Journal of Nuclear and Radiochemical Sciences, Vol. 6, No. 3, pp. 153-155, 2005

Synthesis, Structure, and Spectroscopic Properties of fac-[TcICl(CO) 3 (bpy)](bpy = 2,2'-bipyridine)
Yuji Tooyama,a Arinori Harano,b Takashi Yoshimura,*, a Tsutomu Takayama,b Tsutomu Sekine,bHiroshi Kudo,b and Atsushi ShinoharaaaDepartment of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Miyagi 980-8578, Japanb

Received: July 31, 2005; In Final Form: September 30, 2005
The 1:1 reaction of ((C2H5) 4N)2 [fac-TcCl3(CO)3] with 2,2'-bipyridine (bpy) gave fac-[TcCl(CO)3(bpy)] ([1]). Thecomplex [1] is characterized on the basis of electronic absorption and 1H NMR spectra along with single crystal
X-ray analysis. The complex [1] crystallizes in the orthorhombic space group Pca21 with a = 25.027(3) Å, b =6.5327(7) Å, c = 16.679(2) Å, V = 2726.9(6) Å, Z = 8, and R = 0.0320. In [1], Tc(I) ion is coordinated by threecarbonyls with the facial positions, one chloride, and one bpy ligand. The metal-to-ligand charge transfer transition band was observed at 354 nm in CH3CN solution. The transition energy of the metal-to-ligand charge transfer
band for [1] is somewhat larger than that for the Re congener.

1. Introduction
Since the discovery of an easily accessible preparation
method of six-coordinate octahedral technetium(I) complexes
with three carbonyl ligands, fac-Tc(CO)3 unit, the chemistry ofthe Tc(I) complexes has developed rapidly with respect to thesyntheses of the new complexes, besides their radiopharmaceuticals applications.1−6 It has been known that a number of thesecond- and third-row transition metal ions with a d6 low-spinground state, Mo(0),7 W(0), 8 Re(I),9 −11 Ru(II),12 Os(II),13Rh(III),14 and Ir(III)15, 16 having monodentate or polydentate
pyridyl ligands exhibit photoluminescence. For example therhenium tricarbonyl bipyridine complexes fac-[ReX(CO)3 (NN)] 0 or 1+ (X = halide, pyridine derivatives; N-N = α-diimine)show strong emission in the visible region at room temperature.9−11 The emission character has been assigned as metal-toligand charge transfer phosphorescence except for the π-π*transition of the several complexes.9−11 The rhenium tricarbonyl
α-diimine complexes have been shown the rich electrochemical and photochemical reactions.17
From the periodical low, it is expected that the iso-electronic
d6 low-spin Tc(I) complexes with polypyridine ligands have therich redox, photophysical and photochemical properties. Several
fac-TcI (CO)3 complexes containing α-diimine ligands such as
1,10-phenanthroline (phen) or 2,2'-bipyridine (bpy) have beensynthesized,18−21 however the information of their structures
and the spectroscopic properties is still limited. In this paper,
we report the synthesis, crystal structure, and spectroscopic
properties of fac-[TcI Cl(CO) 3 (bpy)] ([1]). The transitionenergy of the MLCT band in electronic absorption spectrum of
fac-[TcCl(CO)3(bpy)] in CH3CN was observed at shorter wavelength than that of fac-[ReCl(CO)3(bpy)].
2. Experimental Section
Preparation of the Complex. To a solution containing 0.055
g (0.10 mmol) of ((C2H5) 4N)2 [fac-TcCl3(CO)3] in 5 mL of acetonitrile was added a solution of 0.016 g (0.10 mmol) of 2,2'bipyridine in 5 mL of acetonitrile. The mixture was stirred for
2 h, which gave a yellow solution. The reaction solution was*Corresponding author. E-mail: tyoshi@chem.sci.osaka-u.ac.jp.
FAX: +81-6-6850-5418.

poured onto a silica-gel column (20 mm × 150 mm). The yellow band eluted with acetonitrile was collected, and then thesolution was evaporated to dryness. Recrystallization fromacetonitrile/n-pentane gave yellow microcrystals. Yield: 0.024
g (65%). Anal. Calcd for [TcCl(CO)3(bpy)]: C, 41.68; H, 2.15;
N, 7.48; Tc, 26.42%. Found: C, 41.22; H, 2.30; N, 7.17; Tc,26.72. 1H NMR in CD3CN; δ = 7.62 (dd, 2H), 8.15 (dd, 2H),
8.38 (d, 2H), 8.94 (d, 2H). IR (KBr, cm−1); 2030, 1927, 1906.
UV-vis in CH3CN, nm (ε /M−1cm−1) 354 (2770).
Physical Measurements. The electronic absorption spectrum
was recorded with JASCO V-550 UV/Vis spectrophotometer,
and the infrared spectrum was recorded with PERKIN-ELMER
983G spectrophotometer with KBr pellet at room temperature.
The 1H NMR spectrum was recorded with JEOL G5X270 in
CD3CN at the probe temperature. The residual proton signal of
the solvent molecule (δ = 1.93) was used as the reference. The
elemental analysis (C, H, N) were recorded with Yanaco MT-3
CHN recorder.
X-ray Crystal Structure Determinations. Single-crystal
X-ray diffraction experiment for [1] was performed on a Rigaku
Mercury CCD diffractometer with a graphite-monochromatized Mo Kα radiation (λ = 0.71070 Å). Crystallographic dataare summarized in Table 1. The structure was solved by direct
TABLE 1: Crystal Data for fac-[TcCl(CO) 3 (bpy)] ([1])
formulafw
crystal system
space groupa/Åb/Å
c/Å
V/Å3Z
T/K
λ /Å
dcalc /g cm−3
µ (Mo Kα)/cm−1
R (wR2)
GOF© 2005 The Japan Society of Nuclear and Radiochemical Sciences
Published on Web 12/28/2005

C13H8N2O3ClTc
372.67orthorhombic
Pca21
25.027(3)6.5327(7)16.679(2)2726.9(6)8173.2
0.71071.815
12.48
0.0320 (0.0730)
1.019

154 J. Nucl. Radiochem. Sci., Vol. 6, No. 3, 2005

Tooyamamethods and was refined by full-matrix least-squares techniques
using anisotropic thermal parameters for non-H atoms. All H
atoms were located at calculated positions. All calculations
were performed by using the teXsan crystallographic software
package.
3. Results and Discussion
Preparation of the Complex. Treatment of a colorless acetonitrile solution of ((C2H5) 4N) 2 [ fac-TcCl3 (CO)3] 6 with 1 molar
equivalent of bpy gave a yellow solution. The purification of thecomplex was succeeded by using silica-gel column chromatography eluted with acetonitrile. The elemental analytical result andthe radio activity measurement with a liquid scintillation counterare in good agreement with the formula [TcCl(CO) 3 (bpy)].
Characterization of the complex is performed on the basis of IR
and 1H NMR spectra, besides the X-ray crystallographic determination (vide supra). Previously, several fac-TcI (CO)3 complexes fac-[TcX(CO)3 (L-L)] (X = Cl, Br, I, L-L = phen18; X =Br,19 CH3CN,21 L-L = bpy) were synthesized by the reaction of[TcX(CO) 5] (X = Cl, Br, I, CH 3CN) with α-diimine ligands.
For example, fac-[Tc(CO) 3 (bpy)(CH3CN)] + was prepared by
the reaction of [Tc(CO) 5 (CH 3CN)] + with bpy in a 1:1 molar
ratio in refluxing CH3CN for 4h.21 It is noted that the synthetic
condition to produce fac-[TcCl(CO)3(bpy)] is much milder thanthat to synthesize fac-[Tc(CO)3(bpy)(acetonitrile)]+. The labile
nature of the chloride ions for fac-[TcCl3(CO)3] 2− is responsible
for the easier substitution on the technetium center.
Crystal Structure. X-ray structural analysis for [1] reveals
that two independent molecules exist, yet nearly identical. Oneof the complex molecules is shown in Figure 1, and selectedbond distances and angles of [1] are listed in Table 2. Three
CO ligands face a Tc octahedron and two nitrogen atoms of abpy ligand and one chlorine atom occupy the other coordinating sites of the technetium atom. The complex molecule has anapproximate Cs symmetry. The Tc atom adopts a slightly distorted octahedral geometry with C2-Tc1-N1 = 169.35(16), C3Tc1-N2 = 173.26(16), C15-Tc2-N3 = 173.27(15), C16-Tc2-N4 =173.72 (17), Cl1-Tc1-C1 = 177.97(14), and Cl2-Tc2-C14
178.32(13)˚. The bond angles of N1-Tc1-N2 and N3-Tc2-N4 are
75.25(12) and 75.35(12)˚, which are much smaller than 90˚ withthe angle of the regular octahedron, because of the bite angleof the chelating bpy ligand. The bond distances of Tc-C
1.906(4)-1.978(5) Å are in the ranges of the known TcI complexes containing Tc-CO bond.22 The Tc-N bond distances of[1] are 2.167(3)-2.187(3) Å. These values are ca. 0.1 Å longer
than those observed in the technetium polypyridine complexes,[TcIII (bpy) 3] 3+ (Tc-N = 2.077(10) Å) 23 and the Tc-N distance(2.075(6) Å) of the external nitrogen of the tpy ligand in Tc(I)complex [TcCl(tpy)(py) 2 ] (tpy = 2,2':6':2''-terpyridine, py =pyridine).24 This long Tc-N distance of [1] is due to the strong

Cl1C12C11C13O2C10C2C9C8N2Tc1

N1C3O3C7C6C1C4C5O1Figure 1. An ORTEP drawing of one of the two independent complex molecules of [1]. Hydrogen atoms are omitted for clarity.

TABLE 2: Selected Bond Distances(Å) and Angles (deg)for fac-[TcCl(CO) 3 (bpy)] ([1])
Distances
Tc1-C1
Tc1-C2
Tc1-C3
Tc1-N1
Tc1-N2
Tc1-Cl1
C1-O1
C2-O2
C3-O3

1.906(4)1.914(5)1.939(5)2.187(3)2.167(3)2.4958(10)1.138(5)1.143(6)1.133(5)

Tc2-C14
Tc2-C15
Tc2-C16
Tc2-N3
Tc2-N4
Tc2-Cl2
C14-O4
C15-O5C16-O6

1.978(5)1.911(4)1.918(5)2.178(3)2.174(3)2.4663(12)1.069(5)1.150(5)1.150(5)Angles
C1-Tc1-C2
C1-Tc1-C3
C2-Tc1-C3
C1-Tc1-N1
C1-Tc1-N2
C2-Tc1-N1
C2-Tc1-N2
C3-Tc1-N1
C3-Tc1-N2
N1-Tc1-N2
Cl1-Tc1-C1
Cl1-Tc1-C2
Cl1-Tc1-C3
Cl1-Tc1-N1
Cl1-Tc1-N2
Tc1-C1-O1
Tc1-C2-O2
Tc1-C3-O3

89.5(2)89.23(19)89.0(2)93.51(16)96.66(16)169.35(16)94.27(16)101.21(17)173.26(16)75.25(12)177.97(14)92.50(14)91.11(14)84.45(9)82.88(9)179.0(4)174.5(4)176.9(4)

C14-Tc2-C15
C14-Tc2-C16
C15-Tc2-C16
C14-Tc2-N3
C14-Tc2-N4
C15-Tc2-N3
C15-Tc2-N4
C16-Tc2-N3
C16-Tc2-N4
N3-Tc2-N4
Cl2-Tc2-C14
Cl2-Tc2-C15
Cl2-Tc2-C16
Cl2-Tc2-N3
Cl2-Tc2-N4
Tc2-C14-O4
Tc2-C15-O5
Tc2-C16-O6

88.84(17)88.02(18)87.94(18)93.41(15)93.40(15)173.27(15)98.20(14)98.47(16)173.72(17)75.35(12)178.32(13)92.11(13)93.40(15)85.48(9)85.09(9)172.9(4)178.7(4)179.0(5)trans influence of the Tc-C bonds. The Tc-Cl bond distances(2.4663(12) and 2.4958(10) Å) are somewhat shorter than thoseof [TcICl(tpy)(py) 2] (2.518 Å),24 however the values are similar
to that observed in [TcI Cl(CN-tBu) 2 (CO) 3 ] + (2.496(2) Å).22
Therefore, it can be said that the Tc-Cl distance in [1] is normal
as the trans position of the Tc-C bond of the carbonyl ligand.
Compared with the bond distances (Mn-C = 1.794(5) –1.812(4) Å, Mn-N = 2.044(3) – 2.062(3) Å, Mn-Cl = 2.399(1),2.404(1) Å) of the Mn congeners fac-[MnX(CO)3 (bpy)] (X =Cl, I), 25, 26 the bond distances around the Tc atom of [1] issomewhat larger than those of the Mn complexes. This difference is due to the difference of the ionic radii between Mn andTc ions. While the bond lengths and angles around the Tc atom
are very similar to the structurally characterized iso-electronicRe(I) tricarbonyl bipyridine complexes27−30 owing to the similarity of the ionic radii of Tc and Re ions.
Spectroscopic Properties. The 1H NMR spectrum of [1] inCD3CN at room temperature showed typical diamagnetic behavior and the only one set of the signals for bpy ligand wereobserved at 7.62, 8.15, 8.38, and 8.94 ppm. The positions of thesignals are shift to down field compared with the position of thesignals of free bpy ligand in CD3CN. This observation suggeststhat the complex retains the structure in CD3 CN. In the IRspectrum, three strong absorption peaks of the carbonyls andthe peaks from the bpy ligand were observed. The CO stretching bands are shown at 2030, 1927, and 1906 cm−1. The positions of the CO stretching peaks are similar to those of
fac-[TcBr(CO) 3 (bpy)] (2033, 1944, 1929 cm−1).19 This result
suggests that the structure of [1] is very similar to that of fac[TcBr(CO)3(bpy)]. In the UV-vis absorption spectrum for [1] inSynthesis, Structure, and Spectroscopic Properties

CH3CN, the band at 354 nm was observed. It is known that theband of MLCT transition (Re → π*bpy) for fac-[ReCl(CO)3(bpy)]
was shown at 371 nm.31 Thus, we assign the band at 354 nm for[1] as the metal-to-the ligand charge transfer from Tc to the π*
orbital of the bpy ligand. This band of [1] appears at somewhat
shorter wavelength than that of the Re analogue, fac[ReCl(CO)3(bpy)].
4. Conclusion
In the present study, the 1:1 reaction of fac-[TcCl3 (CO) 3 ]with 2,2'-bipyridine was found to give fac-[TcCl(CO)3(bpy)] ingood yield. The transition energy of the MLCT band for [1] issomewhat larger than that of fac-[ReCl(CO) 3 (bpy)] which is
known to give the strong MLCT emission in the visible region.
Because of the similarity of the structural and spectroscopic
properties between [1] and the Re analogue, it is expected that
fac-[TcCl(CO)3(bpy)] has the rich redox and photoluminescent
properties.
References(1) E. Palma, J. D. G. Correia, A. Domingos, I. Santos, R.
Alberto, and H. Spies, J. Organomet. Chem. 689, 4811
(2004).
(2) F. Zobi, B. Spingler, T. Fox, and R. Alberto, Inorg. Chem.
42, 2818 (2003).
(3) R. Alberto, K. Ortner, N. Wheatley, R. Schibli, and A. P.
Schubiger, J. Am. Chem. Soc. 123, 3135 (2001).
(4) R. Alberto, R. Schibli, A. P. Schubiger, U. Abram, H.-J.
Pietzsch, and B. Johannsen, J. Am. Chem. Soc. 121, 6076
(1999).
(5) R. Alberto, R. Schibli, D. Angst, P. A. Schubiger, U. Abram,
S. Abram, and T. A. Kaden, Transition Metal Chem. 22,597 (1997).
(6) R. Alberto, R. Schibli, P. A. Schubiger, U. Abram, and T.
A. Kaden, Polyhedron 15, 1079 (1996).
(7) R. M. Kolodziej and A. J. Lees, Organomet. 5, 450 (1986).
(8) A. J. Lees and A. W. Adamson, J. Am. Chem. Soc. 104, 3804
(1982).
(9) D. J. Stufkens and A. Velček, Jr., Coord. Chem. Rev. 177,127 (1998).
(10) K. S. Schanze, D. B. MacQueen, T. A. Perkins, and L. A.
Cabana, Coord. Chem. Rev. 122, 63 (1993).

J. Nucl. Radiochem. Sci., Vol. 6, No. 3, 2005 155(11) D. J. Stufkens, Comments on Inorg. Chem. 13, 359 (1992).
(12) A. Juris, V. Balzani, F. Barigelletti, S. Campagna, P. Belser,and A. Von Zelewsky, Coord. Chem. Rev. 84, 85 (1988).
(13) E. M. Kober, B. P. Sullivan, W. J. Dressick, J. V. Caspar, andT. J. Meyer, J. Am. Chem. Soc. 102, 7383 (1980).
(14) H. Yersin, W. Humbs, and J. Strasser, Coord. Chem. Rev.
159, 325 (1997).
(15) J.-P. Collin, I. M. Dixon, J.-P. Sauvage, J. A. G. Williams,F. Barigelletti, and L. Flamigni, J. Am. Chem. Soc. 121,5009 (1999).
(16) N. P. Ayala, C. M. Flynn, Jr., L. Sacksteder, J. N. Demas,and B. A. DeGraff, J. Am. Chem. Soc. 112, 3837 (1990).
(17) Y. Hayashi, S. Kita, B. S. Brunschwig, and E. Fujita, J.
Am. Chem. Soc. 125, 11976 (2003).
(18) W. Hieber, F. z. Lux, and C. Herget, Z. Naturforsch. B 20,1159 (1965).
(19) B. Lorenz, M. Findeisen, B. Olk, and K. Schmidt, Z. Anorg
Allgem. Chem. 566, 160 (1988).
(20) I. V. Borisova, A. E. Miroslavov, G. V. Sidorenko, and D.
N. Suglobov, Radiokhim. 33, 1 (1991).
(21) H. H. K. Castro, C. E. Hissink, J. H. Teuben, W. Vaalburg,and K. Panek, Recueil des Travaux Chimiques des Pays-Bas
111, 105 (1992).
(22) K. Schwochau, Technetium Chemistry and Radiopharmaceutical Applications. (Wiley-VCH, 2000).
(23) C. M. Archer, J. R. Dilworth, R. M. Thompson, M. McPartlin, D. C. Povey, and J. D. Kelly, J. Chem. Soc. Dalton Trans.
461 (1993).
(24) J. Barrera, A. K. Burrell, and J. C. Bryan, Inorg. Chem. 35,335 (1996).
(25) E. Horn, M. R. Snow, and E. R. T. Tiekink, Acta Crystallogr.
C43, 792 (1987).
(26) G. J. Stor, D. J. Stufkens, P. Vernooijs, E. J. Baerends, J.
Fraanje, and K. Goubitz, Inorg. Chem. 34, 1588 (1995).
(27) Y. D. Chen, L. Y. Zhang, and Z.-N. Chen, Acta Crystallogr.
E61, m121 (2005).
(28) Y. Chen, L. Zhang, and Z.-N. Chen, Acta Crystallogr. E59,
m429 (2003).
(29) P. Chen, M. Curry, and T. J. Meyer, Inorg. Chem. 28, 2271
(1989).
(30) V. W.-W. Yam, K. M.-C. Wong, and K.-K. Cheung, Organomet.
16, 1729 (1997).
(31) A. Velček, Jr., S. Záliš, J. Phys. Chem. A 109, 2991 (2005).