Doubly Charged Four-Membered Ring Systems: Cyclobutadiene Dianions and Heavy Cyclobutadiene Dianions

Akira Sekiguchi; Tsukasa Matsuo

doi:10.1055/s-2006-950280

ACCOUNT

Doubly Charged Four-Membered Ring Systems: Cyclobutadiene Dianions and Heavy Cyclobutadiene Dianions

Akira Sekiguchi*^a, Tsukasa Matsuo^b
^a Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan
Fax: +81(298)534314; e-Mail: sekiguch@staff.chem.tsukuba.ac.jp;
^b Coordination Chemistry Laboratories, Institute for Molecular Science, Okazaki, Aichi, 444-8787, Japan
Fax: +81(564)595589; e-Mail: tmatsu@ims.ac.jp;

Abstract

All articles of this category

Abstract

Recent progress in the experimental chemistry of cyclobutadiene dianions (CBD^2-s) containing a doubly charged four-membered ring system is reviewed. New families of silyl-substituted CBD^2-s, cyclobutadienes (CBDs), and tetrahedranes are covered in detail. The aromaticity of the tetrasilyl- and diphenyldisilyl-CBD^2-s have been studied on the basis of structural characteristics and magnetic properties. All of the CBD^2-s show a strong diatropic ring current resulting from six π-electron system. The preparation of CBD^2- derivatives consisting of heavier group 14 elements (Si and Ge) is also included. They demonstrate a non-aromatic nature with a folded four-membered ring.

1 Introduction
2 Cyclobutadiene Dianions (CBD^2-s)
2.1 Preparation of CBD Complexes
2.2 Transmetalation of CBD Complexes
2.3 Tetrasilyl-CBD^2-s
2.4 Diphenyl-Disilyl-CBD^2-s
3 Cyclobutadienes (CBDs)
4 Tetrahedranes
5 Heavy Cyclobutadiene Dianions (CBD^2-s)
6 Conclusion

Key words

silicon - small-ring systems - cyclobutadiene dianions - cyclobutadienes - tetrahedranes - aromaticity - cage compounds - germanium

Full Text

References

<A NAME="RA41206ST-1">1</A> Sekiguchi A. Matsuo T. Watanabe H. J. Am. Chem. Soc. 2000, 122: 5652

<A NAME="RA41206ST-2A">2a</A> Binsch G. Naturwissenschaften 1973, 60: 369

<A NAME="RA41206ST-2B">2b</A> Bally T. Masamune S. Tetrahedron 1980, 36: 343

<A NAME="RA41206ST-2C">2c</A> Garratt P. Aromaticity Wiley; New York: 1986.

<A NAME="RA41206ST-2D">2d</A> Toda F. Garratt P. Chem. Rev. 1992, 92: 1685

<A NAME="RA41206ST-2E">2e</A> Minkin VL. Glukhovtsev MN. Simkin BY. Aromaticity and Antiaromaticity Wiley; New York: 1994.

<A NAME="RA41206ST-2F">2f</A> Bertrand G. Angew. Chem. Int. Ed. 1998, 37: 270

A thematic issue of aromaticity, edited by von Ragué Schleyer, P., has been published: Chem. Rev. 2001, 101, 1115-1566.

<A NAME="RA41206ST-4A">4a</A> McKennis JS. Brener L. Schweiger JR. Pettit R. J. Chem. Soc., Chem. Commun. 1972, 365

<A NAME="RA41206ST-4B">4b</A> Garratt PJ. Zahler R. J. Am. Chem. Soc. 1978, 100: 7753

<A NAME="RA41206ST-4C">4c</A> Boche G. Etzrodt H. Marsch M. Thiel W. Angew. Chem., Int. Ed. Engl. 1982, 21: 132

<A NAME="RA41206ST-4D">4d</A> Boche G. Etzrodt H. Marsch M. Thiel W. Angew. Chem., Int. Ed. Engl. 1982, 21: 133

<A NAME="RA41206ST-4E">4e</A> Boche G. Etzrodt H. Tetrahedron Lett. 1983, 24: 5477

<A NAME="RA41206ST-4F">4f</A> Boche G. Etzrodt H. Massa W. Baum G. Angew. Chem., Int. Ed. Engl. 1985, 24: 863

<A NAME="RA41206ST-5A">5a</A> Clark T. Wilhelm D. von Ragué Schleyer P. Tetrahedron Lett. 1982, 23: 3547

<A NAME="RA41206ST-5B">5b</A> Hess BA. Ewig CS. Schaad LJ. J. Org. Chem. 1985, 50: 5869

<A NAME="RA41206ST-5C">5c</A> Skancke A. Nouv. J. Chim. 1985, 9: 577

<A NAME="RA41206ST-6">6</A> van Zandwijk G. Jannsen RAJ. Buck HM. J. Am. Chem. Soc. 1990, 112: 4155

<A NAME="RA41206ST-7A">7a</A> Kos AJ. von Ragué Schleyer P. J. Am. Chem. Soc. 1980, 102: 7928

<A NAME="RA41206ST-7B">7b</A> Sommerfeld T. J. Am. Chem. Soc. 2002, 124: 1119

<A NAME="RA41206ST-7C">7c</A> Jung Y. Heine T. von Ragué Schleyer P. Head-Gordon M. J. Am. Chem. Soc. 2004, 126: 3132

<A NAME="RA41206ST-8A">8a</A> Balci M. McKee ML. von Ragué Schleyer P. J. Phys. Chem. A 2000, 104: 1246

<A NAME="RA41206ST-8B">8b</A> Shainyan BA. Sekiguchi A. THEOCHEM 2005, 728: 1

For ethylene dianion, see:

<A NAME="RA41206ST-9A">9a</A> Sekiguchi A. Nakanishi T. Kabuto C. Sakurai H. J. Am. Chem. Soc. 1989, 111: 3748

<A NAME="RA41206ST-9B">9b</A> Sekiguchi A. Ichinohe M. Nakanishi T. Sakurai H. Chem. Lett. 1993, 267

<A NAME="RA41206ST-9C">9c</A> Sekiguchi A. Ichinohe M. Kabuto C. Sakurai H. Organometallics 1995, 14: 1092

<A NAME="RA41206ST-9D">9d</A> Sekiguchi A. Ichinohe M. Kabuto C. Sakurai H. Bull. Chem. Soc. Jpn. 1995, 68: 2981

<A NAME="RA41206ST-9E">9e</A> Sekiguchi A. Ichinohe M. Kabuto C. Sakurai H. Angew. Chem., Int. Ed. Engl. 1997, 36: 1533

For styrene dianion, see:

<A NAME="RA41206ST-9F">9f</A> Sekiguchi A. Nakanishi T. Kabuto C. Sakurai H. Chem. Lett. 1992, 867

<A NAME="RA41206ST-9G">9g</A> Sekiguchi A. Ichinohe M. Nakanishi T. Kabuto C. Sakurai H. Bull. Chem. Soc. Jpn. 1995, 68: 3215

For benzene dianion, see:

<A NAME="RA41206ST-9H">9h</A> Sekiguchi A. Ebata K. Kabuto C. Sakurai H. J. Am. Chem. Soc. 1991, 113: 1464

<A NAME="RA41206ST-9I">9i</A> Sekiguchi A. Ebata K. Kabuto C. Sakurai H. J. Am. Chem. Soc. 1991, 113: 7081

<A NAME="RA41206ST-9J">9j</A> Ebata K. Setaka W. Inoue T. Kabuto C. Kira M. Sakurai H. J. Am. Chem. Soc. 1998, 120: 1335

<A NAME="RA41206ST-9K">9k</A> Setaka W. Ebata K. Sakurai H. Kira M. J. Am. Chem. Soc. 2000, 122: 7781

For bis(methylene)cyclobutene dianion, see:

<A NAME="RA41206ST-9L">9l</A> Sekiguchi A. Matsuo T. Ebata K. Sakurai H. Chem. Lett. 1996, 1133

For [4]radialene dianion, see:

<A NAME="RA41206ST-9M">9m</A> Sekiguchi A. Matsuo T. Sakurai H. Angew. Chem. Int. Ed. 1998, 37: 1661

<A NAME="RA41206ST-9N">9n</A> Matsuo T. Sekiguchi A. Ichinohe M. Ebata K. Sakurai H. Bull. Chem. Soc. Jpn. 1998, 71: 41

For fulvene dianion, see:

<A NAME="RA41206ST-9O">9o</A> Matsuo T. Sekiguchi A. Ichinohe M. Ebata K. Sakurai H. Organometallics 1998, 17: 3143

<A NAME="RA41206ST-9P">9p</A> Matsuo T. Sekiguchi A. Sakurai H. Bull. Chem. Soc. Jpn. 1999, 72: 1115

For butatriene dianion, see:

<A NAME="RA41206ST-9Q">9q</A> Matsuo T. Tanaka M. Sekiguchi A. Chem. Commun. 2001, 503

<A NAME="RA41206ST-9R">9r</A> Sekiguchi A. Tanaka M. Matsuo T. Silicon Chem. 2004, 1: 345

For tris(methylene)cyclopentene tetraanion, see:

<A NAME="RA41206ST-9S">9s</A> Sekiguchi A. Matsuo T. Kabuto C. Angew. Chem., Int. Ed. Engl. 1997, 36: 2462

<A NAME="RA41206ST-9T">9t</A> Sekiguchi A. Matsuo T. Akaba R. Bull. Chem. Soc. Jpn. 1998, 71: 41

For [5]radialene tetraanion, see:

<A NAME="RA41206ST-9U">9u</A> Matsuo T. Fure H. Sekiguchi A. Chem. Lett. 1998, 1101

<A NAME="RA41206ST-9V">9v</A> Matsuo T. Fure H. Sekiguchi A. Chem. Commun. 1999, 1981

<A NAME="RA41206ST-9W">9w</A> Matsuo T. Fure H. Sekiguchi A. Bull. Chem. Soc. Jpn. 2000, 73: 2129

For bis(ethylene dianion), see:

<A NAME="RA41206ST-9X">9x</A> Matsuo T. Watanabe H. Ichinohe M. Sekiguchi A. Inorg. Chem. Commun. 1999, 2: 510

<A NAME="RA41206ST-9Y">9y</A> Matsuo T. Watanabe H. Sekiguchi A. Bull. Chem. Soc. Jpn. 2000, 73: 1461

For reviews, see:

<A NAME="RA41206ST-10A">10a</A> Sakurai H. Nippon Kagaku Kaishi 1990, 439

<A NAME="RA41206ST-10B">10b</A> Sakurai H. Pure Appl. Chem. 1996, 68: 327

<A NAME="RA41206ST-10C">10c</A> Sekiguchi A. Matsuo T. J. Synth. Org. Chem. Jpn. 1999, 57: 945

<A NAME="RA41206ST-11A">11a</A> Sakurai H. Hayashi J. J. Organomet. Chem. 1974, 70: 85

<A NAME="RA41206ST-11B">11b</A> Fritch JR. Vollhardt KPC. Thompson MR. Day VW. J. Am. Chem. Soc. 1979, 101: 2768

<A NAME="RA41206ST-12A">12a</A> Kaim W. Bock H. J. Organomet. Chem. 1979, 164: 218

<A NAME="RA41206ST-12B">12b</A> Kusumoto T. Hiyama T. Tetrahedron. Lett. 1987, 28: 18074

<A NAME="RA41206ST-12C">12c</A> Sakurai H. Kudo M. Sakamoto K. Nakadaira Y. Kira M. Sekiguchi A. Chem. Lett. 1988, 1441

<A NAME="RA41206ST-13A">13a</A> Sekiguchi A. Tanaka M. Matsuo T. Watanabe H. Angew. Chem. Int. Ed. 2001, 40: 1675

<A NAME="RA41206ST-13B">13b</A> Sekiguchi A. Matsuo T. Tanaka M. Watanabe H. Nakamoto M. Russ. Chem. Bull. Int. Ed. 2004, 53: 1109

<A NAME="RA41206ST-13C">13c</A> Matsuo T. Sekiguchi A. Bull. Chem. Soc. Jpn. 2004, 77: 211

<A NAME="RA41206ST-14">14</A> Kloster-Jensen E. Eliassen GA. Angew. Chem., Int. Ed. Engl. 1985, 24: 565

<A NAME="RA41206ST-15">15</A> Gleiter R. Merger M. Angew. Chem., Int. Ed. Engl. 1997, 36: 2426

<A NAME="RA41206ST-16A">16a</A> Matsuo T. Mizue T. Sekiguchi A. Chem. Lett. 2000, 896

<A NAME="RA41206ST-16B">16b</A> Sekiguchi A. Matsuo T. Watanabe H. Phosphorus, Sulfur Silicon Relat. Elem. 2001, 168-169: 51

<A NAME="RA41206ST-17A">17a</A> Sakurai H. Hayashi J. J. Organomet. Chem. 1972, 39: 365

<A NAME="RA41206ST-17B">17b</A> Kabuto C. Hayashi J. Sakurai H. Kitahara Y. J. Organomet. Chem. 1972, 43: C23

<A NAME="RA41206ST-18">18</A> Sekiguchi A. Matsuo T. Tanaka M. Organometallics 2002, 21: 1072

<A NAME="RA41206ST-19">19</A> Jonas K. Krüger C. Angew. Chem., Int. Ed. Engl. 1980, 19: 520

<A NAME="RA41206ST-20A">20a</A> Elschenbroich C. Salzer A. Organometallics. A Concise Introduction 2nd ed.: VCH; Weinheim: 1992.

<A NAME="RA41206ST-20B">20b</A> Sekiguchi A. Sugai Y. Ebata K. Kabuto C. Sakurai H. J. Am. Chem. Soc. 1993, 115: 1144

<A NAME="RA41206ST-20C">20c</A> Lee VYa. Kato R. Ichinohe M. Sekiguchi A. J. Am. Chem. Soc. 2005, 127: 13142

<A NAME="RA41206ST-21A">21a</A> Paquette LA. Bauer W. Sivik MR. Bühl M. Feigel M. von Ragué Schleyer P. J. Am. Chem. Soc. 1990, 112: 8776

<A NAME="RA41206ST-21B">21b</A> Jiao H. von Ragué Schleyer P. Angew. Chem., Int. Ed. Engl. 1993, 32: 1760

<A NAME="RA41206ST-22">22</A> Ishii K. Kobayashi N. Matsuo T. Tanaka M. Sekiguchi A. J. Am. Chem. Soc. 2001, 123: 5356

<A NAME="RA41206ST-23A">23a</A> Michl J. J. Am. Chem. Soc. 1978, 100: 6801

<A NAME="RA41206ST-23B">23b</A> Michl J. Tetrahedron 1984, 40: 3845

<A NAME="RA41206ST-24A">24a</A> Tajiri A. Hatano M. Bull. Chem. Soc. Jpn. 1972, 45: 962

<A NAME="RA41206ST-24B">24b</A> Allen SD. Mason MG. Schnepp O. Stephens PJ. J. Chem. Phys. Lett. 1975, 30: 140

For reviews, see:

<A NAME="RA41206ST-25A">25a</A> Müllen K. Chem. Rev. 1984, 84: 603

<A NAME="RA41206ST-25B">25b</A> Setzer WN. von Ragué Schleyer P. Adv. Organomet. Chem. 1985, 24: 353

<A NAME="RA41206ST-25C">25c</A> Schade C. von Ragué Schleyer P. Adv. Organomet. Chem. 1987, 27: 169

<A NAME="RA41206ST-25D">25d</A> Rabinovitz M. Top. Curr. Chem. 1988, 14: 99

<A NAME="RA41206ST-25E">25e</A> Maier G. Angew. Chem., Int. Ed. Engl. 1988, 27: 309

<A NAME="RA41206ST-25F">25f</A> Sannigrahi AB. Kar T. Niyogi BG. Hobza P. von Ragué Schleyer P. Chem. Rev. 1990, 90: 1061

<A NAME="RA41206ST-25G">25g</A> Bock H. Ruppert K. Näther C. Havlas Z. Herrmann HF. Arad C. Göbel I. John A. Meuret J. Nick S. Rauschenbach A. Seitz W. Vaupel T. Solouki B. Angew. Chem., Int. Ed. Engl. 1992, 31: 550

<A NAME="RA41206ST-25H">25h</A> Sapse A.-M. von Ragué Schleyer P. Lithium Chemistry: A Theoretical and Experimental Overview Wiley; New York: 1995.

For recent theoretical papers, see:

<A NAME="RA41206ST-26A">26a</A> Balkova A. Bartlett RJ. J. Phys. Chem. 1994, 101: 8972

<A NAME="RA41206ST-26B">26b</A> Glukovtsev MN. Laiter S. Pross A. J. Phys. Chem. 1995, 99: 6828

<A NAME="RA41206ST-26C">26c</A> Gogonea V. von Ragué Schleyer P. Schreiner PR. Angew. Chem. Int. Ed. 1998, 37: 1945

<A NAME="RA41206ST-26D">26d</A> Zilberg S. Haas Y. J. Phys. Chem. A 1998, 102: 10843

<A NAME="RA41206ST-26E">26e</A> Redington R. J. Chem. Phys. 1998, 109: 10781

<A NAME="RA41206ST-26F">26f</A> Wu WSS. Chem. Phys. Lett. 1999, 301: 37

<A NAME="RA41206ST-26G">26g</A> Filatov M. Shaik S. J. Chem. Phys. 1999, 110: 116

<A NAME="RA41206ST-27">27</A> Watts W. Fitzpatrick JD. Pettit R. J. Am. Chem. Soc. 1965, 87: 3253

<A NAME="RA41206ST-28">28</A> Cram DJ. Tanner ME. Thomas R. Angew. Chem., Int. Ed. Engl. 1991, 30: 1024

<A NAME="RA41206ST-29A">29a</A> Kimling H. Krebs A. Angew. Chem., Int. Ed. Engl. 1972, 11: 932

<A NAME="RA41206ST-29B">29b</A> Irngartinger H. Rodewald H. Angew. Chem., Int. Ed. Engl. 1974, 13: 740

<A NAME="RA41206ST-29C">29c</A> Delbaere LTJ. James MNG. Nakamura N. Masamune S. J. Am. Chem. Soc. 1975, 97: 1973

<A NAME="RA41206ST-29D">29d</A> Maier G. Pfriem S. Schäfer U. Matusch R. Angew. Chem., Int. Ed. Engl. 1978, 17: 520

<A NAME="RA41206ST-29E">29e</A> Irngartinger H. Riegler N. Malsch K.-D. Schneider K.-A. Maier G. Angew. Chem., Int. Ed. Engl. 1980, 19: 211

<A NAME="RA41206ST-29F">29f</A> Ermer O. Heilbronner E. Angew. Chem., Int. Ed. Engl. 1983, 22: 402

<A NAME="RA41206ST-29G">29g</A> Irngartinger H. Nixdorf M. Angew. Chem., Int. Ed. Engl. 1983, 22: 403

<A NAME="RA41206ST-29H">29h</A> Maier G. Emrich R. Malsch K.-D. Schneider K.-A. Nixdorf M. Irngartinger H. Chem. Ber. 1985, 118: 2798

<A NAME="RA41206ST-29I">29i</A> Dunitz JD. Krüger C. Irngartinger H. Maverick EF. Wang Y. Nixdorf M. Angew. Chem., Int. Ed. Engl. 1988, 27: 387

<A NAME="RA41206ST-29J">29j</A> Irngartinger H. Nixdorf M. Riegler NH. Krebs A. Kimling H. Pocklington J. Maier G. Malsch K.-D. Schneider K.-A. Chem. Ber. 1988, 121: 673

<A NAME="RA41206ST-29K">29k</A> Irngartinger H. Nixdorf M. Chem. Ber. 1988, 121: 679

<A NAME="RA41206ST-29L">29l</A> Maier G. Born D. Angew. Chem., Int. Ed. Engl. 1989, 28: 1050

<A NAME="RA41206ST-29M">29m</A> Maier G. Fleischer F. Tetrahedron Lett. 1991, 32: 57

<A NAME="RA41206ST-29N">29n</A> Maier G. Born D. Bauer I. Wolf R. Boese R. Cremer D. Chem. Ber. 1994, 127: 173

<A NAME="RA41206ST-29O">29o</A> Maier G. Wolf R. Kalinowski H.-O. Boese R. Chem. Ber. 1994, 127: 191

<A NAME="RA41206ST-29P">29p</A> Maier G. Wolf R. Kalinowski H.-O. Chem. Ber. 1994, 127: 201

<A NAME="RA41206ST-29Q">29q</A> Maier G. Rang H. Emrich R. Liebigs Ann. 1995, 153

<A NAME="RA41206ST-29R">29r</A> Maier G. Rang H. Emrich R. Irngartinger H. Liebigs Ann. 1995, 161

<A NAME="RA41206ST-29S">29s</A> Maier G. Fleischer F. Liebigs Ann. 1995, 169

<A NAME="RA41206ST-29T">29t</A> Maier G. Rang H. Fleischer F. Kalinowski H.-O. Liebigs Ann. 1995, 173

<A NAME="RA41206ST-30">30</A> Maier G. Lage HW. Reisenauer HP. Angew. Chem., Int. Ed. Engl. 1981, 20: 976

<A NAME="RA41206ST-31">31</A> Maier G. Neudert J. Wolf O. Angew. Chem. Int. Ed. 2001, 40: 1674

<A NAME="RA41206ST-32">32</A> O’Brien DH. Russell CR. Hart AJ. J. Am. Chem. Soc. 1976, 98: 7427

<A NAME="RA41206ST-33A">33a</A> Peterson RF. Baker RTK. Wolfgang RL. Tetrahedron Lett. 1969, 54: 4749

<A NAME="RA41206ST-33B">33b</A> Shevlin PB. Wolf AP. J. Am. Chem. Soc. 1970, 92: 406

<A NAME="RA41206ST-33C">33c</A> Rodewald LB. Lee H. J. Am. Chem. Soc. 1973, 95: 623

<A NAME="RA41206ST-33D">33d</A> Maier G. Hoppe M. Lanz K. Reisenauer HP. Tetrahedron Lett. 1984, 25: 5645

<A NAME="RA41206ST-34">34</A> Maier G. Pfriem S. Schäfer U. Malsch KD. Matusch R. Chem. Ber. 1981, 114: 3965

<A NAME="RA41206ST-35">35</A> Maier G. Neudert J. Wolf O. Pappusch D. Sekiguchi A. Tanaka M. Matsuo T. J. Am. Chem. Soc. 2002, 124: 13819

Tanaka, M.; Sekiguchi, A. unpublished results.

<A NAME="RA41206ST-37">37</A> Loerzer T. Malinek R. Lüttke W. Franz LH. Malsch K.-D. Maier G. Angew. Chem., Int. Ed. Engl. 1983, 22: 878

<A NAME="RA41206ST-38A">38a</A> Irngartinger H. Goldmann A. Jahn R. Nixdorf M. Rodewald H. Maier G. Malsch K.-D. Emrich R. Angew. Chem., Int. Ed. Engl. 1984, 23: 993

<A NAME="RA41206ST-38B">38b</A> Irngartinger H. Jahn R. Maier G. Emrich R. Angew. Chem., Int. Ed. Engl. 1987, 26: 356

<A NAME="RA41206ST-39">39</A> Kaftory M. Kapon M. Botoshansky M. The Chemistry of Organic Silicon Compounds Vol. 2: Rappoport Z. Apeloig Y. Wiley; Chichester: Part 1, Chap. 5. 1998.

<A NAME="RA41206ST-40">40</A> Cremer D. Kraka E. J. Am. Chem. Soc. 1985, 107: 3800

<A NAME="RA41206ST-41A">41a</A> Dill JD. Greenberg A. Liebman JF. J. Am. Chem. Soc. 1979, 101: 6814

<A NAME="RA41206ST-41B">41b</A> Clark T. Spitznagel GW. Klose R. von Ragué Schleyer P. J. Am. Chem. Soc. 1984, 106: 4412

<A NAME="RA41206ST-42">42</A> Sekiguchi A. Tanaka M. J. Am. Chem. Soc. 2003, 125: 12684

<A NAME="RA41206ST-43">43</A> Maciel GE. Mclver JW. Ostlund NS. Pople JA. J. Am. Chem. Soc. 1970, 92: 1

<A NAME="RA41206ST-44">44</A> Newton ND. Schulman JM. Manus MM. J. Am. Chem. Soc. 1974, 96: 17

<A NAME="RA41206ST-45">45</A> Osawa S. Sakai M. Osawa E. J. Phys. Chem. A 1997, 101: 1378

<A NAME="RA41206ST-46A">46a</A> Eaton PE. Maggini M. J. Am. Chem. Soc. 1988, 110: 7230

<A NAME="RA41206ST-46B">46b</A> Gilardi R. Maggini M. Eaton PE. J. Am. Chem. Soc. 1988, 110: 7232

<A NAME="RA41206ST-47">47</A> Ermer O. Bell P. Schäfer J. Szeimies G. Angew. Chem., Int. Ed. Engl. 1989, 28: 473

<A NAME="RA41206ST-48A">48a</A> Xie Y. Schaefer HF. Chem. Phys. Lett. 1989, 161: 516

<A NAME="RA41206ST-48B">48b</A> Xie Y. Schaefer HF. Chem. Phys. Lett. 1990, 168: 249

<A NAME="RA41206ST-49">49</A> Tanaka M. Sekiguchi A. Angew. Chem. Int. Ed. 2005, 44: 5821

<A NAME="RA41206ST-50">50</A> Lee VYa. Takanashi K. Matsuno T. Ichinohe M. Sekiguchi A. J. Am. Chem. Soc. 2004, 126: 4758

<A NAME="RA41206ST-51">51</A> Lee VYa. Takanashi K. Ichinohe M. Sekiguchi A. J. Am. Chem. Soc. 2003, 125: 6012

<A NAME="RA41206ST-52">52</A> Jenkins DM. Teng W. Englich U. Stone D. Ruhlandt-Senge K. Organometallics 2001, 20: 4600

<A NAME="RA41206ST-53">53</A> von Ragué Schleyer P. Maerker G. Dransfeld A. Jiao H. von Eikema Hommes NJR. J. Am. Chem. Soc. 1996, 118: 6317

<A NAME="RA41206ST-54">54</A> Lee VYa. Takanashi K. Ichinohe M. Sekiguchi A. Angew. Chem. Int. Ed. 2004, 43: 6703

<A NAME="RA41206ST-55A">55a</A> Dawd P. Irngartinger H. Chem. Rev. 1989, 89: 985

<A NAME="RA41206ST-55B">55b</A> Levin MD. Kaszynski P. Chem. Rev. 2000, 100: 169

<A NAME="RA41206ST-56">56</A> Lee VYa. Ichinohe M. Sekiguchi A. J. Am. Chem. Soc. 2002, 124: 9962

<A NAME="RA41206ST-57A">57a</A> Lee VYa. Ichinohe M. Sekiguchi A. J. Am. Chem. Soc. 2000, 122: 12604

<A NAME="RA41206ST-57B">57b</A> Özkan I. Kinal A. Balci M. J. Phys. Chem. A 2004, 108: 507

<A NAME="RA41206ST-58">58</A> Takanashi K. Lee VYa. Matsuno T. Ichinohe M. Sekiguchi A. J. Am. Chem. Soc. 2005, 127: 5768