A. Stone and E. Abel, Pergamon, New York, 1982, vol. 1, pp. 543–553;
Comprehensive Organometallic Chemistry II, ed. E. W. Abel, F. G. A.
Stone and G. Wilkinson, Pergamon, New York, 1995, vol. 1, pp.
257–273; A. K. Saxena, J. A. Maguire and N. S. Hosmane, Chem. Rev.,
1997, 97, 2421.
2 For references and reviews of carbaboranes, see: R. N. Grimes,
Carboranes, Academic Press, New York, 1970; Gmelin Handbook of
Inorganic Chemistry, Springer-Verlag, Berlin, FRG, 1974, Borverbin-
dungen 2, pp. 1–288; 1975, Borverbindungen 6, pp. 69–127; 1977,
Borverbindungen 11; 1977, Borverbindungen 12; T. Onak, Boron
Compounds, 1980, 1st suppl. vol. 3, pp. 206–247; T. Onak, Boron
Compounds, 1982, 2nd suppl. vol. 2, pp. 277–324; T. Onak, Boron
Compounds, 1988, 3rd suppl. vol. 4, pp. 153–254; T. Onak, Boron
Compounds, 1993, 4th suppl. vol. 4, pp. 178–321; T. Onak, in
Comprehensive Organometallic Chemistry, ed. G. Wilkinson, F. G. A.
Stone and E. W. Abel, Pergamon, New York, 1982, vol. 1, pp. 411–457;
Comprehensive Organometallic Chemistry II, ed. E. W. Abel, F. G. A.
Stone and G. Wilkinson, Pergamon, New York, 1995, vol. 1, pp.
Fig. 2 MP2/6-31G* optimised geometry of 2-tBu-1,2-PCB3H5 2. Selected
bond lengths (Å), P1–C2 2.04, P1–B3/5 1.99, P1–B4 1.93, C2–B3 1.54,
B3–B4 1.87.
B5H9.9,13,14 Fig. 2 shows the MP2/6-31G* (Gaussian9815)
optimised geometry of 2-tBu-1,2-PCB3H5 with the expected
square pyramidal nido-cluster; selected bond lengths are given.
The structural dimensions and bond angles associated with the
open face are virtually identical to those obtained for
1,2-C2B3H7, both computationally (optimisations at the MP2/
6-31G* level of theory) and from gas-phase electron diffraction
studies.9 The alternative isomer, 1-tBu-2,1-PCB3H5, is com-
puted to be only ca 2.3 kcal mol21 higher in energy compared
to 2. It is therefore possible that this species is formed in the
reaction reported here, but is not isolated experimentally.
Calculated shifts for MP2- (or DFT-) optimised geometries of
the four known nido-5-vertex compounds (1, 3–5)16 and larger
phosphacarbaboranes3,17 have so far resulted in good agreement
with their observed NMR shifts. Comparison between experi-
mental and theoretical15 (GIAO-B3LYP/6-311G*//MP2/
6-31G*) 11B, 1H and 31P NMR chemical shifts listed in Table 1
for 2-tBu-1,2-PCB3H5 2 show excellent agreement. At the same
levels of theory, P4 has a calculated peak shift of 2539 ppm,
which differs from the calculated 31P shift for 2 by only 17
ppm.
217–255; B. Stíbr, Chem. Rev., 1992, 92, 225.
˘
˘
3 T. Jelínek, D. Hynk, J. Holub and B. Stíbr, Inorg. Chem., 2001, 40,
4512; J. Holub, T. Jelínek, D. Hynk, Z. Plzák, I. Císarová, M.
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Bakardjiev and B. Stíbr, Chem. Eur. J., 2001, 7, 1546; J. Holub, D. L.
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Ormsby, J. D. Kennedy, R. Greatrex and B. Stíbr, Inorg. Chem.
Commun., 2000, 3, 178; D. Hong, S. E. Rathmill, D. E. Kadlecek and L.
G. Sneddon, Inorg. Chem., 2000, 39, 4996; A. M. Shedlow and L. G.
Sneddon, Inorg. Chem., 1998, 37, 5269; W. Keller, B. A. Barnum, J. W.
Bausch and L. G. Sneddon, Inorg. Chem., 1993, 32, 5058.
4 P. Paetzold, U. Englert, H. P. Hansen, F. Meyer and E. Leuschner, Z.
Anorg. Allg. Chem., 2001, 627, 498; P. Paetzold, Eur. J. Inorg. Chem.,
1998, 2, 143; U. Dörfler, D. L. Ormsby, R. Greatrex and J. D. Kennedy,
Inorg. Chim. Acta., 2000, 304, 268.
5 L. Wesemann, M. Trinkaus, Y. Ramjoie, B. Ganter, U. Englert and J.
Müller, Eur. J. Inorg. Chem., 2000, 4, 735.
6 D. A. Franz and R. N. Grimes, J. Am. Chem. Soc., 1970, 92, 1438; D. A.
Franz, V. R. Miller and R. N. Grimes, J. Am. Chem. Soc., 1972, 94,
412.
7 R. E. Williams, Inorg. Chem., 1971, 10, 210; R. E. Williams, Adv. Inorg.
Chem. Radiochem., 1976, 18, 66; K. Wade, Chem. Commun., 1971, 792;
K. Wade, Adv. Inorg. Chem. Radiochem., 1976, 18, 1.
8 M. Regitz and P. Binger, Angew. Chem., Int. Ed. Engl., 1988, 27,
1484.
9 M. A. Fox, R. Greatrex, A. Nikrahi, P. T. Brain, M. J. Picton, D. W. H.
Rankin, H. E. Robertson, M. Buhl, L. Li and R. A. Beaudet, Inorg.
Chem., 1998, 37, 2166.
Table 1 Observed and calculated 11B, 1H and 31P NMR chemical shifts for
2-tBu-1,2-PCB3H5
10 M. Kaupp, C. Aubauer, G. Engelhardt, T. M. Klapotke and O. L.
Malkina, J. Chem. Phys., 1999, 110, 3897.
Observed
Calculated
11 S. Masamune, M. Sakai, H. Ona and A. V. Kemp-Jones, J. Am. Chem.
Soc., 1972, 94, 8956.
12 V. I. Minkin, N. S. Zefirov, M. S. Korobov, N. V. Averina, A. M.
Boganov and L. E. Nivorozhkin, Zh. Org. Khim., 1981, 17, 2616.
13 P. v. R. Schleyer, J. Gauss, M. Bühl, R. Greatrex and M. A. Fox, J.
Chem. Soc., Chem. Commun., 1993, 1766.
14 R. Greatrex, N. N. Greenwood, D. W. H. Rankin and H. E. Robertson,
Polyhedron, 1987, 6, 1849; M. Bühl and P. v. R. Schleyer, J. Am. Chem.
Soc., 1992, 114, 477.
15 Gaussian 98, Revision A.9, M. J. Frisch, G. W. Trucks, H. B. Schlegel,
G. E. Scuseria, M. A. Robb, J. R. Cheeseman, V. G. Zakrzewski, J. A.
Montgomery, Jr., R. E. Stratmann, J. C. Burant, S. Dapprich, J. M.
Millam, A. D. Daniels, K. N. Kudin, M. C. Strain, O. Farkas, J. Tomasi,
V. Barone, M. Cossi, R. Cammi, B. Mennucci, C. Pomelli, C. Adamo,
S. Clifford, J. Ochterski, G. A. Petersson, P. Y. Ayala, Q. Cui, K.
Morokuma, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B.
Foresman, J. Cioslowski, J. V. Ortiz, A. G. Baboul, B. B. Stefanov, G.
Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. Gomperts, R. L. Martin,
D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, M.
Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong, J. L.
Andres, C. Gonzalez, M. Head-Gordon, E. S. Replogle and J. A. Pople,
Gaussian, Inc., Pittsburgh PA, 1998.
11B
B3,5
B4
1H
B(3,5)H
B(4)H
Me
28.1
211.6
222.0
219.4
2.89
2.28
1.00
3.03
2.72
1.11
m-H
22.88
22.83
31P
P1
2501
2522
The phosphaalkyne reaction described here is the only known
direct route to a phosphacarbaborane from a borane cluster. The
reaction of PCl3 with a nido- or arachno-carbaborane cluster
usually generates a phosphacarbaborane with a naked vertex
whereas, with RPCl2, a phosphacarbaborane with an RP vertex
is produced.3,18 As reactions of boranes and carbaboranes with
alkynes often produce carbaboranes,2 the parallel reactions of
these boranes and carbaboranes with P·CtBu may yield other
new phosphacarbaboranes. Interestingly, however, the reac-
tions between the borane adducts B10H12L2 (L = SMe2, NCMe)
and P·CtBu do not yield phosphacarbaboranes.19
16 G. K. S. Prakash, G. Rasul and G. A. Olah, J. Phys. Chem. A, 1998, 102,
2579.
˘
17 D. L. Ormsby, J. D. Kennedy, R. Greatrex and B. Stíbr, J. Organomet.
We thank the EPSRC for providing an Advanced Research
Fellowship to M. A. F., and Quota Awards to P. N. C. and D. L.
O.
Chem., 2000, 614–615, 61.
18 J. L. Little, J. T. Moran and L. J. Todd, J. Am. Chem. Soc., 1967, 89,
5495; L. J. Todd, J. L. Little and H. T. Silverstein, Inorg. Chem., 1969,
8, 1698; N. S. Hosmane, K. J. Lu, A. H. Cowley and M. A. Mordones,
Inorg. Chem., 1991, 30, 1325.
19 F. Meyer, P. Paetzold and U. Englert, Chem. Ber., 1994, 127, 93; R. W.
Miller and J. T. Spencer, Polyhedron, 1996, 15, 3151; R. W. Miller and
J. T. Spencer, Organometallics, 1996, 15, 4293.
Notes and references
1 For references and reviews of main group heteroboranes, see: L. J. Todd
in Comprehensive Organometallic Chemistry, ed., G. Wilkinson, F. G.
CHEM. COMMUN., 2002, 1448–1449
1449