COMMUNICATIONS
layer (3 cm) ofAl O3. The solution was concentrated to 2 mL and hexane
were performed using SHELXTL 5.1. CCDC-188268 (PPN-1) and
CCDC-188269 (2b) contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge via
Crystallographic Data Centre, 12, Union Road, Cambridge CB21EZ,
UK; fax: (þ 44)1223-336-033; or deposit@ccdc.cam.ac.uk).
[8] D. C. Liles, A. Shaver, E. Singleton, M. B. Wiege, J. Organomet. Chem.
1985, 288, C33.
[9] a) R. T. Baker, Inorg. Chem. 1986, 25, 109; b) R. L. Johnston, D. M. P.
Mingos, Inorg. Chem. 1986, 25, 3321; c) M. L. McKee, Z.-X. Wang,
P. v. R. Schleyer, J. Am. Chem. Soc. 2000, 122, 4781, and references
therein.
2
(20 mL) was added to precipitate the product as an orange-red air-stable
1
solid. Yield 38 mg (47%). H NMR (400.13 MHz, [D1]chloroform, 258C):
d ¼ ꢀ0.69 (bs, 2H; cage CH), 1.60 (s, 15H; C5Me5), 5.22 ppm (s, 5H; C5H5);
11B{1H} NMR (128.38 MHz, [D1]chloroform, 258C): d ¼ ꢀ5.26 (2B), 16.24
(2B), 17.92 (2B), 31.94 (1B), 38.31 (1B), 95.10 ppm (1B); elemental
analysis (%) calcd: C 38.17, H 5.84, B 18.19; found: C 38.16, H 5.89, B 18.11.
[(h-C5Me5)Ru(C2B9H11)Ru(h-C5Me5)] (2b): THF (4 mL) was added to a
mixture of[{( h-C5Me5)RuCl}4] (41 mg, 0.038 mmol) and Tl-1 (86 mg,
0.15 mmol). The reaction mixture was stirred for 4 h and filtered through a
thin layer (3 cm) ofAl 2O3. The solution was concentrated to 2 mL and
hexane (20 mL) was added to precipitate the product as a red air-stable
1
[10] K. Wade, Adv. Inorg. Chem. Radiochem. 1976, 18, 1.
[11] P. W. Fowler, Polyhedron 1985, 4, 2051.
solid. Yield 67 mg (74%). H NMR (400.13 MHz, [D1]chloroform, 258C):
d ¼ ꢀ1.27 (bs, 2H; cage CH), 1.59 ppm (s, 30H; C5Me5); 11B{1H} NMR
(128.38 MHz, [D1]chloroform, 258C): d ¼ ꢀ5.62 (2 B), 17.78 (4B), 36.37
(2B), 97.03 ppm (1B); elemental analysis (%) calcd: C 43.68, H 6.83, B
16.08; found: C 43.65, H 6.78, B 15.98.
Analogously, direct reaction of[{( h-C5Me5)RuCl}4] (82 mg, 0.075 mmol)
and Tl[Tl(C2B9H11)] (81 mg, 0.15 mmol) in THF or Me2CO gave 2b (64 mg,
70%).
Conformation-Dependent Ionization Energies
of l-Phenylalanine**
Complex 2b was also prepared in 55% yield starting from [(h-C5Me5)-
Ru(MeCN)3]CF3SO3, similar to preparation of 2a.
Received: July 9, 2002 [Z19691]
Kang Taek Lee, Jiha Sung, Kwang Jun Lee,
Young Dong Park, and Seong Keun Kim*
[1] R. N. Grimes in Comprehensive Organometallic Chemistry 1, Vol. 1
(Eds.: G. Wilkinson, F. G. A. Stone, E. W. Abel), Pergamon, New
York, 1982, p. 459.
In recent years there has been an outburst ofresearch
interest in small biological molecules in the gas phase.[1] By
placing these molecules on the ™transparent cover glass∫ ofan
isolated environment, one can unravel intrinsic properties
usually hidden in the complex medium ofa real biological
system. The need for such gas-phase studies arises from the
anticipation that many biological phenomena can be traced to
the fundamental properties of the molecular constituents.
Both laser spectroscopy and theoretical methods have made
great contributions to elucidating the structures and dynamics
ofnonrigid biomolecules and their solvated complexes in the
gas phase.[2]
Amino acids are known to exist in various conformations
resulting from the flexibility of their structures, which
comprise a backbone and a side chain or residue. The
conformational variety of amino acids plays a crucial role in
determining the three-dimensional structure ofproteins and
controlling their dynamics.[3] The energy barrier that separates
different conformers is typically rather small so that thermal
energy at room temperature enables the molecule to freely
change from one conformation to another. Therefore, it is not
generally feasible to isolate a specific conformer experimen-
tally at room temperature. By employing a supersonic
expansion, however, one can cool down the molecule to a
temperature low enough to isolate it in various frozen forms,
in other words, as individual conformers. Numerous exper-
[2] a) V. R. Miller, L. G. Sneddon, D. C. Beer, R. N. Grimes, J. Am. Chem.
Soc. 1974, 96, 3090; b) W. M. Maxwell, E. Sinn, R. N. Grimes, J. Am.
Chem. Soc. 1976, 98, 3490; c) M. Green, J. L. Spencer, F. G. A. Stone,
J. Chem. Soc. Daton Trans. 1979, 1679, and references therein;
d) G. K. Barker, M. P. Garcia, M. Green, F. G. A. Stone, A. J. Welch, J.
Chem. Soc. Chem. Commun. 1983, 137; e) M. P. Garcia, M. Green,
F. G. A. Stone, R. G. Somerville, A. J. Welch, C. E. Briant, D. N. Cox,
D. M. P. Mingos, J. Chem. Soc. Dalton Trans. 1985, 2343.
[3] An indirect insertion, based on two-electron reduction of closo-
carborane or metallacarborane with subsequent treatment of nido-
anion formed with a metal electrophile, is well known. For example:
a) D. F. Dustin, G. B. Dunks, M. F. Hawthorne, J. Am. Chem. Soc.
1973, 95, 1109; b) W. J. Evans, M. F. Hawthorne, Inorg. Chem. 1974,
13, 869.
[4] a) A. R. Kudinov, M. I. Rybinskaya, Yu. T. Struchkov, A. I. Yanovskii,
P. V. Petrovskii, J. Organomet. Chem. 1987, 336, 187; b) P. O. Lumme,
U. Turpeinen, A. R. Kudinov, M. I. Rybinskaya, Acta Crystallogr. Sect.
C 1990, 46, 1410.
[5] R. S. Coldicott, J. D. Kennedy, M. Thornton-Pett, J. Chem. Soc. Dalton
Trans. 1996, 3819.
[6] C. G. Salentine, M. F. Hawthorne, Inorg. Chem. 1978, 17, 1498.
[7] Crystallographic data for PPN-1: at 295 K crystals ofC 48H56B9NP2Ru
are monoclinic, space group P21/c, Z ¼ 4, a ¼ 16.800(3), b ¼ 16.044(3),
c ¼ 18.490(4) ä, b ¼ 109.152(5)8, V¼ 4707.7(15) ä3, m(MoKa) ¼
4.36 cmꢀ1. Intensities of26827 relfections were measured with a
Smart 1000 CCD diffractometer at 295 K (l(MoKa) ¼ 0.71073 ä, 2q <
508), and 8271 independent reflections (Rint ¼ 0.0603) were used in
further refinement. One of the two carbon atoms in the cage was
assumed to be disordered and occupied positions adjacent to either
side ofC(1). In the subsequent reifnements each ofthe disordered
atoms was assigned the scattering power ofan atom that was half
boron and halfcarbon. The refinement converged to wR2 ¼ 0.0973 and
GOF ¼ 0.992 for all independent reflections (R1 ¼ 0.0487 was calcu-
lated against F for 4518 observed reflections with I > 2s(I)). Crystallo-
graphic data for 2b: at 140 K crystals ofC 22H41B9Ru2 are monoclinic,
space group P21/n, Z ¼ 4, a ¼ 8.3431(13), b ¼ 15.782(3), c ¼
[*] Prof. Dr. S. K. Kim, K. T. Lee, J. Sung, K. J. Lee
School ofChemistry, Seoul National University
Seoul 151-747 (Korea)
Fax : (þ 82)2-889-5719
E-mail: seongkim@plaza.snu.ac.kr
20.446(3) ä, b ¼ 101.483(3)8, V¼ 2638.4(7) ä3, m(MoKa) ¼ 11.55 cmꢀ1
.
Prof. Dr. Y. D. Park
Department ofChemistry, Ajou University
Suwon, Kyunggi-do 442-749 (Korea)
Intensities of30997 relfections were measured with a Smart 1000
CCD diffractometer at 140 K (l(MoKa) ¼ 0.71073 ä, 2q < 608), and
7647 independent reflections (Rint ¼ 0.0325) were used in further
refinement. The refinement converged to wR2 ¼ 0.0981 and GOF ¼
1.040 for all independent reflections (R1 ¼ 0.0414 was calculated
against F for 6443 observed reflections with I > 2s(I)). All calculations
[**] This work was supported by the National Creative Research
Initiatives Program (99-C-CT-01-C-50) ofthe Ministry ofScience
and Technology ofKorea.
4114
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Angew. Chem. Int. Ed. 2002, 41, No. 21