
Additional
P
rotonation
T
ransition
S
tates
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
...
.
1
Ap
pendix 2
:
Molecular
Geometries
.....................................................................
.
2
Appendix 3: Calculation
Details
..................................................................
.
...
.
...
.
3
1
Appendix 1: Scheme S1: Additional protonation transition states
Scheme S1:
Additional protonation states
TS 5
and
6
are shown.
Both direct attack by the
acid at the protonated Cp* ring
(
TS 6
)
and
the metathesis pathway (
TS
5
) feature barriers that are thermally inaccessible at room temperature.
In the case of
TS 6
,
protonation would lead directly to the evolution of hydrogen
, represented by
7
, without the
participation of the Rh center. However, at 43.8 kcal/mol above the singly
-
protonated Rh
I
complex, this is an insurmountable barrier. Alternatively, after the barrierless generation of
5
,
metathesis could occur
wherein the metal
-
bound proton and the Cp*
-
b
ound proton combine to
generate complex
6
. The barrier for this reaction is found to be 27.1 kcal/mol. By comparison,
TS 4
, which is featured in the manuscript, is 20.5 kcal/mol. Neither of these transition states are
reasonable when compared to the concer
ted pathways.
Rh
N
N
I
H
3
Rh
N
N
III
H
5
NCCH
3
Rh
N
N
III
6
H
H
5 =
4.0
-7.3
Free Energy [kcal/mol]
Reaction Coordinate
Rh
N
N
III
H
2
Rh
N
N
H
TS 4
H
Et
3
N
2+
TS 4
= 20.5
Rh
N
N
III
H
TS 3
H
DMF
Rh
N
N
III
7
NCCH
3
7 =
-16.9
+ H
2
TS 6
= 43.8
Rh
N
N
I
H
TS 6
H
A
2+
2 =
-1.1
Rh
N
N
III
H
H
2+
2+
TS 5
TS 5
= 27.1
H
0.91
1.47
6 =
-1.4
TS 3 =
7.3
2+
2+
2+
2
Ap
pendix 2: Molecular Geometries
Molecular geometries are contained in an additional supplemental file and are in the XYZ
format. The titles of the individual complexes correspond with complex names used in this
manuscript.
They can be
viewed using several free programs available online including Mercury
(
www.ccdc.cam.ac.uk/mercury)
.
Appendix 3: Calculation Details
Table S1
.
Components of free energies for all unsubstituted molecules along the
pathway (in kcal/mol unless otherwise specified)
Molecule
ZPE
Hvib
Svib
6kT
1/2
(Strans+Srot)
+ Selec
Selec
Htot
Stot
G(solv)
[Hartree]
E(SCF)
[Hartree]
G (total)
7
271.175
15.116
102.661
3.553
39.548
0.000
17.486
176.280
-
0.20755
-
1126.83365
-
706982.7
1
239.494
12.184
79.478
3.553
39.140
0.000
14.554
152.270
-
0.00357
-
994.59532
-
623901.5
3
248.555
12.674
79.408
3.553
39.187
0.000
15.044
158.720
-
0.05462
-
995.02012
-
624190.5
3X
248.418
12.664
79.186
3.553
39.156
0.000
15.034
158.510
-
0.05500
-
995.01916
-
624190.2
2
246.435
12.730
79.248
3.553
39.135
0.000
15.100
158.220
-
0.05666
-
995.00506
-
624184.4
TS 1a
376.896
19.088
121.859
3.553
40.208
0.000
21.458
204.500
-
0.05139
-
1287.25831
-
807449.0
TS 1b
377.273
19.001
120.540
3.553
40.384
0.000
21.371
202.470
-
0.05122
-
1287.26603
-
807453.1
TS 1c
376.360
19.180
123.272
3.553
40.152
0.000
21.550
204.450
-
0.05097
-
1287.28394
-
807465.7
TS 2
244.914
12.541
77.739
3.553
39.168
0.000
14.911
156.570
-
0.05438
-
994.97941
-
624168.1
6
250.655
12.905
83.564
3.553
39.116
0.000
15.275
156.310
-
0.21959
-
995.26462
-
624446.4
5
284.252
15.964
105.148
3.553
39.636
0.000
18.334
185.070
-
0.20638
-
1127.99198
-
707695.7
TS 4
318.273
17.361
114.003
3.553
40.058
0.000
19.731
196.430
-
0.19977
-
1243.70425
-
780269.5
TS 6
346.356
20.692
140.626
3.553
40.512
0.000
23.062
225.390
-
0.18950
-
1376.38954
-
863501.0
TS 3
316.096
17.607
116.413
3.553
40.020
0.000
19.977
198.730
-
0.19985
-
1243.72115
-
780282.8
TS 5
251.045
12.557
77.422
3.553
39.135
0.000
14.927
155.950
-
0.21917
-
995.22251
-
624417.8
Table S2.
Calculated Free energies
in kcal/mol.
Molecule
DeltaG
TS 1a
19.9
TS 1b
15.8
TS 1c
3.2
TS
2
15.2
3
-
7.3
2
-
1.1
3X
-
7.0
-
4.0
6
-
1.4
5
4.0
TS 4
20.6
1
TS 6
43.8
TS 3
7.3
TS 5
27.1
Table S3.
Free energy components for substituted complexes
(in kcal/mol unless otherwise specified)
Molecule
ZPE
Hvib
Svib
6kT
1/2
(Strans+Srot)
+ Selec
Selec
Htot
Stot
G(solv)
[Hartree]
E(SCF)
[Hartree]
G (total)
Methoxy
Rh1.MeO
280.29
15.56
102.96
3.55
40.11
0.00
17.93
177.97
-
0.00825
-
1223.58289
-
767559.5
Rh1.CpH.MeO
289.60
15.96
101.14
3.55
40.14
0.00
18.33
183.46
-
0.05285
-
1224.02261
-
767853.1
Rh3.H.MeO
287.47
16.03
101.48
3.55
40.09
0.00
18.40
183.23
-
0.05500
-
1224.00607
-
767846.2
NMe2
Rh1 NMe2
331.08
17.85
119.70
3.55
40.46
0.00
20.22
195.48
-
0.00820
-
1262.41238
-
791877.3
Rh1.CpH.NMe2
340.61
18.32
118.49
3.55
40.49
0.00
20.69
202.25
-
0.04792
-
1262.86760
-
792177.6
Rh3.H.Nme2b
338.52
18.40
118.84
3.55
40.44
0.00
20.77
201.70
-
0.05008
-
1262.85032
-
792170.2
DMPE
LBdmpe2
271.49
15.22
95.90
3.55
38.83
0.00
17.59
174.87
0.00152
-
1420.36858
-
891044.9
LBRh1.CpH.dmpe2
279.98
15.23
95.99
3.55
38.86
0.00
17.60
173.81
-
0.05405
-
1420.78920
-
891335.2
LBRh3.H.dmpe2
278.40
15.04
92.87
3.55
38.82
0.00
17.41
171.57
-
0.05588
-
1420.78746
-
891336.1
Table S4.
Calculated Free energies of substituted compounds
in kcal/mol
group
σ
π
Δ
G
Δ
E(SCF)
Protonation of
hydride
Protonation of Cp*
H
0
6.2
9.4
-
1.1
-
7.3
-
CF3
0.54
4.1
8.3
9.9
5.8
-
OCH3
-
0.27
6.9
10.4
-
5.0
-
11.9
-
NMe2
-
0.83
7.4
10.8
-
11.1
-
18.5
dmpe
1.13
-
0.9
1.1