Al 22 Cl 20 ‚12L (L ) THF, THP): The First Polyhedral Aluminum Chlorides Christoph Klemp, ² Michael Bruns, ‡ Ju 1 rgen Gauss, § Ulrich Ha 1 ussermann, | Gregor Sto 1 sser, ² Leo van Wu 1 llen, ⊥ Martin Jansen, ⊥ and Hansgeorg Schno 1 ckel* ,² Contribution from the Institut fu ¨ r Anorganische Chemie der UniVersita ¨ t Karlsruhe (TH), Engesserstrasse Gebaude 30.45, D-76128 Karlsruhe, Germany, Forschungszentrum Karlsruhe, Institut fu ¨ r Instrumentelle Analytik, Hermann-Von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany, Institut fu ¨ r Physikalische Chemie, UniVersita ¨ t Mainz, D-55099 Mainz, Germany, Inorganic Chemistry, Stockholm UniVersity, Stockholm, Sweden, and Max-Planck-Institut fu ¨ r Festko ¨ rperforschung, Stuttgart, Germany ReceiVed NoVember 20, 2000 Abstract: Aluminum subhalides of the type Al 22 X 20 ‚12L (X ) Cl, Br; L ) THF, THP) are the only known representatives of polyhedral aluminum subhalides and exhibit interesting multicenter bonding properties. Herein, we report on the synthesis and structural investigation of the first chlorides of this type. Additional investigations applying solid-state 27 Al NMR (MAS), XPS (of Al 4 Cp* 4 and Al 22 X 20 ‚12L), and quantum chemical calculations shed more light upon the structure of the molecules and possible Al modifications. Introduction Subhalides of all group XIII elements E n X m (E ) triels B, Al, Ga, In, Tl; X ) F, Cl, Br, I) are now well known. These compounds offer a great variety of structures which extend from the well-known saltlike Tl(I) halides to the molecular polyhedral boron subhalides such as, for example, B 4 X 4 and B 8 X 8 . 1 The subhalides of the elements Al, Ga, and In prefer the composition E n X n+2 with n ) 2, e.g., in compounds of the type L‚X 2 Es EX 2 ‚L (L ) donor). 2 Mixed-valent species, which were previ- ously known for the element boron, were recently also found for Al and Ga (n ) 3 or 5). 3 It even proved possible to isolate (oligomeric) monohalides of the E n X n type (E ) Al, Ga), i.e., Ga 8 I 8 ‚6NEt 3 and Al 4 X 4 ‚4L (X ) Br, I; L ) NEt 3 , PEt 3 ), 4 from donor-stabilized metastable EX solutions obtained by co- condensation. 5 Owing to the strong electron donors used, discrete 2e - -2c bonds are formed, thus yielding ring structures instead of E n X n polyhedra known from boron compounds. 6 Whereas no example of a polyhedral gallium subhalide is known, we have recently characterized the first polyhedral aluminum subhalide, namely, Al 22 Br 20 ‚12THF (1). 7 Herein, the first analogous chlorides Al 22 Cl 20 ‚12THF (2) and Al 22 Cl 20 ‚ 12THP (3) are described. The E n X n-2 -type species 1, 2, and 3 represent the first examples for metal-rich clusters of triel subhalides. 8 The properties of 2 and 3 were investigated using MAS and XPS. Experimental Section Synthesis of 2 and 3. Gaseous AlCl was continuously produced by the high-temperature reaction between liquid Al and gaseous HCl at 1000 °C and 10 -3 mbar. According to the established synthesis, 5 metastable AlCl solutions were generated by co-condensation of 40 mmol of AlCl together with 85 mL of toluene and 15 mL of either THF or THP. A 100-mL sample of donor-stabilized 0.4 M AlCl solutions is obtained in this way. Typically 10 mL of these dark red solutions was concentrated to half volume at room temperature, thereby removing the excess of donor solvent. Within several hours, small quantities of aluminum precipitated. After a few days, from the further concentrated filtrate pale yellow hexagonal plates of 2 respective to 3 crystallized. Yield: 47 mg (0.021 mmol, 11.5%) for 2 and 13 mg (0.054 mmol, 3%) for 3. The crystals were not soluble but decomposed on dissolution to yield AlX3 and further byproducts which were not yet characterized. They * Corresponding author: (fax) +49 (721) 608-4854; (e-mail) hg@ achpc9.chemie.uni-karlsruhe.de. ² Institut fu ¨r Anorganische Chemie der Universita ¨t Karlsruhe. ‡ Institut fu ¨r Instrumentelle Analytik. § Universita ¨t Mainz. | Stockholm University. ⊥ Max-Planck-Institut fu ¨r Festko ¨rperforschung. (1) (a) {B9X9}: Ho ¨nle, W.; Grin, Y.; Burkhardt, A.; Wedig, U.; Schultheiss, M.; Schnering, H. G. v.; Keller, R.; Binder, H. J. Solid State Chem. 1997, 133, 59. (b) {B6I6 - ,B6I6 2- }: Heinrich, A.; Keller, H.-L.; Preetz, W. Z. Naturforsch. B 1990, 45, 184. (2) (a) {Al2X4‚2L}: Ecker, A.; Friesen, M. A.; Junker, M. A.; U ¨ ffing, C.; Ko ¨ppe, R.; Schno ¨ckel, H. Z. Anorg. Allg. Chem. 1998, 624, 513. Mocker, M.; Robl, C.; Schno ¨ ckel, H. Angew. Chem. 1994, 106, 946; Angew. Chem., Int. Ed. Engl. 1994, 33, 862. (b) {Ga2X4‚2L}: Beagley, B.; Godfrey, S.; Kelly, K.; Kungwankunakorn, S.; McAuliffe, C.; Pritchard, R. Chem. Commun. 1996, 2179. Beamish, J. C.; Boardman, A.; Small, R. W. H.; Worrall, I. J. Polyhedron 1985, 4, 983. Beamish, J. C.; Small, R. W. H.; Worrall, I. J. Inorg. Chem. 1979, 18, 220. Small, R. W. H.; Worrall, I. J. Acta Crystallogr. 1982, 38b, 250. (3) (a) {Ga 3I5‚3PEt3}: Schnepf, A.; Doriat, C.; Mo ¨llhausen, E.; Schno ¨ck- el, H. Chem. Commun. 1997, 2111. (b) {Ga5Cl7‚5THF}: Loos, D.; Schno ¨ckel, H.; Fenske, D. Angew. Chem. 1993, 105, 1124; Angew. Chem., Int. Ed. Engl. 1993, 32, 1059. (c) {Al5Br7‚5THF}: Klemp, C.; Sto ¨sser, G.; Krossing, I.; Schno ¨ ckel, H. Angew. Chem. 2000, 112, 3834; Angew. Chem., Int. Ed. Engl. 2000, 39, 3691. (4) (a) {Ga8I8‚6NEt3}: Doriat, C.; Friesen, M.; Baum, E.; Ecker, A.; Schno ¨ckel, H. Angew. Chem. 1997, 109, 2057; Angew. Chem., Int. Ed. Engl. 1997, 36, 1969. (b) {Al4Br4‚4NEt3}: Mocker, M.; Robl, C.; Schno ¨ckel, H. Angew. Chem. 1994, 106, 1860; Angew. Chem., Int. Ed. Engl. 1994, 33, 1754. (c) {Al4I4‚4D}: Ecker, A.; Schno ¨ckel, H. Z. Anorg. Allg. Chem. 1998, 624, 813. (5) Dohmeier, C.; Loos, D.; Schno ¨ckel, H. Angew. Chem. 1996, 108, 141; Angew. Chem., Int. Ed. Engl. 1996, 35, 129. (6) For B 4X4 compounds, however, Libscomb postulated a planar tetrameric structure as an intermediate in the (“diamond-square-diamond”) isomerization of these compounds. 41a Furthermore, there also exist anionic polyhedral boron compounds like B12F12 2- . 41b (7) Klemp, C.; Ko ¨ppe, R.; Weckert, E.; Schno ¨ckel, H. Angew. Chem. 1999, 111, 1851; Angew. Chem., Int. Ed. Engl. 1999, 38, 1739. (8) To our knowledge, the Al22X20‚12L compound is in fact the only example at all of a neutral molecular icosahedral M12 cluster compound outside the boron chemistry. 9099 J. Am. Chem. Soc. 2001, 123, 9099-9106 10.1021/ja004022x CCC: $20.00 © 2001 American Chemical Society Published on Web 08/24/2001