Benzene rings iii and iv, immediately attached to the metal-
lacycle, are inclined to the latter plane by 50 and 66° (due to
steric overcrowding), while rings ii and v are inclined by only 10
and 22°, permitting p-electron conjugation along the ‘rod’.
Thus, in the metallacycle, the formally double bonds
C(15)NC(16) [1.382(6) Å] and C(17)NC(18) [1.389(6) Å] are
longer than in cyclopentadiene31 (1.344 Å) and its derivatives
d, J 8 Hz, PMe
3
trans to C), 1.38 (18H, vt, J 3 Hz, PMe
3 3
trans to PMe ), 0.42
(9H, s, TMS). Calc. for C50H P
64 3
RhSi: C, 68.65; H, 7.14. Found: C, 67.56;
21
H, 7.26%. IR (solid-state): n(C·C) 2160, 2128, 2021 cm
.
§
Crystal data for C50
64 3
H P RhSi 5: yellow prismatic crystal (0.46 3 0.09 3
0
.07 mm) grown by diffusion of hexane into a THF solution, M = 888.92,
orthorhombic, space group Pbca (no 61), a = 10.500(2), b = 19.180(1), c
3
21
=
47.927(6) Å, V = 9652(2) Å , Z = 8, m = 0.51 mm , T = 120 K,
32
SMART 1K CCD area detector, Mo-Ka radiation, 41968 reflections (7981
independent, R = 0.095), SHELXTL software (Bruker AXS, Madison,
WI, 1997), least squares refinement against F of all data, final R = 0.067
[5801 reflections with F
number 171634. See http://www.rsc.org/suppdata/cc/b1/b108625a/ for
crystallographic data in CIF or other electronic format.
(
average 1.341 Å). The C(16)–C(17) bond [1.465(6) Å] is
int
2
relatively short compared with non-conjugated, i.e. non-planar,
butadiene moieties32 (1.478 Å). The C(15)–C(19) and C(18)–
2
> 2s(F
2
)], wR(F ) = 0.112. CCDC reference
2
2
C(42) bonds [av. 1.415(7) Å] are short for a C(sp)–C(sp )
bond32 (1.431 Å). The alkyne bonds C(19)·C(20) and
C(42)·C(43) [av. 1.214(7) Å] are longer than the standard
value32 (1.181 Å) as well as the non-conjugated C(1)·C(2) bond
1
2
P. Nguyen, Z. Yuan, L. Agocs, G. Lesley and T. B. Marder, Inorg.
Chim. Acta, 1994, 220, 289.
M. S. Khan, A. K. Kakkar, N. J. Long, J. Lewis, P. Raithby, P. Nguyen,
T. B. Marder, F. Whittmann and R. H. Friend, J. Mater. Chem., 1994, 4,
[
1.167(7) Å]. Although each of these differences is on the
margin of statistical significance, they are all consistent with the
model of conjugation. The alkynyl ligand lies close to the
rhodacyclopentadiene plane, trans to the Rh–C(18) bond, which
is longer [2.110(5) Å] than the Rh–C(15) bond [2.087(5) Å] due
1
227.
3 P. Nguyen, G. Lesley, T. B. Marder, I. Ledoux and J. Zyss, Chem.
Mater., 1997, 9, 406.
4 C. Dai, P. Nguyen, T. B. Marder, A. J. Scott, W. Clegg and C. Viney,
Chem. Commun., 1999, 2493.
to the trans-influence. The SiMe
3
group and the P(1)Me
3
ligand
are rotationally disordered, each between two orientations in
5
6
U. H. F. Bunz, Chem. Rev., 2000, 100, 1605.
1
+1 and 3+1 ratios, respectively.
Z. L. Donhauser, B. A. Mantooth, K. F. Kelly, L. A. Bumm, J. D.
Monnell, J. J. Stapleton, D. W. Price, A. M. Rawlett, D. L. Allara, J. M.
Tour and P. S. Weiss, Science, 2001, 292, 2303.
The 31P{ H} NMR spectrum† of 5 displays a doublet of
1
doublets and a doublet of triplets consistent with a meridonal
III
(
3 3
PMe ) Rh coordination, where the unique phosphine is trans
7
S. M. Dirk, D. W. Price, S. Chanteau, D. V. Kosynkin and J. M. Tour,
Tetrahedron, 2001, 57, 5109.
1
1
to a Rh–C s-bond ( JRhP 82 Hz). The H NMR spectrum
indicated four non-equivalents p-tolyl groups, three meridonal
8 J. Kim and T. M. Swager, Nature, 2001, 411, 1030.
PMe
3
ligands and a SiMe
3
group. Thus, the solution NMR data
9 C. Schmitz, P. Posch, M. Thelakkat, H. W. Schmidt, A. Montak, K.
Feldman, P. Smith and C. Weder, Adv. Funct. Mater., 2001, 11, 41.
0 S. Lahiri, J. L. Thompson and J. S. Moore, J. Am. Chem. Soc., 2000, 122,
is entirely consistent with the solid-state structure.
1
1
1
1
The bright yellow compound 5 displays several intense
absorptions in the UV–VIS spectrum with peaks at 480 (e
1
1315.
1 M. Levitus, K. Schmieder, H. Ricks, K. D. Shimizu, U. H. F. Bunz and
M. A. Grace-Garibay, J. Am. Chem. Soc., 2001, 123, 4259.
2 H. Li, D. R. Powell, T. K. Firman and R. West, Macromolecules, 1998,
3
6 000), 452 (e = 43000), 434 (e = 31000), 333 (e = 36000)
3
21
21
and 312 nm (e = 55 000 dm mol cm ). We noted that NMR
samples of 5 in benzene or THF emitted green light when
exposed to ordinary fluorescent room lighting. An examination
of the luminescence spectra revealed that excitation at 452 nm
gave rise to emission bands at 500 and 532 nm (green), whereas
excitation at 333 nm showed these two bands as well as stronger
emissions at 366 and 384 nm. The absorption spectrum and the
emission spectrum resulting from 452 nm excitation are
remarkably similar in wavelength and extinction coefficients to
3
1, 1093.
3 P. Nguyen, S. Todd, D. v. d. Biggelaar, N. J. Taylor, T. B. Marder, F.
Wittmann and R. H. Friend, Synlett., 1994, 299.
14 T. Kawai, T. Saski and M. Irie, Chem. Commun., 2001, 711.
15 T. Shimura, A. Ohkubo, K. Aramaki, H. Uekusa, T. Fujita, S. Ohba and
H. Nishihara, Inorg. Chim. Acta, 1995, 230, 215.
1
1
1
6 T. Fujita, H. Uekusa, A. Ohkubo, T. Shimura, K. Aramaki, H. Nisihara
and S. Ohba, Acta Crystallogr., Sect. C, 1995, 51, 2265.
7 M. I. Bruce, N. N. Zaitseva, B. W. Skelton and A. H. White, Inorg.
Chim. Acta, 1996, 250, 129.
8 M. I. Bruce, B. W. Skelton, A. H. White and N. N. Zaitseva, J.
Organomet. Chem., 1998, 558, 197.
6 4
those observed previously for 9,10-bis(4-MeSC H C·C)an-
thracene.13 This is an exciting finding in light of the consider-
able current interest in luminescent organometallics,2,33,34
which may have applications as the emissive material in
OLEDs. Further photophysical studies on this and related
compounds are underway in order to elucidate the nature of the
states giving rise to the absorption and emission in 5.
19 S. P. Tunik, E. V. Grachova, U. R. Denisov, G. L. Starova, A. B.
Nikol’skii, F. M. Dolgushin, A. I. Yanovsky and Y. T. Struchkov, J.
Organomet. Chem., 1997, 536, 339.
2
0 A. A. Koridze, U. I. Zdanovich, N. V. Andrievskaga, Y. Siromakhova,
P. V. Petrovski, M. G. Ezernitskaya, F. M. Dolgushin, A. I. Yanovsky
and Y. T. Struchkov, Russ. Chem. Bull., 1996, 45, 1200.
1 U. Rosenthal, P.-M. Pellny, F. G. Kirchbauer and V. V. Burlakov, Acc.
Chem. Res., 2000, 33, 119.
We have prepared a rare example of a 2,5-bis(arylethy-
nyl)metallacyclopentadiene via the regiospecific reductive
coupling of two butadiynes at a rhodium centre. The highly
luminescent compound is formed in quantitative yield in
minutes at room temperature. Solid samples of 5 appear
relatively stable to the atmosphere, making this an attractive
system for further study and possible applications. The
compound offers exciting opportunities for functionalisation at
the metal bound alkynyl ligand, the phosphines, and the starting
diyne 1, as well as the possibility of changing the metal centre
from Rh to Co or Ir, all of which should allow tuning of the
luminescent properties of the system.
J. A. K. H. thanks EPSRC for a Senior Research Fellowship.
We thank Mr Simon FitzGerald and Dr Andrew Beeby for
assistance with the luminescence specta, Mrs J. Dostal for the
elemental analysis, Dr Dmitri S. Yufit for assistance with the
structural analysis and Dr Paul J. Low for many helpful
discussions and a preprint of ref. 23.
2
2
2 D. P. Hsu, W. M. Davis and S. L. Buchwald, J. Am. Chem. Soc., 1993,
1
15, 10394.
23 P. J. Low and M. I. Bruce, Adv. Organomet. Chem., 2001, 48, 71.
24 T. B. Marder, D. Zargarian, J. C. Calabrese, T. Herskovitz and D.
Milstein, Chem. Commun., 1987, 1484.
2
2
2
2
5 D. Zargarian, P. Chow, N. J. Taylor and T. B. Marder, J. Chem. Soc.,
Chem. Commun., 1989, 540.
6 P. Chow, D. Zargarian, N. J. Taylor and T. B. Marder, J. Chem. Soc.,
Chem. Commun., 1989, 1545.
7 H. B. Fyfe, M. Mlekuz, D. Zargarian, N. J. Taylor and T. B. Marder, J.
Chem. Soc., Chem. Commun., 1991, 188.
8 J. P. Rourke, D. W. Bruce and T. B. Marder, J. Chem. Soc., Dalton
Trans., 1995, 317.
29 J. P. Rourke, G. Stringer, P. Chow, R. J. Deeth, D. S. Yufit, J. A. K.
Howard and T. B. Marder, Organometallics, 2001, in press.
3
0 D. L. Thorn, Organometallics, 1985, 4, 192.
3
1 T. Haumann, J. Benet-Buchholz and R. Boese, J. Mol. Struct., 1996,
3
74, 299.
Notes and references
3
2 F. H. Allen, O. Kennard, D. G. Watson, L. Brammer, A. G. Orpen and
‡
2
(
7
(
NMR data: d
P
(80.96 MHz, C
D
6 6
) 28.81 (2P, dd, 1JRhP 99, 2JPP 30 Hz),
23.22 (1P, dt, JRhP 82, JPP 30 Hz). d (200.1 MHz, C ): 7.74 [2H,
AB)A, Ar], 7.43 [2H, (AB)A, Ar], 7.34 [2H, (AB)A, Ar], 7.23 [2H, (AB)A, Ar],
.06 [2H, (AB)A, Ar], 7.03 [2H, (AB)A, Ar], 6.99 [2H, (AB)A, Ar], 6.92 [2H,
AB)A, Ar], 2.08 (6H, s, Me), 2.03 (3H, s, Me), 2.01 (3H, s, Me), 1.77 (9H,
R. Taylor, J. Chem. Soc., Perkin Trans. 2, 1987, S1.
33 V. W.-W. Yam, Chem. Commun., 2001, 789.
34 S. Lamansky, P. J. Djurovish, D. Murphy, F. Abdel-Razzaq, H. E. Lee,
C. Adachi, P. E. Burrows, S. R. Forrest and M. E. Thompson, J. Am.
Chem. Soc., 2001, 123, 4304.
1
2
H
D
6 6
Chem. Commun., 2001, 2626–2627
2627