For comparison with the experimental values, we have also calculated these
same bond strength data using DFT with Tp
0 Rh(CNMe)(R)H as a model, with
methylisocyanide replacing neopentylisocyanide. A plot of calculated relative Rh–
C bond strengths vs. C–H bond strengths with these substrates also shows two
distinct linear correlations with slopes of 1.59 and 1.46 for the two analogous sets of
compounds (Fig. 4). While there is generally good agreement with the observed
experimental trends in Rh–C bond strengths, DFT overestimates the range of Rh–C
bond strengths by 10–15%.
Table 1 Kinetic and thermodynamic data for Tp
0 Rh(CNneopentyl)(R)H complexes
R
D(C–H)
a
ΔΔG oa
{
vs. PhH ΔG re
{
T re (R–H)
ΔG
0
vs. PhH #H D rel (M–C)
Ph112.9
0
30.95
296
0
6
0.0
t-Butylvinyl111.1
1.36
26.91
295
5.47
1
À6.2
Methyl105.0
0.70
23.52
296
8.17
4 À15.8
n-Pentyl100.2
0.79
22.43
296
9.35
6 À22.1
c-Pentyl95.6
1.78
21.18
296
11.59
10 À29.2
c-Hexyl99.5
1.80
21.40
296
11.39
12 À25.2
CF 3 CC135.4
a
0.75
30.10
373
À0.13
1
23.7
n-HexylCC131.0
a
1.19
30.39
373
0.02
1
19.1
Me 3 SiCC131.6
a
0.62
32.50
373
À2.66
1
22.4
Me 3 CCC131.4
a
0.96
30.83
373
À0.65
1
20.2
PhCC133.2
a
0.50
31.53
373
À1.81
1
23.2
p-CF 3 C 6 H 4 CC127.8
a
À0.09
31.83
373
À2.70
1
18.7
p-MeOC 6 H 4 CC122.7
a
0.29
30.78
373
À1.27
1
12.1
-C 2 H 4 CN
103.0
a
1.26
25.47
299
6.71
3 À16.2
-C 3 H 6 CN
101.3
a
1.17
23.64
299
8.45
3 À19.6
-C 4 H 8 CN
101.2
a
1.04
22.88
299
9.09
3 À20.4
-C 5 H 10 CN
101.2
a
1.04
22.38
299
9.58
3 À20.9
-CH 2 CN
94.8
1.48
31.36
373
À0.66
3 À17.0
-CH 2 C(Me)¼CH 2
89.1
0.74
23.92
296
7.81
6 À31.6
α-Mesityl89.4
0.13
24.49
296
6.63
9 À30.4
-CH 2 CCCH 3
90.7
0.44
26.98
340
3.44
6 À25.6
-CH 2 C(O)CH 3
96.0
0.73
27.71
340
3.00
6 À19.9
-CH 2 O
t Bu
93.0
0.84
25.43
340
5.39
3 À24.9
-CH 2 OCH 3
96.1
0.48
26.24
340
4.22
6 À21.0
-CH 2 F
101.3
0.81
28.48
340
2.31
3 À13.5
-CHF 2
103.2
2.33
30.36
373
1.19
2 À10.2
-CH 2 Cl
100.1
0.14
27.90
353
1.92
3 À14.3
-C 6 F 5
b
116.5
1.92
36.81
412
À6.57
1
11.2
-CH 2 CF 3
106.7
1.63
27.90
340
3.71
3
À9.5
Terminal C–H bond strengths in italics for alkynes and nitriles were calculated using DFT; B3LYP/
6-31G**
a
Energies are in kcal mol
À1
b
From Evans et al. [15]
76
W.D. Jones
same bond strength data using DFT with Tp
0 Rh(CNMe)(R)H as a model, with
methylisocyanide replacing neopentylisocyanide. A plot of calculated relative Rh–
C bond strengths vs. C–H bond strengths with these substrates also shows two
distinct linear correlations with slopes of 1.59 and 1.46 for the two analogous sets of
compounds (Fig. 4). While there is generally good agreement with the observed
experimental trends in Rh–C bond strengths, DFT overestimates the range of Rh–C
bond strengths by 10–15%.
Table 1 Kinetic and thermodynamic data for Tp
0 Rh(CNneopentyl)(R)H complexes
R
D(C–H)
a
ΔΔG oa
{
vs. PhH ΔG re
{
T re (R–H)
ΔG
0
vs. PhH #H D rel (M–C)
Ph112.9
0
30.95
296
0
6
0.0
t-Butylvinyl111.1
1.36
26.91
295
5.47
1
À6.2
Methyl105.0
0.70
23.52
296
8.17
4 À15.8
n-Pentyl100.2
0.79
22.43
296
9.35
6 À22.1
c-Pentyl95.6
1.78
21.18
296
11.59
10 À29.2
c-Hexyl99.5
1.80
21.40
296
11.39
12 À25.2
CF 3 CC135.4
a
0.75
30.10
373
À0.13
1
23.7
n-HexylCC131.0
a
1.19
30.39
373
0.02
1
19.1
Me 3 SiCC131.6
a
0.62
32.50
373
À2.66
1
22.4
Me 3 CCC131.4
a
0.96
30.83
373
À0.65
1
20.2
PhCC133.2
a
0.50
31.53
373
À1.81
1
23.2
p-CF 3 C 6 H 4 CC127.8
a
À0.09
31.83
373
À2.70
1
18.7
p-MeOC 6 H 4 CC122.7
a
0.29
30.78
373
À1.27
1
12.1
-C 2 H 4 CN
103.0
a
1.26
25.47
299
6.71
3 À16.2
-C 3 H 6 CN
101.3
a
1.17
23.64
299
8.45
3 À19.6
-C 4 H 8 CN
101.2
a
1.04
22.88
299
9.09
3 À20.4
-C 5 H 10 CN
101.2
a
1.04
22.38
299
9.58
3 À20.9
-CH 2 CN
94.8
1.48
31.36
373
À0.66
3 À17.0
-CH 2 C(Me)¼CH 2
89.1
0.74
23.92
296
7.81
6 À31.6
α-Mesityl89.4
0.13
24.49
296
6.63
9 À30.4
-CH 2 CCCH 3
90.7
0.44
26.98
340
3.44
6 À25.6
-CH 2 C(O)CH 3
96.0
0.73
27.71
340
3.00
6 À19.9
-CH 2 O
t Bu
93.0
0.84
25.43
340
5.39
3 À24.9
-CH 2 OCH 3
96.1
0.48
26.24
340
4.22
6 À21.0
-CH 2 F
101.3
0.81
28.48
340
2.31
3 À13.5
-CHF 2
103.2
2.33
30.36
373
1.19
2 À10.2
-CH 2 Cl
100.1
0.14
27.90
353
1.92
3 À14.3
-C 6 F 5
b
116.5
1.92
36.81
412
À6.57
1
11.2
-CH 2 CF 3
106.7
1.63
27.90
340
3.71
3
À9.5
Terminal C–H bond strengths in italics for alkynes and nitriles were calculated using DFT; B3LYP/
6-31G**
a
Energies are in kcal mol
À1
b
From Evans et al. [15]
76
W.D. Jones