Syntheses, Structures, and Electrochemical Properties of Os 3 (CO) 9-n (CNCH 2 Ph) n (μ 3 -η 2 :η 2 :η 2 -C 60 )(n ) 2-4) Chang Yeon Lee, ² Bo Keun Park, ² Jung Hee Yoon, ‡ Chang Seop Hong, ‡ and Joon T. Park* ,² Department of Chemistry and School of Molecular Science (BK21), Korea AdVanced Institute of Science and Technology, Daejeon 305-701, Korea, and Department of Chemistry and Center for Electro- and Photo-ResponsiVe Molecules, Korea UniVersity, Seoul, 136-701, Korea ReceiVed June 28, 2006 Benzyl isocyanide-substituted C 60 -triosmium complexes, Os 3 (CO) 9-n (CNCH 2 Ph) n (µ 3 -η 2 :η 2 :η 2 -C 60 )(n ) 2(3), 3 (4), and 4 (5)), have been prepared by reactions of either Os 3 (CO) 9 (µ 3 -η 2 :η 2 :η 2 -C 60 )(1) or its lesser isocyanide-substituted complexes with appropriate amounts of (triphenylphosphino)benzylimine (PhCH 2 NdPPh 3 ). Compounds 3-5 have been characterized by spectroscopic (IR, MS, 1 H and 13 C NMR) methods, cyclic voltammetry, and X-ray diffraction studies. Single-crystal X-ray diffraction studies reveal that isomer 3a has two inequivalent equatorial isocyanide ligands as a cis,trans-1,2-isomer and isomer 4a has three equivalent equatorial isocyanide ligands as a 1,2,3-isomer with C 3 symmetry. In compound 5, one benzyl isocyanide is axially coordinated to an osmium atom, whereas the other three benzyl isocyanide ligands are equatorially coordinated to each osmium atom. 1 H and 13 C NMR data, however, indicate that compound 3 exists as a mixture of 1,2- (3a) and 1,1-isomers (3b) in a ratio of 7:1, compound 4 as a mixture of 1,2,3- (4a) and 1,1,2-isomers (4b) in a ratio of 1:1, and compound 5, interestingly, as a single species of a 1,1,2,3-isomer in solution. The cyclic voltammetric studies reveal that all the CVs of 3-5 and related Os 3 (CO) 8 (CNCH 2 Ph)(µ 3 -η 2 :η 2 :η 2 -C 60 )(2) show four reversible redox waves that correspond to a one-electron process each with the third and fourth waves overlapped within the chlorobenzene solvent potential window. As more isocyanide ligands are coordinated in 2-5, all the corresponding half-wave potentials are gradually shifted to more negative potentials, reflecting the electron- donor property of the isocyanide ligand. Furthermore, C 60 -mediated electron delocalization from C 60 to the triosmium center takes place in the trianionic species of 2-5. The two isomers of 3 and 4 apparently undergo an equivalent electrochemical process, respectively. Introduction The interaction between metal clusters and a carbon cluster such as [60]fullerene (C 60 ) is one of the most interesting topics in the area of exohedral metallofullerene chemistry. 1 In par- ticular, we have been interested in C 60 -metal cluster complexes in order to investigate and understand the effects of metal cluster coordination on the chemical and physical properties of C 60 and the reactivities and electrochemical properties of these complexes 2a and ultimately to develop new electronic nanomaterials and nanodevices. 2b The C 60 -metal cluster complexes have been dominated by a π-type C 60 -metal cluster interaction with the µ 3 -η 2 :η 2 :η 2 -C 60 bonding mode. This unique π-bonding nature in C 60 -metal cluster complexes, surprisingly, results in both remarkable thermal stability and strong electronic communica- tion between C 60 and metal cluster centers. 2a Furthermore, this electronic communication can be fine-tuned with various ligands of different electronic properties coordinated on the metal cluster center. 2a We have also demonstrated that the µ 3 -η 2 :η 2 :η 2 -C 60 bonding mode can be modified by altering the coordination sphere of the metal centers to which C 60 is coordinated. 4c,d,6,9 This has led to continued and vigorous studies of C 60 -metal cluster chemistry, in which ligand substitution controls the fullerene tuning in terms of electrochemical properties and reactivities. This substitution chemistry is important in stabilizing * Corresponding author. E-mail: joontpark@kaist.ac.kr. Fax: + 82-42- 869-5826. ² KAIST. ‡ Korea University. (1) (a) Stephens, A.; Green, M. L. H. AdV. Inorg. Chem. 1997, 44,1-43. (b) Balch, A. L.; Olmstead, M. M. Chem. ReV. 1998, 98, 2123-2165. (c) Nakamura, E.; Isobe, H. Acc. Chem. Res. 2003, 36, 807-815. (2) (a) Lee, K.; Song, H.; Park, J. T. Acc. Chem. Res. 2003, 36, 78-86. (b) Cho, Y.-J.; Ahn, T. K.; Song, H.; Kim. K. S.; Lee, C. Y.; Seo, W. S.; Lee, K.; Kim, S. K.; Kim, D.; Park, J. T. J. Am. Chem. Soc. 2005, 127, 2380-2381. (3) Song, H.; Lee, Y.; Choi, Z.-H.; Lee, K.; Park, J. T.; Kwak, J.; Choi, M.-G. Organometallics 2001, 20, 3139-3144. (4) (a) Song, H.; Lee, K.; Park, J. T.; Choi, M.-G. Organometallics 1998, 17, 4477-4483. (b) Song, H.; Lee, K.; Park, J. T.; Chang, H. Y.; Choi, M.-G. J. Organomet. Chem. 2000, 599, 49-56. (c) Song, H.; Lee, K.; Choi, M.-G.; Park, J. T. Organometallics 2002, 21, 1756-1758. (d) Song, H.; Choi, J. I.; Lee, K.; Choi, M.-G.; Park, J. T. Organometallics 2002, 21, 5221-5228. (5) (a) Lee, K.; Hsu, H.-F.; Shapley, J. R. Organometallics 1997, 16, 3876-3877. (b) Lee, K.; Shapley, J. R. Organometallics 1998, 17, 3020- 3026. (c) Babcock, A. J.; Li, J.; Lee, K.; Shapley, J. R. Organometallics 2002, 21, 3940-3946. (6) (a) Lee, K.; Lee, C. H.; Song, H.; Park, J. T.; Chang, H. Y.; Choi, M.-G. Angew. Chem., Int. Ed. 2000, 39, 1801-1804. (b) Lee, K.; Choi, Z.-H.; Cho Y.-J.; Song, H.; Park, J. T. Organometallics 2001, 20, 5564- 5570. (7) (a) Lee, G.; Cho, Y.-J.; Park, B. K.; Lee, K.; Park, J. T. J. Am. Chem. Soc. 2003, 125, 13920-13921. (b) Park, B. K.; Miah, M. A.; Lee, G.; Cho, Y.-J.; Lee, K.; Park, S.; Choi, M,-G.; Park, J. T. Angew. Chem., Int. Ed. 2004, 43, 1712-1724. (c) Park, B. K.; Miah, M. A.; Kang, H.; Lee, K.; Cho, Y.-J.; Churchill, D. G.; Park, S.; Choi, M.-G.; Park, J. T. Organo- metallics 2005, 24, 675-679. (8) (a) Lee, K.; Song, H.; Kim, B.; Park, J. T.; Park, S.; Choi, M.-G. J. Am. Chem. Soc. 2002, 124, 2872-2873. (b) Lee, K.; Choi, Y. J.; Cho, Y.-J.; Lee, C. Y.; Song, H.; Lee, C. H.; Lee, Y. S.; Park, J. T. J. Am. Chem. Soc. 2004, 126, 9837-9844. (9) Song, H.; Lee, C. H.; Lee, K.; Park, J. T. Organometallics 2002, 21, 2514-2520. 4634 Organometallics 2006, 25, 4634-4642 10.1021/om060566h CCC: $33.50 © 2006 American Chemical Society Publication on Web 08/19/2006