pubs.acs.org/Organometallics Published on Web 02/08/2011 r 2011 American Chemical Society Organometallics 2011, 30, 1157–1161 1157 DOI: 10.1021/om1011374 Reactions of Five-Membered Metallacyclocumulenes Cp 2 M(η 4 - t -Bu-C 4 - t- Bu ) (M = Ti, Zr ) with Diisobutylaluminum Hydride Vladimir V. Burlakov, † Katharina Kaleta, ‡ Torsten Beweries, ‡ Perdita Arndt, ‡ Wolfgang Baumann, ‡ Anke Spannenberg, ‡ Vladimir B. Shur, † and Uwe Rosenthal* ,‡ † A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov St. 28, 119991, Moscow, Russia, and ‡ Leibniz-Institut f € ur Katalyse e. V. an der Universit € at Rostock, Albert-Einstein-Str. 29a, D-18059 Rostock, Germany Received December 3, 2010 Reactions of the five-membered metallacyclocumulenes Cp 2 M(η 4 -t-Bu-C 4 -t-Bu) (M = Ti, Zr) with the Lewis Acid i-Bu 2 AlH were studied. Cp 2 Ti(η 4 -t-Bu-C 4 -t-Bu) (1) reacts with i-Bu 2 AlH to give a heterobimetallic complex which was isolated as the THF adduct Cp 2 Ti[μ-η 1 :η 2 -t-BuCC- CHC-t-Bu)(μ-H)(i-BuAl)(THF)] (4). The reaction of the corresponding zirconocene compound Cp 2 Zr(η 4 -t-Bu-C 4 -t-Bu) (2) with i-Bu 2 AlH results in a cleavage of the central CdC bond of the metallacyclocumulene C 4 chain and formation of the dinuclear complex 6 and the dinuclear acetylide [(Cp 2 Zr) 2 (μ-CtC-t-Bu) 2 ]. In addition to the formation of 6 and the acetylide species an elimination of the butadiyne takes place, which gives in the subsequent interaction with i-Bu 2 AlH the zwitterionic aluminum cluster 7. Alternatively, complex 7 is also formed in the direct reaction of the butadiyne with a 3-fold excess of i-Bu 2 AlH. The molecular structures of 4 and 7 were confirmed by X-ray analysis. Metallacycles of transition metals are of great interest in many catalytic processes, and recent studies are dealing with their role in polymerization as well as oligomerization reac- tions. Thus, the investigation of structural properties and reactivity of such metallacyclic complexes is a topic of current interest in group 4 organometallic chemistry. 1 Tita- nium and zirconium complexes of the type Cp 2 M(η 4 -t-Bu- C 4 -t-Bu) were the first examples for the rather unusual structural motif of five-membered metallacyclocumulenes (i.e., 1-metallacyclopenta-2,3,4-trienes). 2-4 Recently we de- scribed the reaction of di-n-butylhafnocene with di-tert- butylbutadiyne, which gives the first structurally character- ized hafnacyclocumulene, Cp 2 Hf(η 4 -t-Bu-C 4 -t-Bu), 5 now enabling us to perform comparative studies on a series of Cp-substituted complexes of the type Cp 2 M(η 4 -t-Bu-C 4 -t- Bu) (M = Ti, Zr, Hf) (e.g. investigation of the influence of the different metals on the products of the reactions with Lewis acids). For the corresponding complexes with penta- methylcyclopentadienyl ligands and different substituents at the C 4 chain Cp* 2 Zr(η 4 -R-C 4 -R) (R = Me 3 Si, Me, Ph) the reactivity toward the Lewis acids B(C 6 F 5 ) 3 6 and i-Bu 2 AlH 7 and the catalytic activity in the polymerization of ethylene and ε-caprolactone was investigated in detail. 8 In this case a very strong influence of the substituents at the metallacyclic system on the nature of the reaction products was found. Very recently we described reactions of Cp 2 M(η 4 -t-Bu-C 4 -t- Bu) (M = Ti, Hf) with B(C 6 F 5 ) 3 or i-Bu 2 AlH 9 (Scheme 1). Reaction of the titanacyclocumulene 1 with catalytic amounts of B(C 6 F 5 ) 3 9 results in the formation of the previously described dinuclear complex A, which then undergoes further reaction with B(C 6 F 5 ) 3 to give the known zwitterionic Ti(III) species 10 and the ene-yne t-BuCHdCH-CtC-t-Bu. The hafnacyclocu- mulene Cp 2 Hf(η 4 -t-Bu-C 4 -t-Bu) reacts with B(C 6 F 5 ) 3 to give the dinuclear complex B, which consists of a cationic part with two hafnocene centers bridged unsymmetrically by butadiyne and acetylide moieties and an alkynyl boranate representing the anionic part. In the reaction with the Lewis acid i-Bu 2 AlH the complex Cp 2 Hf(CtC-t-Bu)[C(Al-i-Bu 2 )dCH(t-Bu)] (C) is formed 9 (Scheme 1). *To whom correspondence should be addressed. Tel: þþ49-381-1281- 176. Fax: þþ49-381-1281-51176. E-mail: uwe.rosenthal@catalysis.de. (1) Rosenthal, U.; Burlakov, V. V.; Bach, M. A.; Beweries, T. Chem. Soc. Rev. 2007, 36, 689. (2) Burlakov, V. V.; Ohff, A.; Lefeber, C.; Tillack, A.; Baumann, W.; Kempe, R.; Rosenthal, U. Chem. Ber. 1995, 128, 967. (3) Rosenthal, U.; Ohff, A.; Baumann, W.; Kempe, R.; Tillack, A.; Burlakov, V. V. Angew. Chem., Int. Ed. Engl. 1994, 33, 1605. (4) For a review see: Rosenthal, U.; Burlakov, V. V.; Arndt, P.; Baumann, W.; Spannenberg, A. Organometallics 2005, 24, 456. (5) (a) Burlakov, V. V.; Bogdanov, V. S.; Lyssenko, K. A.; Petrovskii, P. V.; Beweries, T.; Arndt, P.; Rosenthal, U.; Shur, V. B. Russ. Chem. Bull. Int. Ed. 2008, 57, 1319. (b) Burlakov, V. V.; Beweries, T.; Bogdanov, V. S.; Arndt, P.; Baumann, W.; Spannenberg, A.; Lyssenko, K. A.; Shur, V. B.; Rosenthal, U. Organometallics 2009, 28, 2864. (6) Burlakov, V. V.; Arndt, P.; Baumann, W.; Spannenberg, A.; Rosenthal, U. Organometallics 2004, 23, 5188. (7) Burlakov, V. V.; Arndt, P.; Baumann, W.; Spannenberg, A.; Rosenthal, U. Organometallics 2004, 23, 4160. (8) Burlakov, V. V.; Bach, M. A.; Klahn, M.; Arndt, P.; Baumann, W.; Spannenberg, A.; Rosenthal, U. Macromol. Symp. 2006, 236, 48. (9) Burlakov, V. V.; Beweries, T.; Kaleta, K.; Bogdanov, V. S.; Arndt, P.; Baumann, W.; Spannenberg, A.; Shur, V. B.; Rosenthal, U. Orga- nometallics 2010, 29, 2367. In this paper, the chemical shifts for the Hf-Ct and Hf-Cd atoms have been interchanged inadvertently. The assignment now given is the correct one. (10) (a) Burlakov, V. V.; Troyanov, S. I.; Letov, A. V.; Mysov, E. I.; Furin, G. G.; Shur, V. B. Izv. Akad. Nauk, Ser. Khim. 1999, 1022; Russ. Chem. Bull. 1999, 1012. (b) Burlakov, V. V.; Troyanov, S. I.; Letov, A. V.; Strunkina, L. I.; Minacheva, M. Kh.; Furin, G. G.; Rosenthal, U.; Shur, V. B. J. Organomet. Chem. 2000, 598, 243.