A Reactivity Change of a Strontium Monohydroxide by Umpolung to an Acid Sankaranarayanapillai Sarish, Sharanappa Nembenna, Selvarajan Nagendran, Herbert W. Roesky,* Aritra Pal, Regine Herbst-Irmer, Arne Ringe, and Jörg Magull Institut für Anorganische Chemie, UniVersität Göttingen, Tammannstrasse 4, 37077 Göttingen, Germany Received February 15, 2008 Controlled hydrolysis of strontium amide LSrN(SiMe 3 ) 2 (thf) (L ) CH(CMe2,6-i-Pr 2 C 6 H 3 N) 2 )(1) gave an unprecedented example of a hydrocarbon-soluble strontium hydroxide, [LSr(thf)(µ-OH) 2 Sr(thf) 2 L] (2). In compound 2, the tetrahydrofuran (THF) molecules can easily replaced by benzophenone and triphenylphosphine oxide to yield [LSr(µ- OH)(OCPh 2 )] 2 (3) and [LSr(µ-OH)(OPPh 3 )] 2 (4) compounds. Among the two strontium atoms of 2, one is coordinated to a single THF molecule, while the other is coordinated to two THF molecules. Interestingly, strontium hydroxide complex 2 behaves as an acid in its reaction with Zr(NMe 2 ) 4 and results in a heterobimetallic oxide, [LSr(µ- O)Zr(NMe 2 ) 3 ] 2 (5). Compound 5 is dimeric in the solid state and contains a Sr 2 Zr 2 O 2 core. Introduction The so-called water effect in organometallic compounds has resulted in the formation of various interesting hydroxide complexes. 1 The reaction of these hydroxides with suitable metal precursors generally leads to the formation of poly- metallic oxides 2 that are emerging as an important class of compounds due to their potential application in catalysis. 3 Therefore, we have prepared various p-block hydroxides and have been successful in assembling novel heterobi- and heteropolymetallic oxides by utilizing the acidic character of these hydroxide complexes. 4 For example, the heterodi- metallic compound LAl(Me)(µ-O)Zr(Me)Cp 2 (L ) CH(C- Me2,6-i-Pr 2 C 6 H 3 N) 2 ) has been obtained by the reaction of LAl(Me)OH with Cp 2 ZrMe 2 , and we have demonstrated that it is a versatile catalyst in ethylene polymerization. 5 Also, the cubic silicon-titanium µ-oxo complex obtained by the reaction of an aminosilanetriol with Ti(OEt) 4 showed excel- lent catalytic activity in the epoxidation of cyclohexene and cyclooctene by t-butyl hydroperoxide. 6 In view of this importance, one may think of a possible extension of these principles to group 2 elements. Nevertheless, two major issues that need to be addressed are the synthesis of stable and soluble group 2 hydroxides and the basicity of these hydroxides. The preparation of group 2 hydroxides, mainly those with heavier metals, is difficult (due to the large atomic radii and high ionic character of these elements), 7 and * To whom correspondence should be addressed. Email: hroesky@ gwdg.de. (1) (a) Roesky, H. W.; Walawalkar, M. G.; Murugavel, R. Acc. Chem. Res. 2001, 34, 201–211. (b) Roesky, H. W.; Singh, S.; Jancik, V.; Chandrasekhar, V. Acc. Chem. Res. 2004, 37, 969–981. (2) (a) See, for examples of mixed metal oxides containing alkaline earth metals: Kennedy, A. R.; Mulvey, R. E.; Rowlings, R. B. J. Am. Chem. Soc. 1998, 120, 7816–7824. (b) Kennedy, A. R.; Mulvey, R. E.; Rowlings, R. B. Angew. Chem., Int. Ed. 1998, 37, 3180–3183. (3) (a) Singh, S.; Roesky, H. W. Dalton Trans. 2007, 1360–1370. (b) Gurubasavaraj, P. M.; Mandal, S. K.; Roesky, H. W.; Oswald, R. B.; Pal, A.; Noltemeyer, M. Inorg. Chem. 2007, 46, 1056–1061. (4) (a) Mandal, S. K.; Gurubasavaraj, P. M.; Roesky, H. W.; Schwab, G.; Stalke, D.; Oswald, R. B.; Dolle, V. Inorg. Chem. 2007, 46, 10158– 10167. (b) Mandal, S. K.; Gurubasavaraj, P. M.; Roesky, H. W.; Oswald, R. B.; Magull, J.; Ringe, A. Inorg. Chem. 2007, 46, 7594– 7600. (c) Gurubasavaraj, P. M.; Roesky, H. W.; Sharma, P. M. V.; Oswald, R. B.; Dolle, V.; Pal, A. Organometallics 2007, 26, 3346– 3351. (d) Nembenna, S.; Roesky, H. W.; Mandal, S. K.; Oswald, R. B.; Pal, A.; Herbst-Irmer, R.; Noltemeyer, M.; Schmidt, H.-G. J. Am. Chem. Soc. 2006, 128, 13056–13057. (e) Chai, J.; Jancik, V.; Singh, S.; Zhu, H.; He, C.; Roesky, H. W.; Schmidt, H.-G.; Noltemeyer, M.; Hosmane, N. S. J. Am. Chem. Soc. 2005, 127, 7521–7528. (f) Winkhofer, N.; Voigt, A.; Dorn, H.; Roesky, H. W.; Steiner, A.; Stalke, D.; Reller, A. Angew. Chem., Int. Ed. Engl. 1994, 33, 1352–1354. (5) (a) Bai, G.; Singh, S.; Roesky, H. W.; Noltemeyer, M.; Schmidt, H.- G. J. Am. Chem. Soc. 2005, 127, 3449–3455. (b) Roesky, H. W.; Bai, G.; Jancik, V.; Singh, S. European Patent, PCT/EP, 2005/002741, 2005; Int. Pat. Classification C07F17/00. (6) Fujiwara, M.; Wessel, H.; Hyung-Suh, P.; Roesky, H. W. Tetrahedron 2002, 58, 239–243. (7) (a) Hanusa, T. P. Polyhedron 1990, 9, 1345–1362. (b) Hanusa, T. P. Coord. Chem. ReV. 2000, 210, 329–367. (c) Westerhausen, M. Angew. Chem. 2001, 113, 3063–3065. (d) Westerhausen, M. Angew. Chem., Int. Ed. 2001, 40, 2975–2977. (e) Alexander, J. S.; Ruhlandt-Senge, K. Eur. J. Inorg. Chem. 2002, 2761–2774. (f) There are some O-centered cage compounds in the literature. See, for example: Maudez, W.; Meuwly, M.; Fromm, K. M. Chem.sEur. J. 2007, 13, 8302–8316. Inorg. Chem. 2008, 47, 5971-5977 10.1021/ic800284u CCC: $40.75  2008 American Chemical Society Inorganic Chemistry, Vol. 47, No. 13, 2008 5971 Published on Web 05/23/2008