COMMUNICATIONS Angew. Chem. Int. Ed. 2001, 40, No. 10  WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001 1433-7851/01/4010-1867 $ 17.50+.50/0 1867 Experimental and Theoretical Observations of Aromaticity in Heterocyclic XAl 3  (X  Si, Ge, Sn, Pb) Systems** Xi Li, Hai-Feng Zhang, Lai-Sheng Wang,* Aleksey E. Kuznetsov, Nathan A. Cannon, and Alexander I. Boldyrev* The concept of aromaticity may seem foreign for metallic systems. After all, aromaticity usually refers to cyclic, planar, or conjugated organic molecules which possess (4n  2) p electrons and have a specific chemical and structural stability. Nevertheless, aromaticity has been extended to include Experimental Section 1: [(Cp* 2 ZrH 3 Li) 3 ] [19] (0.1 g, 0.27 mmol) was dissolved in THF (3 mL), PH 2 CH 2 CH 2 PH 2 (1.0 g, 10.87 mmol) was added dropwise to the stirred, colorless solution which became green, then aquamarine, and finally blue, over a period of 30 min. The reaction was stirred for 72 h, until it became colorless. Solvent was removed in vacuo, leaving a white solid which was dissolved in hexane, filtered, and placed in a freezer ( 35 8C). Colorless, X-ray quality crystals (0.86 g, 87 % yield) precipitated from solution, over 24 h. 1 H NMR (C 6 D 6 ): d  3.65 (dt, 2 H, 1 J P,H  330, 3 J H,H  10 Hz), 2.43 (m, 2H), 1.87 (m, 2H), 1.14 (m, 2H), 0.74 (m, 2H); 13 C{ 1 H} NMR (C 6 D 6 ): d  38.36, 30.66; 31 P NMR (C 6 D 6 ): d  22.5 (P 1 : 1 J P1,P1  237, 1 J P1,P0  186, 2 J P1,P0  20 Hz),  65.4 (P 0 : 1 J P1,P1  237, 1 J P1,P0  186, 2 J P1,P0  20 Hz) ; elemental analysis (%) calcd for P 4 C 4 H 10 : C 26.39, H 5.54; found: C 26.18, H 5.42. 2 : A 10 % by weight solution of [GaMe 3 ] in hexane (378 mg, 0.33 mmol) was added to a vial containing 1 (30 mg, 0.16 mmol), with stirring. A very fine white precipitate was evident in the clear colorless solution after 10 min. An aliquot of the reaction mixture was used immediately for 31 P NMR spectroscopic characterization. This compound rapidly degraded on standing. 31 P NMR (C 6 D 6 ): d  19.4 (m),  65.1 (m). 3 :A2 m hexane solution of [AlMe 3 ] (0.14 mL, 0.28 mmol) was quickly added to a stirred toluene (1 mL) solution of 1 (20 mg, 0.11 mmol). The reaction mixture was heated to 80 8C in a sealed reaction vessel for 1 week, during which time the solution turned a very pale orange. Solvent was removed in vacuo, and the resulting white solid was dissolved in a 1:1 mixture of THF and hexane, and placed in a freezer ( 35 8C) until clear, colorless, cubic crystals of 3 precipitated from solution in 64 % yield. 1 H NMR (C 7 D 8 ): d  2.3 (brs, 2H), 1.8 (brs, 2H), 1.2 (brs, 3H), 1.1 (brs, 2H), 0.8 (brs, 3H), 0.6 (brs, 2H),  0.2 (br s, 3 H),  0.3 (9 H),  0.7 (br s, 3H); 31 P NMR (C 6 D 6 ): d  1.9 (br m),  50.9 (br m),  67.1 (brm)  88.8 (br m); elemental analysis (%) calcd for C 11 H 29 P 4 Al 3 : C 36.08, H 7.98; found: C 35.88, H 7.78. Received: November 13, 2000 Revised: January 22, 2001 [Z 16094] [1] M. Baudler, Angew. Chem. 1987 , 99, 429 ; Angew. Chem. Int. Ed. Engl. 1987 , 26, 419. [2] O. J. Scherer, Angew. Chem. 1990, 102, 1137; Angew. Chem. Int. Ed. Engl. 1990, 29, 1104. [3] H.-G. von Schnering, W. von Hönle, Chem. Rev. 1988, 88, 242. [4] D. W. Stephan, Angew. Chem. 2000, 112, 322; Angew. Chem. Int. Ed. 2000, 39, 314. [5] M. Driess, J. Aust, K. Merz, C. VanWullen, Angew. Chem. 1999, 111, 3967; Angew. Chem. Int. Ed. 1999, 38, 3677. [6] C. von Hänisch, D. Fenske, Z. Anorg. Allg. Chem. 1998, 624, 367. [7] W. A. Herrmann, Angew. Chem. 1986, 98, 57; Angew. Chem. Int. Ed. Engl. 1986, 25, 56. [8] C. von Hänisch, D. Fenske, M. Kattannek, R. Ahlrichs, Angew. Chem. 1999, 111, 2900; Angew. Chem. Int. Ed. 1999, 38, 2736. [9] R. Ahlrichs, D. Fenske, H. Oesen, U. Schneider, Angew. Chem. 1992, 104, 312; Angew. Chem. Int. Ed. Engl. 1992, 31, 323. [10] J. Eisenmann, D. Fenske, F. Hezel, Z. Anorg. Allg. Chem. 1998, 624, 1095. [11] D. Fenske, H. Schottmüller, Z. Anorg. Allg. Chem. 1998, 624, 443. [12] M. Driess, S. Martin, K. Merz, V. Pintchouk, H. Pritzkow, H. Grützmacher, M. Kaupp, Angew. Chem. 1997 , 109, 1982; Angew. Chem. Int. Ed. Engl. 1997 , 36, 1894. [13] M. Driess, R. Gleiter, R. Janoschek, H. Pritzkow, M. Reisgys, Angew. Chem. 1994, 106, 1548; Angew. Chem. Int. Ed. Engl. 1994, 33, 1484. [14] M. Driess, M. Faulhaber, H. Pritzkow, Angew. Chem. 1997 , 109, 1980; Angew. Chem. Int. Ed. Engl. 1997 , 36, 1892. [15] M. Baudler, S. Esat, Chem. Ber. 1983, 116, 2711. [16] M. Baudler, M. Warnau, D. Koch, Chem. Ber. 1978, 111, 3838. [17] M. C. Fermin, D. W. Stephan, J. Am. Chem. Soc. 1995, 117 , 12 645. [18] N. Etkin, M. C. Fermin, D. W. Stephan, J. Am. Chem. Soc. 1997 , 119, 2954. [19] N. Etkin, A. J. Hoskin, D. W. Stephan, J. Am. Chem. Soc. 1997 , 119, 11 420. [20] Diffraction experiments were performed on a Siemens SMART System CCD diffractometer and solved with the SHELX-TL software package. Crystal data for 1: space group: P1 Å , a  6.6064(1), b  6.6258(2), c  10.6067(3) , a  80.624(2), b  74.3540(10), g  67.241(2)8, V  411.373(18)  3 , Z  2, data/parameters: 1331/81, R  0.0549, R w  0.1355, GOF  1.014. Crystal data for 3 : space group : C2/ c, a  26.7605(2), b  18.0602(3), c  23.085 (3) , b  98.04(1)8, V  11047.4(2)  3 , Z  8, data/parameters: 6497/326, R  0.0996, R w  0.2875, GOF  1.130. Crystallographic data (excluding structure factors) for the structures reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC-152132 and CCDC-152133. Copies of the data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: ( 44) 1223-336-033; e-mail: deposit@ccdc.cam.ac.uk). [*] Prof.Dr. L.-S. Wang, X. Li, H.-F. Zhang Department of Physics, Washington State University 2710 University Drive, Richland, WA 99352 (USA) and W. R. Wiley Environmental Molecular Sciences Laboratory Pacific Northwest National Laboratory, MS K8-88 P.O. Box 999, Richland, WA 99352 (USA) Fax: ( 1) 509-376-6066 E-mail: ls.wang@pnl.gov Prof. Dr. A. I. Boldyrev, A. E. Kuznetsov, N. A. Cannon Department of Chemistry and Biochemistry, Utah State University Logan, UT 84322 (USA) Fax: ( 1) 435-797-3390 E-mail : boldyrev@cc.usu.edu [**] The experimental work reported herein was supported by the National Science Foundation (DMR-0095828) and was performed at the W. R. Wiley Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the DOEs Office of Biological and Environmental Research and located at the Pacific Northwest National Laboratory, which is operated for DOE by the Battelle Memorial Institute. L.S.W. is an AlfredP. Sloan Foundation Research Fellow. The theoretical work was carried out at the Utah State University and was supported by the donors of The Petroleum Research Fund (ACS-PRF 35255-AC6), administered by the Amer- ican Chemical Society.