Extending Distannoxane Double Ladders Using Rigid Spacers: A Double Ladder with Eight Chiral Tin Atomssand a Twist! Dainis Dakternieks,* Andrew Duthie, and Bernhard Zobel Centre for Chiral and Molecular Technologies, Deakin University, Geelong, Victoria 3217, Australia Klaus Jurkschat* and Markus Schu ¨ rmann Lehrstuhl fu ¨ r Anorganische Chemie II der Universita ¨ t Dortmund, D-44221 Dortmund, Germany Edward R. T. Tiekink* ,† Department of Chemistry, University of Adelaide, South Australia 5005, Australia Received June 25, 2001 The new bulky silicon-containing ditin precursor p-(RCl 2 SnCH 2 SiMe 2 ) 2 C 6 H 4 (R ) CH 2 - SiMe 3 (4)) has been synthesized and further reacted to form a unique double ladder {[p- (R(Cl)SnCH 2 SiMe 2 ) 2 C 6 H 4 ]O} 4 (6). The two layers within 6 are twisted with respect to one another, resulting in a helical motif and a total absence of molecular symmetry so that there are eight chiral tin atoms within the system. The structure is compared to the double ladder {[m-(R(Cl)SnCH 2 CH 2 ) 2 C 6 H 4 ]O} 4 (11), which was prepared from the less sterically demanding ditin precursor m-(RCl 2 SnCH 2 CH 2 ) 2 C 6 H 4 (10). The two layers within 11 are parallel, and the molecule contains only two kinds of tin atom. Introduction Among the many and varied applications of organotin compounds, their use in catalysis continues to attract considerable attention. 1 In this context we have recently reported examples of double and triple ladders (A,R ) alkyl, X ) Cl, OAc; B,X ) Cl, R ) CH 2 SiMe 3 ). 2-4 Their structures are related to the well-known single ladders (distannoxanes) C (R ) alkyl, aryl, X ) range of anions), which are useful as mild Lewis acid catalysts in a variety of organic reactions. 5-18 Interestingly, distan- noxanes have not yet found utility in synthesis requiring chiral transformations, probably because no suitable chiral distannoxanes have yet been reported. Further- more, distannoxanes undergo extensive dissociation in solution, a property that also reduces their potential as chiral information transfer reagents. 19-23 By contrast, double and triple ladders undergo fewer dissociation reactions in solution, but, significantly, in these cases chiral information is retained at the tin centers. 4 A key motivation for our investigations has been the synthesis of new double ladders that have little or no symmetry as well as to increase the size of the interlayer region. 24 Such new molecular tin-oxo species hold considerable potential both for chiral catalysis and for genuine host- guest chemistry. † Present address: Department of Chemistry, National University of Singapore, Singapore 117543. (1) Beckmann, J.; Jurkschat, K.; Kaltenbrunner, U.; Rabe, S.; Schu ¨ rmann, M.; Dakternieks, D.; Duthie, A.; Mueller, D. Organome- tallics 2000, 19, 4887. (2) Dakternieks, D.; Jurkschat, K.; Schollmeyer, D.; Wu, H. Orga- nometallics 1994, 13, 4121. (3) Mehring, M.; Schu ¨ rmann, M.; Reuter, H.; Dakternieks, D.; Jurkschat, K. Angew. Chem., Int. Ed. Engl. 1997, 36, 1112. (4) (a) Mehring, M.; Schu ¨ rmann, M.; Paulus, I.; Horn, D.; Jurkschat, K.; Orita, A.; Otera, J.; Dakternieks, D.; Duthie, A. J. Organomet. Chem. 1999, 574, 176. (b) Mehring, M.; Paulus, I.; Zobel, B.; Schu ¨ r- mann, M.; Jurkschat, K.; Duthie, A.; Dakternieks, D. Eur. J. Inorg. Chem. 2001, 153. (5) Otera, J.; Yano, T.; Okawara, R. Organometallics 1986, 5, 1167. (6) Otera, J. Chem. Rev. 1993, 93, 1449. (7) Otera, J.; Ioka, S.; Nozaki, H. J. Org. Chem. 1989, 54, 4013. (8) Otera, J.; Yano, T.; Kawabata, A.; Nozaki, H. Tetrahedron Lett. 1986, 27, 2383. (9) Otera, J.; Dan-Oh, N.; Nozaki, H. J. Chem. Soc., Chem. Commun. 1991, 1742. (10) Otera, J.; Danoh, N.; Nozaki, H. J. Org. Chem. 1991, 56, 5307. (11) (a) Otera, J. In Advances in Detailed Reaction Mechanisms; Coxan, J. M., Ed.; JAI Press Inc.: London, 1994; Vol. 3, p 67. (b) Otera, J.; Danoh, N.; Nozaki, H. Tetrahedron 1992, 48, 1449. (12) Orita, A.; Mitsutome, A.; Otera, J. J. Org. Chem. 1998, 63, 2420. (13) Otera, J.; Yano, T.; Himeno, Y.; Nozaki, H. Tetrahedron Lett. 1986, 27, 4501. (14) Otera, J.; Nozak, H. Tetrahedron Lett. 1986, 27, 5743. (15) Otera, J.; Kawada, K.; Yano, T. Chem. Lett. 1996, 225. (16) Houghton, R. P.; Mulvaney, A. W. J. Organomet. Chem. 1996, 517, 107. (17) Houghton, R. P.; Mulvaney, A. W. J. Organomet. Chem. 1996, 518, 21. (18) Suciu, E. N.; Kuhlmann, B.; Knudsen, G. A.; Michaelson, R. C. J. Organomet. Chem. 1998, 556, 41. (19) Maeda, Y.; Okawara, R. J. Organomet. Chem. 1967, 10, 247. (20) Yano, T.; Nakashima, K.; Otera, J.; Okawara, R. Organome- tallics 1985, 4, 1501. (21) Gross, D. C. Inorg. Chem. 1989, 28, 2355. (22) Primel, O.; Llauro, M.-F.; Petiaud, R.; Michel, A. J. Organomet. Chem. 1998, 558, 19. (23) Dakternieks, D.; Jurkschat, K.; van Dreumel, S.; Tiekink, E. R. T. Inorg. Chem. 1997, 36, 2023. (24) Schulte, M.; Schu ¨ rmann, M.; Dakternieks, D.; Jurkschat, K. Chem. Commun. (Cambridge) 1999, 1291. 647 Organometallics 2002, 21, 647-652 10.1021/om0105627 CCC: $22.00 © 2002 American Chemical Society Publication on Web 01/24/2002