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[Al(Al 3 R 3 ) 2 ]: Prototype of a Metalloid Al Cluster or a Sandwich‒Stabilized Al Atom?

2007; Wiley; Volume: 46; Issue: 19 Linguagem: Inglês

10.1002/anie.200604567

1521-3773

Ping Yang, Ralf Köppe, Taike Duan, Jens Hartig, Gunar Hadiprono, B. Pilawa, I. Keilhauer, Hansgeorg Schnöckel,

Boron and Carbon Nanomaterials Research

Angewandte Chemie International EditionVolume 46, Issue 19 p. 3579-3583 Communication [Al(Al3R3)2]: Prototype of a Metalloid Al Cluster or a Sandwich‒Stabilized Al Atom?† Ping Yang Dr., Ping Yang Dr. Department of Chemistry, Soochow University, 1 Shizi Street, Suzhou 215123, P.R. ChinaSearch for more papers by this authorRalf Köppe Dr., Ralf Köppe Dr. Institute of Inorganic Chemistry, University of Karlsruhe (TH), Engesserstrasse 15, Geb. 30.45, 76128 Karlsruhe, Germany, Fax: (+49) 721-608-4854Search for more papers by this authorTaike Duan Dr., Taike Duan Dr. Institute of Inorganic Chemistry, University of Karlsruhe (TH), Engesserstrasse 15, Geb. 30.45, 76128 Karlsruhe, Germany, Fax: (+49) 721-608-4854Search for more papers by this authorJens Hartig Dipl.-Chem., Jens Hartig Dipl.-Chem. Institute of Inorganic Chemistry, University of Karlsruhe (TH), Engesserstrasse 15, Geb. 30.45, 76128 Karlsruhe, Germany, Fax: (+49) 721-608-4854Search for more papers by this authorGunar Hadiprono Dr., Gunar Hadiprono Dr. Institute of Inorganic Chemistry, University of Karlsruhe (TH), Engesserstrasse 15, Geb. 30.45, 76128 Karlsruhe, Germany, Fax: (+49) 721-608-4854Search for more papers by this authorBernd Pilawa Priv.-Doz. Dr., Bernd Pilawa Priv.-Doz. Dr. Institute of Physics, University of Karlsruhe (TH), Wolfgang-Gaede-Strasse 1, 76128 Karlsruhe, GermanySearch for more papers by this authorIlka Keilhauer Dr., Ilka Keilhauer Dr. Institute of Physics, University of Karlsruhe (TH), Wolfgang-Gaede-Strasse 1, 76128 Karlsruhe, GermanySearch for more papers by this authorHansgeorg Schnöckel Prof. Dr., Hansgeorg Schnöckel Prof. Dr. [email protected] Institute of Inorganic Chemistry, University of Karlsruhe (TH), Engesserstrasse 15, Geb. 30.45, 76128 Karlsruhe, Germany, Fax: (+49) 721-608-4854Search for more papers by this author Ping Yang Dr., Ping Yang Dr. Department of Chemistry, Soochow University, 1 Shizi Street, Suzhou 215123, P.R. ChinaSearch for more papers by this authorRalf Köppe Dr., Ralf Köppe Dr. Institute of Inorganic Chemistry, University of Karlsruhe (TH), Engesserstrasse 15, Geb. 30.45, 76128 Karlsruhe, Germany, Fax: (+49) 721-608-4854Search for more papers by this authorTaike Duan Dr., Taike Duan Dr. Institute of Inorganic Chemistry, University of Karlsruhe (TH), Engesserstrasse 15, Geb. 30.45, 76128 Karlsruhe, Germany, Fax: (+49) 721-608-4854Search for more papers by this authorJens Hartig Dipl.-Chem., Jens Hartig Dipl.-Chem. Institute of Inorganic Chemistry, University of Karlsruhe (TH), Engesserstrasse 15, Geb. 30.45, 76128 Karlsruhe, Germany, Fax: (+49) 721-608-4854Search for more papers by this authorGunar Hadiprono Dr., Gunar Hadiprono Dr. Institute of Inorganic Chemistry, University of Karlsruhe (TH), Engesserstrasse 15, Geb. 30.45, 76128 Karlsruhe, Germany, Fax: (+49) 721-608-4854Search for more papers by this authorBernd Pilawa Priv.-Doz. Dr., Bernd Pilawa Priv.-Doz. Dr. Institute of Physics, University of Karlsruhe (TH), Wolfgang-Gaede-Strasse 1, 76128 Karlsruhe, GermanySearch for more papers by this authorIlka Keilhauer Dr., Ilka Keilhauer Dr. Institute of Physics, University of Karlsruhe (TH), Wolfgang-Gaede-Strasse 1, 76128 Karlsruhe, GermanySearch for more papers by this authorHansgeorg Schnöckel Prof. Dr., Hansgeorg Schnöckel Prof. Dr. [email protected] Institute of Inorganic Chemistry, University of Karlsruhe (TH), Engesserstrasse 15, Geb. 30.45, 76128 Karlsruhe, Germany, Fax: (+49) 721-608-4854Search for more papers by this author First published: 27 April 2007 https://doi.org/10.1002/anie.200604567Citations: 21 † This work was funded by the Deutsche Forschungsgemeinschaft (DFG), the Centre for Functional Nanostructures (CFN) at the University of Karlsruhe, and the Fonds der Chemischen Industrie. We thank P. Hauser und S. Schneider for the processing of the graphical material (including the title picture). P.Y. is grateful for a scholarship of the exchange program Baden-Württemberg-Jiangsu. R=N(SiMe2Ph)2. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Graphical Abstract Big Al: Nanometer-separated, perfectly arranged p1 spin systems are found in crystals of molecular [Al(Al3R3)2] radicals (R=N(SiMe2Ph)2; see spin-density diagram of the model compound [Al(AlNH2)6]). [Al(Al3R3)2] is surprisingly stable in the solid state. The unique topology of the seven metal atoms in the [Al(Al3R3)] molecules is discussed: Do these atoms represent a section of the bulk structure of Al and can thus be described as the simplest metalloid cluster? Supporting Information Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2007/z604567_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. References 1In accordance with the greek ειδoς (ideal, prototype), we have chosen the suffix -oid in the term "metalloid" to demonstrate that the topology of the metal atoms in such clusters is prototypical for that in the metals (elements). 2A. Purath, R. Köppe, H. Schnöckel, Angew. Chem. 1999, 111, 3114; Angew. Chem. Int. Ed. 1999, 38, 2926. 3 3aA. Schnepf, H. Schnöckel, Angew. Chem. 2002, 114, 3683; Angew. Chem. Int. Ed. 2002, 41, 3533; 3b"Clusters of the Heavier Group 13 Elements": G. Linti, H. Schnöckel W. Uhl, N. Wiberg in Molecular Clusters of the Main Group Elements, Wiley-VCH, Weinheim, 2004. 4H. Schnöckel, Dalton Trans. 2005, 3131. 5C. Dohmeier, H. Schnöckel, C. Robl, U. Schneider, R. Ahlrichs, Angew. Chem. 1993, 105, 1124; Angew. Chem. Int. Ed. Engl. 1993, 32, 1655. 6G. Hadiprono, Dissertation, Univ. Karlsruhe, 2005. 7C. Dohmeier, D. Loos, H. Schnöckel, Angew. Chem. 1996, 108, 141; Angew. Chem. Int. Ed. Engl. 1996, 35, 129. 8[Al7{N(SiMe2Ph)2}6]: Mr=1896.02 g mol−1, crystal dimensions: 0.5×0.5×0.5 mm3, trigonal, space group R, a=25.715(4), c=13.997(3) Å, V=8015(2) Å3, Z=3, ρcalcd=1.178 g cm−3, F(000)=3027.0, T=153(2) K, μ(MoKα)=0.71073 nm−1, 11 572 reflections, 3490 independent (Rint=0.0680), refined for F2 (θmax=26.02°), 271 parameters, 0 restraints, R1(I>2σ(I))=0.0466, wR2 (all data)=0.0973, GoF (F2)=1.012, ρ(min./max.)=−0.269/0.271 e Å−3; unit cell determination: 3490 reflections. Diffractometer: λ=0.7103 Å, Stoe-IPDS-II; Software: SHELXS-97, SHELXL-97, Stoe-IPDS-Software; structure refinement with direct methods, H atoms at calculated positions. CCDC-624700 (2) contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. 9In fullerides such as [C60]2−, despite having large cations (e.g. [Ni(NH3)6]2+),[12] the distances between the [C60]2−-ions are only about 10 Å in all directions (compared with 14 Å (2×), 15.6 Å (6×), and 17.5 Å (6×) for 2, see Figure 2). In fullerides, the HOMOs of individual C60 anions (diameter of about 7 Å) are nearly in close contact (i.e. the shortest intermolecular CC distances of 3.36 Å are of the same length as those in graphite), whereas, for example, the SOMOs of 2, by analogy to 2 a, are to a large extent localized in the {Al7} moieties and therefore separated from the electronic system of other clusters by the dielectric of the organic ligands. Consequently, the electronic interactions in 2 are expected to be significantly smaller than those in the fullerides. 10As 2 cannot be dissolved (e.g. in organic solvents) without decomposition, no EPR spectrum of the individual clusters could be obtained. 11Calculations were carried out with the TURBOMOLE program package. 11aR. Ahlrichs, M. Bär, M. Häser, H. Horn, C. Kölmel, Chem. Phys. Lett. 1989, 162, 165; 11bO. Treutler, R. Ahlrichs, J. Chem. Phys. 1995, 102, 346. DFT methods with the RI approximation and the BP-86 functional were applied; 11cK. Eichkorn, O. Treutler, H. Öhm, M. Häser, R. Ahlrichs, Chem. Phys. Lett. 1995, 240, 283; 11dA. D. Becke, Phys. Rev. B 1988, 38, 3098; 11eS. H. Vosko, L. Wilk, M. Nusair, Can. J. Phys. 1980, 58, 1200; 11fJ. P. Perdew, Phys. Rev. B 1986, 33, 8822. A split-valence-plus-polarization(SV(P)) basis set was used for all atoms; 11gA. Schäfer, H. Horn, R. Ahlrichs, J. Chem. Phys. 1992, 97, 2571. Partial charges were calculated according to the method by Roby and Davidson; 11hR. Heinzmann, R. Ahlrichs, Theor. Chim. Acta 1976, 42, 33; 11iR. Ahlrichs, C. Ehrhardt, Chem. Unserer Zeit 1985, 19, 120. NMR shifts and hyperfine coupling constants for the simulation of the EPR spectrum were calculated with the GAUSSIAN 03 program package; 11jGaussian 03 (Revision C.02): M. J. Frisch et al., see the Supporting Information. 12aK. Himmel, M. Jansen, Chem. Commun. 1998, 1205; 12bH. Brumm, M. Jansen, Z. Anorg. Allg. Chem. 2001, 627, 1433. 13The changes of bonds in the {Al7} framework can be ascribed to the following MOs: In 3+ binding contributions exist only for bonds to the central Al atom in the highest a1g and a2u orbitals. In contrast, for equivalent MOs of 3 a strengthening of bonds is expected for bonds to the central Al atom as well as inside the {Al3} rings. In 3− the HOMO (a2u) together with binding contributions of a high a1g MO is strongly binding concerning the {Al3} units. 14No significant differences result from a control calculation for the complete cluster ion 1 in comparison with 1 a (Table 1). 15In the discussion of the bonding situation in 1 and 2 the energetic relation to solid aluminum should be mentioned as a further aspect. Whereas the atomization of Al metal requires 326 kJ mol−1,[16] that is, the breaking of each of the 12 AlAl bonds requires 55 kJ mol−1, the sandwich stabilization of an Al atom by two {Al3R3} residues in the formation of 2 a provides 447 kJ mol−1, that is, 75 kJ mol−1 for each of the six AlAl bonds to the central Al atom. This strengthening of AlAl bonds in 2 a relative to the metal was expected because the higher coordination number of 12 in the metal results in a weakening of bonds. Moreover, the bond energy of 75 kJ mol−1 in 2 a has to be corrected to smaller values, as the bonds in the {Al3} rings are also enhanced in the formation of 2 a from an Al atom and {Al3R3} moieties, thus the bond energy of the AlAl bonds of 1 and 2 and that of Al metal are very similar in view of the factors mentioned. 16"NIST-JANAF Thermochemical Tables, Fourth Edition": 16aM. W. Chase, Jr., J. Phys. Chem. Ref. Data Monogr. 1989, 9; 16bNational Institute of Standards Web Based Chemical Data, http://webbook.nist.gov/chemistry/. 17 17aAll other 27Al resonances determined for 1 a and 2 a are in the same region at about 250 ppm and do not indicate an unusual bonding behavior of these atoms; 17bThe calculation of the 27Al NMR shifts for the complete cluster ion 1 tends to result in similar values (δ(Al1)=554 ppm; δ(Al2)=231 ppm). Furthermore, these results show that the choice of 1 a as a model compound is justified. 18P. L. Sagalyn, J. A. Hofmann, Phys. Rev. 1962, 127, 68. 19J. H. Ammeter, D. C. Schlosnagle, J. Chem. Phys. 1973, 59, 4784; R. Köppe, P. H. Kasai, J. Am. Chem. Soc. 1996, 118, 135. 20In this case, the distances between isolated Al atoms are of the same order of magnitude as those between the central Al atoms of individual clusters in the crystalline compound 2. 21R. J. Wright, M. Brynda, P. P. Power, Angew. Chem. 2006, 118, 6099. 22This is also indicated by the charge of −0.2 determined for the central Al atom in 3− (see Figure 4). The corresponding charges for 3+ and 3 are significantly more negative (−0.45 and −0.48, respectively). Negative charges in neutral metalloid clusters (e.g., [SiAl14Cp*6])[23] are not atypical. 23A. Purath, C. Dohmeier, A. Ecker, R. Köppe, H. Krautscheid, H. Schnöckel, R. Ahlrichs, C. Stoermer, J. Friedrich, P. Jutzi, J. Am. Chem. Soc. 2000, 122, 6955. 24Despite numerous attempts, the calculated 27Al NMR signal could not be experimentally verified. This negative result is, however, not unexpected, as only very rarely can 27Al NMR signals be detected for metalloid clusters. 25 25aH. D. B. Jenkins, J. F. Liebmann, Inorg. Chem. 2005, 44, 6359; 25bL. Glasser, H. D. B. Jenkins, Chem. Soc. Rev. 2005, 34, 866. 26Comparing these results should be simplified by the fact that both compounds crystallize in the same space group. 27The following theoretical (a) and spectroscopic (b) studies are planned or underway: a) As orientating band-structure calculations could not supply any indication for the presumed stronger interactions between cluster molecules of 2, detailed studies in cooperation with Prof. G. Seifert, TU Dresden, are currently being carried out, the results of which will be the topic of a future publication; b) Further EPR spectroscopic studies (also with pulsed methods) on single, preferably well-orientated, crystals are the aim of current experiments, which are, however, very time-consuming and experimentally difficult because crystals of 2 (like almost all metalloid Al and Ga clusters) are extremely air and moisture sensitive and can even ignite when exposed to air. Therefore, these crystals cannot easily be manipulated without contaminating or destroying them. However, these studies may assist in understanding the possibly unique magnetic interactions of the individual clusters of 2 in the collective. 28J. Frenzel, S. Gemming, G. Seifert, Phys. Rev. B 2004, 70, 235404. 29O. N. Bakharev, D. Bono, H. B. Brom, A. Schnepf, H. Schnöckel, L. J. de Jongh, Phys. Rev. Lett. 2006, 96, 117002. 30D. Bono, A. Schnepf, J. Hartig, A. Schnöckel, G. J. Nieuwenhuys, A. Amato, L. J. de Jongh, Phys. Rev. Lett. 2006, 97, 077601. 31J. Hartig, A. Schnepf, L. J. de Jongh, D. Bono, H. Schnöckel, Z. Anorg. Allg. Chem. 2007, 633, 63. Citing Literature Volume46, Issue19May 4, 2007Pages 3579-3583 ReferencesRelatedInformation