For 3b: C34H48B10Fe2, M = 676.52, triclinic, P ꢂ 1, a = 9.808(8),
b = 12.947(10), c = 14.060(11) A, a = 73.99(2), b = 78.525(15), g =
70.027(18)1, V = 1601(2) A3, Z = 2, Dc = 1.403 Mg mꢂ3, m =
0.933 mmꢂ1, F(000) = 708, ymax = 28.111. 7594/11459 reflections
(Rint = 0.0356), R1 = 0.0471, wR2 = 0.0984, S = 1.008, I 4 2s(I).
For 4a: C28H40B10Fe2, M = 596.40, monoclinic, P21/n, a =
8.7366(14), b = 16.920(3), c = 19.641(3) A, b = 100.783(7)1,
frequency, and as meta 3b converts to the even more distorted
ortho 4b the average shift is even greater, 6.5 ppm.
In conclusion, by utilising the fact that meta-carboranes can
be converted to ortho-carboranes by successive reduction and
reoxidation, we have prepared unprecedented, sterically-
V = 2852.1(8) A3, Z = 4, Dc = 1.389 Mg mꢂ3, m = 1.037 mmꢂ1
,
crowded, (2n
+ 2) skeletal electron ortho-carborane
derivatives which relieve that crowding by severe structural
deformation. We have previously proposed (derivatised)
sterically crowded metallacarboranes as potential vehicles by
which to study the mechanism(s) of isomerisation of
carboranes experimentally, a possibility which relies on the
ability of the crowded species to isomerise at relatively low
temperatures. However, results so far16 indicate only limited
agreement between theoretical predictions (on carboranes)
and experimental results (on metallacarboranes), possibly
linked to the greater electronic complexity of metalla-
carboranes. It may be that our ability now to prepare severely
crowded carboranes could revive interest in this area. In this
context it is informative to note that ortho-carborane 4b
converts to meta-carborane 3b in refluxing toluene.17
F(000) = 1240, ymax = 32.631. 9673/71 682 reflections (Rint = 0.0462),
R1 = 0.0323, wR2 = 0.0760, S = 1.034, I 4 2s(I).
For 4b: C34H48B10Fe2, M = 676.52, monoclinic, P21/n, a =
15.1029(17), b = 15.4587(19), c = 15.6930(18) A, b = 118.556(6)1,
V = 3218.2(7) A3, Z = 4, Dc = 1.396 Mg mꢂ3, m = 0.928 mmꢂ1
,
F(000) = 1416, ymax = 25.141. 5648/47 044 reflections (Rint = 0.0885),
R1 = 0.0492, wR2 = 0.1275, S = 1.053, I 4 2s(I).
z E.s.d.’s of the mean of N independent observations given by the
P
ꢀ 2
expression s2 = (s1 + s22) if N = 2, or s2 = { i=1 (w ꢂ w) }/
(N ꢂ 1) where wi is the ith and wꢀ the mean value if N 4 2.
8 Calculations run with Gaussian 03 with the BP86 functional and
6-31G** basis sets. See ESIw for full details.w
2
i=N
i
1 T. L. Heying, J. W. Ager, Jr, S. L. Clark, D. J. Mangold, H. L.
Goldstein, M. Hillman, R. J. Polak and J. W. Szymanski, Inorg.
Chem., 1963, 2, 1089.
2 M. G. Davidson, T. G. Hibbert, J. A. K. Howard, A. Mackinnon
and K. Wade, Chem. Commun., 1996, 2285.
We thank the EPSRC for support.
3 A. R. Turner, H. E. Robertson, K. B. Borisenko, D. W. H. Rankin
and M. A. Fox, Dalton Trans., 2005, 1310.
4 R. K. Bohn and M. D. Bohn, Inorg. Chem., 1971, 10, 350, and
references therein.
5 E.g. Y.-J. Lee, S.-J. Kim, C.-H. Kang, J. Ko, S. O. Kang and P. J.
Carroll, Organometallics, 1998, 17, 1109.
6 (a) E.g. F. Teixidor, C. Vinas, J. Rius, C. Miravitlles and J.
Notes and references
z Selected NMR spectroscopic data (CDCl3, 298 K): for 2a: 1H: Major
(b) isomer; d 6.42 (m, 1H, CH), 6.30 (m, 1H, CH), 6.23 (m, 1H, CH),
2.87 (m, 2H, CH2), 1.31* (s, 6H, CH3). Minor (a) isomer; d 6.62, 1H,
CH), 6.37 (m, 1H, CH), 6.05 (m, 1H, CH), 2.93 (m, 2H, CH2), 1.31*
(s, 6H, CH3). Relative integrals given are internal and the ratio of a : b
is 1 : 2. * = coincident resonance. 11B{1H}: d ꢂ6.4 (2B), ꢂ12.0 (6B),
ꢂ14.2 (2B), hd(11B)i ꢂ11.34.
Casabo, Inorg. Chem., 1990, 29, 149; (b) D.-H. Kim, J. Ko, K.
´
Park, S. Cho and S. O. Kang, Organometallics, 1999, 18, 2738.
7 (a) D. A. Brown, W. Clegg, H. M. Colquhoun, J. A. Daniels, I. R.
Stephenson and K. Wade, J. Chem. Soc., Chem. Commun., 1987,
889; (b) T. D. Getman, C. B. Knobler and M. F. Hawthorne, Inorg.
Chem., 1992, 31, 101; (c) K. Chui, H.-W. Li and Z. Xie, Organo-
metallics, 2000, 19, 5447; (d) L. A. Boyd, W. Clegg, R. C. B. Copley,
M. G. Davidson, M. A. Fox, T. G. Hibbert, J. A. K. Howard, A.
Mackinnon, R. J. Peace and K. Wade, Dalton Trans., 2004, 2786.
8 K. Wade, J. Chem. Soc. D, 1971, 792.
9 M. A. Fox, C. Nervi, A. Crivello and P. J. Low, Chem. Commun.,
2007, 2372.
10 J. M. Oliva, N. L. Allan, P. v. R. Schleyer, C. Vinas and F.
Teixidor, J. Am. Chem. Soc., 2005, 127, 13538.
11 E. Hong, Y. Kim and Y. Do, Organometallics, 1998, 17, 2933.
12 (a) G. B. Dunks, R. J. Wiersema and M. F. Hawthorne, J. Am. Chem.
Soc., 1973, 95, 3174; (b) L. I. Zakharkin, V. N. Kalinin and L. S.
Podvisotskaya, Bull. Acad. Sci. USSR, Div. Chem. Sci., 1966, 1444.
13 C. A. Brown and M. L. McKee, J. Mol. Model., 2006, 12, 653.
14 (a) E.g. Rh. Ll. Thomas and A. J. Welch, J. Chem. Soc., Dalton
Trans., 1997, 631; (b) F. Teixidor, C. Vinas, M. A. Flores, G. M.
Rosair, A. J. Welch and A. S. Weller, Inorg. Chem., 1998, 37, 5394.
15 (a) E.g. Z. G. Lewis and A. J. Welch, J. Organomet. Chem., 1992,
For 2b: 1H: Major (b) isomer; d 6.38 (m, 2H, CH), 6.03 (m, 1H,
CH), 2.98 (br m, 2H, CH2 [C5H5]), 2.08 (br d, 2H, CH2 [Pm]), 1.45 (br
m, 8H, CH2 [Pm]). Minor (a) isomer; d 6.47 (m, 1H, CH), 6.32 (m, 1H,
CH), 6.18 (m, 1H, CH), 2.83 (br m, 2H, CH2 [C5H5]), 1.90 (br d, 2H,
CH2 [Pm]), 1.03 (br m, 8H, CH2 [Pm]). Relative integrals given are
internal and the ratio of a : b is 2 : 9. 11B{1H}: d ꢂ6.6 (2B), ꢂ12.3 (6B),
ꢂ14.7 (2B), hd(11B)i ꢂ11.65.
1
For 3a: H: d 4.15 (m, 4H, C5H4), 4.10 (s, 10H, Cp), 4.01 (m, 4H,
C5H4), 1.38 (s, 12H, CH3). 11B{1H}: d ꢂ6.7 (2B), ꢂ12.2 (6B), ꢂ14.1
(2B), hd(11B)i ꢂ11.50.
For 3b: 1H: d 4.15 (m, 4H, C5H4), 4.07 (s, 10H, Cp), 3.98 (m, 4H,
C5H4), 2.17 (m, 4H, CH2), 1.90 (m, 8H, CH2), 1.59 (m, 6H, CH2), 1.37
(m, 2H, CH2). 11B{1H}: d ꢂ5.9 (2B), ꢂ12.4 (8B), hd(11B)i ꢂ11.12.
For 4a: 1H: d 4.24 (m, 4H, C5H4), 4.15 (m, 4H, C5H4), 4.12 (s, 10H,
Cp), 1.87 (s, 12H, CH3). 11B{1H}: d ꢂ2.6 (2B), ꢂ6.6 (4B), ꢂ7.9 (2B),
ꢂ12.6 (2B), hd(11B)i ꢂ7.25.
For 4b: 1H: d 4.23 (m, 4H, C5H4), 4.19 (m, 4H, C5H4), 4.11 (s, 10H,
Cp), 2.63 (m, 4H, CH2), 2.33 (m, 4H, CH2), 2.24 (m, 4H, CH2), 1.73
(m, 6H, CH2), 1.52 (m, 2H, CH2). 11B{1H}: d ꢂ0.7 (4B), ꢂ3.7 (4B),
ꢂ14.2 (2B), hd(11B)i ꢂ4.61.
430, C45; (b) P. T. Brain, M. Buhl, J. Cowie, Z. G. Lewis and A. J.
¨
Welch, J. Chem. Soc., Dalton Trans., 1996, 231; (c) A. J. Welch and
A. S. Weller, Inorg. Chem., 1996, 35, 4548; (d) A. J. Welch, Steric
Effects in Metallacarboranes, , in Metal Clusters in Chemistry, ed.
P. Braunstein, L. A. Oro and P. R. Raithby, Wiley-VCH,
Weinheim Germany, 1999, p. 26; (e) F. Teixidor, M. A. Flores,
y Crystal data: for 2a (mixture of a,a; b,b and a,b isomers): C18H32B10
,
M = 356.54, monoclinic, P2, a = 14.804(3), b = 10.428(3), c =
27.942(6) A, b = 100.501(15)1, V = 4241.3(17) A3, Z = 8, Dc
1.117 Mg mꢂ3, m = 0.055 mmꢂ1, F(000) = 1520. ymax = 24.691. 7586/
=
C. Vinas, R. Sillanpaa and R. Kivekas, J. Am. Chem. Soc., 2000,
¨
¨
¨
59 225 independent reflections (Rint = 0.1145), R1 = 0.0621, wR2
=
122, 1963; (f) A. V. Safronov, F. M. Dolgushin, P. V. Petrovskii
and I. T. Chizhevsky, Organometallics, 2005, 24, 2964; (g) L. S.
Alekseev, F. M. Dolgushin, A. A. Korlyukov, I. A. Godovikov, E.
V. Vorontsov and I. T. Chizhevsky, Organometallics, 2007, 26,
3868.
0.1403, S = 1.016 for data with I 4 2s(I).
For 2b: C24H40B10 (b,b isomer), M = 436.66, monoclinic, Cc, a =
21.315(4), b = 8.1515(16), c = 15.649(3) A, b = 112.03(3)1,
V = 2520.6(9) A3, Z = 4, Dc = 1.151 Mg mꢂ3, m = 0.058 mmꢂ1
,
F(000) = 936, ymax = 26.121. 2424/13998 reflections (Rint = 0.0399),
R1 = 0.0582, wR2 = 0.1515, S = 1.152, I 4 2s(I).
For 3a: C28H40B10Fe2, M = 596.40, triclinic, P ꢂ 1, a = 10.187(2),
b = 12.513(3), c = 13.387(2) A, a = 96.618(8), b = 112.070(7), g =
112.308(8)1, V = 1395.2(5) A3, Z = 2, Dc = 1.420 Mg mꢂ3, m =
1.060 mmꢂ1, F(000) = 620, ymax = 28.031. 6521/25611 reflections
(Rint = 0.0533), R1 = 0.0411, wR2 = 0.0893, S = 1.018, I 4 2s(I).
16 (a) E.g. S. Robertson, D. Ellis, G. M. Rosair and A. J. Welch, Appl.
Organomet. Chem., 2003, 17, 518; (b) S. Robertson, D. Ellis, G. M.
Rosair and A. J. Welch, J. Organomet. Chem., 2003, 680, 286; (c) S.
Robertson, R. M. Garrioch, D. Ellis, T. D. McGrath, B. E. Hodson,
G. M. Rosair and A. J. Welch, Inorg. Chim. Acta, 2005, 358, 1485.
17 B. W. Hutton and A. J. Welch, unpublished results.
ꢁc
This journal is The Royal Society of Chemistry 2008
Chem. Commun., 2008, 5345–5347 | 5347