Synthesis and luminescence behaviour of mixed-metal rhenium(I)-copper(I) and -silver(I) alkynyl complexes. X-Ray crystal structures of [{η2-Re(CO)3(bpy)(C≡CPh)}2Cu]PF6 and [{η2-Re(CO)3(bpy)

Article abstract of DOI:10.1039/a902273b

Two mixed-metal rhenium(I)-copper(I) and -silver(I) alkynyl complexes, [{η²-Re(CO)₃(bpy)(C≡CPh)}₂Cu]PF₆ and [{η²-Re(CO)₃(bpy)(C≡CPh)}₂Ag]PF₆, have been synthesized and

Full text of DOI:10.1039/a902273b

Synthesis and luminescence behaviour of mixed-metal rhenium(i)–copper(i)
and –silver(i) alkynyl complexes. X-Ray crystal structures of
2
2
[{h -Re(CO)3(bpy)(C·CPh)}2Cu]PF6 and [{h -Re(CO)3(bpy)(C·CPh)}2Ag]PF6
Vivian Wing-Wah Yam,* Samuel Hung-Fai Chong, Keith Man-Chung Wong and Kung-Kai Cheung
Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong SAR, People’s Republic of
China. E-mail: wwyam@hkucc.hku.hk
Received (in Cambridge, UK) 22nd March 1999, Accepted 28th April 1999
Two mixed-metal rhenium(i)–copper(i) and –silver(i) alky-
absorption in the visible region is tentatively assigned as the
dp(Re) ? p (bpy) MLCT transition. The observation of the
2
*
nyl complexes, [{h -Re(CO)3(bpy)(C·CPh)}2Cu]PF6 1 and
2
[{h -Re(CO)3(bpy)(C·CPh)}2Ag]PF6 2, have been synthe-
sized and shown to exhibit rich luminescence behaviour; the
X-ray crystal structures of both complexes have also been
determined.
There has been a rapidly growing interest in the chemical and
2
physical properties of h -alkynyl-coordinated complexes.1,2
Organometallic substituted alkynes LnMC·CR3 exhibit a rich
coordination chemistry with copper(i), silver(i) and gold(i)
ions.2 To the best of our knowledge, luminescence studies of p-
bonded alkynyl complexes are rare2f despite numerous works
on the luminescence behaviour of the s-bonded counterparts
have been reported.4 With the recent reports on the successful
isolation of acetylide-bridged rhenium(i) organometal-
lics1a,2b,e,5 and our recent efforts in incorporating metal-to-
ligand charge transfer (MLCT) excited states into rhenium(i)
acetylide units to make luminescent rigid-rod materials,4d,6 we
have extended our interest to utilize the luminescent alkynyl
rhenium(i) complex, Re(CO)3(bpy)(C·CPh), to function as an
2
h -ligand towards CuI and AgI. Herein are reported the
synthesis, structure and luminescence behaviour of two mixed-
metal rhenium(i)–copper(i) and –silver(i) alkynyl complexes,
Fig. 1 Perspective drawing of the complex cation of 1 with atomic
numbering. Hydrogen atoms have been omitted for clarity. Thermal
ellipsoids were shown at the 40% probability level. Selected bond distances
(Å) and bond angles (°): Re(1)–C(4) 2.139(8), C(11)–C(5) 1.46(1), C(4)–
C(5) 1.23(1), C(4)–Cu(1) 1.997(8), C(5)–Cu(1) 2.093(8), C(6)–Cu(1)
2.076(8), C(7)–Cu(1) 2.004(7), C(6)–C(7) 1.20(1), C(17)–C(6) 1.47(1),
Re(2)–C(7) 2.143(8), C(5)–C(4)–Re(1) 171.3(7), C(4)–C(5)–C(11)
166.9(9), C(6)–C(7)–Re(2) 178.4(7), C(7)–C(6)–C(17) 164.9(8).
2
2
[{h -Re(CO)3(bpy)(C·CPh)}2Cu]PF6 1 and [{h -Re(CO)3-
(bpy)(C·CPh)}2Ag]PF6 2.
Reaction of Re(CO)3(bpy)(C·CPh)6c and [Cu(MeCN)4]PF6
in THF at room temperature in an inert atmosphere of nitrogen
2
for 0.5 h afforded [{h -Re(CO)3(bpy)(C·CPh)}2Cu]PF6 1,
which was isolated as yellow crystals after recrystallization
from dichloromethane–n-hexane. Similarly, reaction of Re-
(CO)3(bpy)(C·CPh) and [Ag(MeCN)4]PF6 in THF under
2
similar conditions afforded [{h -Re(CO)3(bpy)(C·CPh)}2-
Ag]PF6 2 as yellow crystals. The identities of both have been
1
confirmed by satisfactory H NMR spectroscopy, IR, positive
ESI-MS, elemental analyses,† and X-ray crystallography.‡
Figs. 1 and 2 depict perspective drawings of the complex
cations of 1 and 2, respectively, with atomic numbering. The
C·C bond lengths are in the range 1.20(1)–1.23(1) Å in 1 and
1.199(8)–1.203(8) Å in 2, which are slightly longer than that of
their precursor complex [Re(CO)3(bpy)(C·CPh)] of 1.199(9)
Å.6c The bend-back angles (C–C–R) at the coordinated triple
bond are 13.1(9)–18.2(9)° in 1 and 13.1(6)–14.4(6)° in 2 which
are also larger than that of their precursor complex [Re-
(CO)3(bpy)(C·CPh)] of 3.7(7)°.6c The interplanar angles be-
tween the MC·C planes are 98.7 and 96.0° in the two
independent molecules of 1 which is close to the expected 90°
for a tetrahedrally coordinated CuI atom, and 149.0° in 2. In
addition, the bond weakening observed by IR spectroscopy of
the C·C triple bonds in 1 and 2 relative to the precursor complex
(2083 cm21) further supports the p coordination mode of the
alkynyl group to the d10 metal centres.
Fig. 2 Perspective drawing of the complex cation of 2 with atomic
numbering. Hydrogen atoms have been omitted for clarity. Thermal
ellipsoids were shown at the 40% probability level. Selected bond distances
(Å) and bond angles (°): Re(1)–C(4) 2.159(6), C(11)–C(5) 1.444(8), C(4)–
C(5) 1.203(8), C(4)–Ag(1) 2.257(6), C(5)–Ag(1) 2.378(6), C(6)–Ag(1)
2.382(6), C(7)–Ag(1) 2.244(6), C(6)–C(7) 1.199(8), C(17)–C(6) 1.477(8),
Re(2)–C(7) 2.138(6), C(5)–C(4)–Re(1) 166.2(5), C(4)–C(5)–C(11)
166.9(6), C(6)–C(7)–Re(2) 165.9(5), C(7)–C(6)–C(17) 165.6(6).
The electronic absorption spectra of 1 and 2 both show an
intense absorption band at ca. 396 nm in dichloromethane
solution. With reference to previous spectroscopic work on
rhenium(i) diimine systems,4d,6,7 the intense low energy
Chem. Commun., 1999, 1013–1014
1013

‡ Crystal data for 1: [(C42H26N4O6CuRe2)+PF62·CH2Cl2], M = 1348.55,
triclinic, space group P1 (no. 2), a = 10.806(1), b = 17.408(2), c =
MLCT absorption band at higher energy than that found in the
related Re(CO)3(bpy)(C·CPh) precursor, which absorbs at ca.
420 nm in dichloromethane, is supportive of a lower-lying
dp(Re) orbital in 1 and 2, resulted from the weaker p-donating
ability of the acetylide ligand upon p-coordination to the d10
metal ions.
¯
25.199(2) Å, a = 81.432(7), b = 82.688(7), g = 88.139(7)°, V = 4648(1)
Å3, Z = 4, Dc = 1.927 g cm23, m(Mo-Ka) = 58.74 cm21, F(000) = 2576,
T
= 301 K. One crystallographic asymmetric unit consists of two
independent formula units. Convergence for 1111 variable parameters by
least-squares refinement on F with w = 4Fo2/s2(Fo2), where s2(Fo2) =
[s2(I) + (0.036Fo2)2] for 10761 reflections with I > 3s(I) was reached at
R = 0.032 and wR = 0.045 with a goodness-of-fit of 1.46. The F atoms in
both PF6 counter ions were refined isotropically.
Excitation of 1 and 2 both in the solid state and in fluid
solutions resulted in orange luminescence,† with emission
lifetimes of 0.18 and 0.16 ms in dichloromethane solutions,
For 2: [(C42H26N4O6AgRe2)+PF62·(CH3)2CO], M = 1366.02, triclinic,
3
respectively, which are attributed to the MLCT phosphores-
¯
space group P1 (no. 2), a = 11.485(1), b = 13.368(1), c = 17.259(1) Å, a
cence. Similar to the absorption studies, the close resemblance
of the MLCT emission energies of 1 and 2 is suggestive of the
similar s- and p-donating properties of the acetylide ligand
upon coordination to CuI and AgI. It is also interesting that both
1 and 2 emit at higher energies than their precursor complex, i.e.
the emission energies in CH2Cl2 follow the order: 1 (590 nm) 
= 102.048(6), b = 107.155(6), g = 103.476(6)°, V = 2549.8(10) Å3, Z =
2, Dc = 1.931 g cm23, m(Mo-Ka) = 56.63 cm21, F(000) = 1304, T = 301
K. Convergence for 575 variable parameters by least-squares refinement on
F with w = 4Fo2/s2(Fo2), where s2(Fo2) = [s2(I) + (0.024Fo2)2] for 5957
reflections with I > 3s(I) was reached at R = 0.026 and wR = 0.034 with
a goodness-of-fit of 1.33.
2 (600 nm)
>
Re(CO)3(bpy)(C·CPh) (654 nm).6c The
CCDC 182/1239. See http://www.rsc.org/suppdata/cc/1999/1013/ for
crystallographic files in .cif format.
observation of a blue shift in emission energies on going from
Re(CO)3(bpy)(C·CPh) to 1 and 2 is in line with the assignment
3
*
of a MLCT [dp(Re) ? p (bpy)] origin and disfavours the
1 (a) T. Weidmann, V. Weinrich, B. Wagner, C. Robl and W. Beck, Chem.
Ber., 1991, 124, 1363; (b) H. Werner, P. Bachmann, M. Laubender and
O. Gevert, Eur. J. Inorg. Chem., 1998, 1217; (c) V. Varga, J. Hiller, U.
Thewalt, M. Polasek and K. Mach, J. Organomet. Chem., 1998, 553, 15;
(d) B. E. Woodworth, P. S. White and J. L. Templeton, J. Am. Chem. Soc.,
1998, 120, 9028.
2 (a) O. M. Abu Salah and M. I. Bruce, J. Chem. Soc., Dalton Trans., 1974,
2302; (b) H. Lang, K. Kohler and S. Blau, Coord. Chem. Rev., 1995, 143,
113; (c) Y. Zhu, O. Clot, M. O. Wolf and G. P. A. Yap, J. Am. Chem. Soc.,
1998, 120, 1812; (d) C. Muller, J. A. Whiteford and P. J. Stang, J. Am.
Chem. Soc., 1998, 120, 9827; (e) S. Mihan, K. Sunkel and W. Beck,
Chem. Eur. J., 1999, 5, 745; (f) V. W. W. Yam, W. K. M. Fung and K. K.
Cheung, Angew. Chem., Int. Ed. Engl., 1996, 35, 1100.
assignment of a 3MLCT [dp(Re) ? p (C·CPh)] origin. Such a
*
trend can be rationalized by the fact that the acetylide ligand
would become a poorer electron donor upon coordination to CuI
or AgI, and as a result, the energy of the Re dp orbitals would be
lowered, leading to a higher 3MLCT emission energy.
V. W.-W. Y. acknowledges financial support from The
University of Hong Kong, S. H.-F. C. the receipt of a
postgraduate studentship, administered by The University of
Hong Kong, and K. M.-C. W. the receipt of a research
associateship supported by the Vice-Chancellor’s Development
Fund of The University of Hong Kong.
3 J. Manna, K. D. John and M. D. Hopkins, Adv. Organomet. Chem., 1995,
38, 79.
Notes and references
4 (a) V. W. W. Yam, S. W. K. Choi and K. K. Cheung, Organometallics,
1996, 15, 1734; (b) V. W. W. Yam, W. K. M. Fung and K. K. Cheung,
Chem. Commun., 1997, 963; (c) V. W. W. Yam, W. K. M. Fung, K. M. C.
Wong, V. C. Y. Lau and K. K. Cheung, Chem. Commun., 1998, 777;
(d) V. W. W. Yam, K. K. W. Lo and K. M. C. Wong, J. Organomet.
Chem., 1999, 578, 3.
† 1: 1H NMR (300 MHz, acetone-d6, 298 K, relative to SiMe4): d 6.80 (d,
2H, J 7.5 Hz, aryl H meta to ethynyl group), 7.15 (m, 3H, aryl H ortho and
para to ethynyl group), 7.70 (t, 2H, J 7.2 Hz, bpy H), 8.30 (t, 2H, J 7.8 Hz,
bpy H), 8.60 (d, 2H, J 8.2 Hz, bpy H), 9.15 (d, 2H, J 5.3 Hz, bpy H). IR
(Nujol mull, cm21): 2029, 1999, 1932, 1911 n(C·O, C·C). Positive ESI-
MS: ion cluster at m/z 1119 {M}+. UV–VIS [l/nm
(e/dm3 mol21 cm21)]: CH2Cl2, 246(28160), 288(29000), 396(6050). Emis-
sion [l/nm (to/ms)]: CH2Cl2 (298 K), 590 (0.18); solid (298 K), 550 (0.35);
solid (77 K), 540; EtOH–MeOH glass (4 :1 v/v) (77 K), 555. Found: C,
39.07, H, 2.07, N, 4.29. Calc. for 1·0.5CH2Cl2: C, 39.17; H, 1.94, N, 4.31%.
2: 1H NMR (300 MHz, acetone-d6, 298 K, relative to SiMe4): d 6.80 (d, 2H,
J 7.2 Hz, aryl H meta to ethynyl group), 7.10 (m, 3H, aryl H ortho and para
to ethynyl group), 7.60 (t, 2H, J 6.5 Hz, bpy H), 8.20 (t, 2H, J 7.4 Hz, bpy
H), 8.55 (d, 2H, J 8.1 Hz, bpy H), 9.0 (d, 2H, J 5.5 Hz, bpy H). IR (Nujol
mull, cm21): 2033, 2006, 1921, 1888 n(C·O, C·C). Positive ESI-MS: ion
cluster at m/z 1163 {M}+. UV–VIS [l/nm (e/dm3 mol21 cm21)]: CH2Cl2,
250(26890), 292(28240), 396(5930). Emission [l/nm (to/ms)]: CH2Cl2 (298
K), 600 (0.16); solid (298 K), 535 ( < 0.1); solid (77 K), 533; EtOH–MeOH
glass (4:1 v/v) (77 K), 540. Found: C, 38.53, H, 1.99, N, 4.28. Calc. for 2:
C, 38.44, H, 1.87, N, 4.26%.
5
(a) J. Heidrich, M. Steimann, M. Appel and W. Beck, Organometallics,
1990, 9, 1296; (b) U. H. F. Bunz, Angew. Chem., Int. Ed. Engl., 1996, 35,
969; (c) S. B. Falloon, W. Weng, A. M. Arif and J. A. Gladysz,
Organometallics, 1997, 16, 2008.
6 (a) V. W. W. Yam, V. C. Y. Lau and K. K. Cheung, Organometallics,
1995, 14, 2749; (b) V. W. W. Yam, V. C. Y. Lau and K. K. Cheung,
Organometallics, 1996, 15, 1740; (c) K. M. C. Wong, Ph.D Thesis, The
University of Hong Kong, 1998; (d) V. W. W. Yam, S. H. F. Chong and
K. K. Cheung, Chem. Commun., 1998, 2121.
7 (a) M. S. Wrighton and D. L. Morse, J. Am. Chem. Soc., 1974, 96, 998;
(b) G. Tapolsky, R. Duesing and T. J. Meyer, Inorg. Chem., 1990, 29,
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Communication 9/02273B
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Chem. Commun., 1999, 1013–1014