Communications Synthesis and Crystal Structure of a “Carbons Apart” Erbacarborane Sandwich: An Example of Novel, One-Pot, Two-Electron Reductive Cage Opening with Concomitant Metalation of the C 2 B 4 Carborane Ligand Jianhui Wang, †,‡ Shoujian Li, † Chong Zheng, † John A. Maguire, ‡ and Narayan S. Hosmane* ,† Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115-2862, and Department of Chemistry, Southern Methodist University, Dallas, Texas 75275 Received August 14, 2002 Summary: The reaction between 1,2-(SiMe 3 ) 2 -closo-1,2- C 2 B 4 H 4 (1), ErCl 3 , and K in a 2:1:4 molar ratio, in the absence of an outside electron-transfer agent, produced the erbacarborane sandwich 2,2′,4,4′-(SiMe 3 ) 4 -3,6′- [(µ-H) 2 K(THF) 2 ]-1,1′-commo-Er(η 5 -2,4-C 2 B 4 H 4 ) 2 (2) in 82% yield. All experimental observations are consistent with a process in which the erbium metal is acting as both the capping group and an electron-transfer agent. The two-electron reductive cage opening of closo- carboranes has been well-documented in the literature. 1 In a series of papers Stone and co-workers reported the simultaneous cage reduction and metalation of closo- carboranes in the C 2 B n (n ) 6, 8, 9) cage systems using a number of zerovalent nickel, platinum, and palladium complexes. 2 While the monocarbon carbaborane [closo- CB 10 H 11 ] - was also found to react in a similar manner, 3 the icosahedral closo-(RC) 2 B 10 H 10 cage has been opened by the reaction of a group 1 metal, in the presence and absence of catalysts, to give the corresponding nido- carboranes. 4,5 In addition, the group 2 element Mg was also found to react with closo-1,2-C 2 B 10 H 12 in the presence of catalytic amounts of 1,2-dibromomethane. 6 Nevertheless, Xie and co-workers have reported the uncatalyzed reduction of Na[1-(Me 2 C(C 5 H 5 )-closo-1,2- C 2 B 10 H 11 ] by Na metal to form the ansa ligand Na 3 [1-(Me 2 C(C 5 H 5 )-nido-1,2-C 2 B 10 H 11 ], in which a Cp - group is tethered to a dianionic nido-C 2 B 10 H 11 moiety * To whom correspondence should be addressed. E-mail: nhosmane@niu.edu. † Northern Illinois University. ‡ Southern Methodist University. (1) (a) Zakharkin, L. I.; Podvisotskaya, L. S. Zh. Obshch. Khim. 1967, 37, 506. (b) Zakharkin, L. I.; Kalinin, V. N.; Podvisotskaya, L. S. Izv. Akad. Nauk SSSR, Ser. Khim. 1967, 2310. (c) Stanko, V. I.; Goltyapin, Yu. V.; Brattsev, V. A. Zh. Obshch. Khim. 1969, 39, 1175. (d) Hosmane, N. S.; Jia, L.; Zhang, H.; Bausch, J. W.; Prakash, G. K. S.; Williams, R. E.; Onak, T. P. Inorg. Chem. 1991, 30, 3793-3795. (2) (a) Spencer, J. L.; Green, M.; Stone, F. G. A. J. Chem. Soc., Chem. Commun. 1972, 1178-1179. (b) Green, M.; Spencer, J. L.; Stone, F. G. A.; Welch, A. J. J. Chem. Soc., Dalton Trans. 1975, 179-184. (c) Green, M.; Spencer, J. L.; Stone, F. G. A. J. Chem. Soc., Dalton Trans. 1979, 1679-1686. (3) Carroll, W. E.; Green, M.; Stone, F. G. A.; Welch, A. J. J. Chem. Soc., Dalton Trans. 1975, 2263-2270. (4) (a) Dunks, G. B.; McKown, M. M.; Hawthorne, M. F. J. Am. Chem. Soc. 1971, 93, 2541-2543. (b) Getman, T. D.; Knobler, C. B.; Hawthorne, M. F. J. Am. Chem. Soc. 1990, 112, 4593-4594. (5) (a) Wilson, N. M. M.; Ellis, D.; Boyd, A. S. F.; Giles, B. T.; Macgregor, S. A.; Rosair, G. M.; Welch, A. J. Chem. Commun. 2002, 464-465. (b) Xie, Z.; Yan, C.; Yang, Q.; Mak, T. C. W. Angew. Chem., Int. Ed. 1999, 38, 1761-1763. (c) Chui, K.; Li, H.-W.; Xie, Z. Organo- metallics 2000, 19, 5447-5453. (d) Zi, G.; Li, H.-W.; Xie, Z. Chem. Commun. 2001, 1110-1111. (6) Vin ˜ as, C.; Barbera ` , G.; Teixidor, F. J. Organomet. Chem. 2002, 642, 16-19. Volume 21, Number 24, November 25, 2002 © Copyright 2002 American Chemical Society 10.1021/om020663k CCC: $22.00 © 2002 American Chemical Society Publication on Web 10/26/2002