High temperature synthesis of some strontium and barium 2,6-dibenzylphenolates Marcus L. Cole a,b , Glen B. Deacon a , Craig M. Forsyth a , Peter C. Junk a,c, * , Kathryn M. Proctor c , Janet L. Scott c , Christopher R. Strauss c a School of Chemistry, Monash University, Clayton, Vic. 3800, Australia b School of Chemistry and Physics, University of Adelaide, Adelaide, SA 5005, Australia c Special Research Centre for Green Chemistry, Monash University, Vic. 3800, Australia Received 27 March 2006; accepted 8 May 2006 Available online 16 May 2006 Abstract Direct treatment of HOdbp (= 2,6-dibenzylphenol) with strontium or barium metal in the absence of solvent at high temperature pro- vides the corresponding phenolates Sr(Odbp) 2 and Ba(Odbp) 2 . Recrystallisation of Ba(Odbp) 2 from THF gave a good yield of the crys- talline dimer [Ba(Odbp) 2 (THF)] 2 Æ 2THF. Attempted recrystallisation of Sr(Odbp) 2 from THF mostly yielded microcrystalline material characterized as [Sr(Odbp) 2 ] n but on one occasion gave a small crop of crystalline [Sr 9 (Odbp) 8 (O 2 SiMe 2 ) 4 (OH) 2 (THF) 6 (OH 2 ) 2 ] Æ 6THF derived from the adventitious reaction of Sr(Odbp) 2 with dimethylsilicone grease ({OSiMe 2 } 1 ). In the solid-state [Ba(Odbp) 2 (THF)] 2 Æ 2THF displays significant intramolecular Bap-arene interactions with the pendant benzyl substituents. [Sr 9 (Odbp) 8 (O 2 SiMe 2 ) 4 - (OH) 2 (THF) 6 (OH 2 ) 2 ] Æ 6THF features a square prismatic [Sr(O 2 SiMe 2 ) 4 ] 6 core capped by two inverse crown-like square [Sr 4 (Odbp) 4 - (OH)(L) 4 ] 3+ units, where L = OH 2 or THF, that are staggered with respect to the cuboidal core. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Strontium; Barium; Phenolates; X-ray crystal structures 1. Introduction There has been significant recent interest in alkaline earth phenolate chemistry, focussing particularly on stron- tium and barium, due to their potential use as precursors to form binary and ternary oxides via sol–gel or MOCVD processes [1]. By a judicious choice of ligands, complexes may be isolated that have significant but weak Mp-arene interactions. These interactions can have implications for reactivity due to their potential displacement by stronger binding, small molecules. Phenolate ligands with aryl groups in the 2,6-positions have the inherent functionality to induce such interactions and this has been the subject of many of our previous investigations. Primarily we have been concerned with the 2,6-diphenylphenolate (Odpp) ligand and have uncovered some interesting interactions in the solid state with both rare earth [2,3] and alkaline earth metals [4]. The phenolate chemistry of strontium and barium is dominated by the formation of aggregates or insoluble polymeric material, particularly when relatively non-bulky phenolate ligands are used. In most cases, isolable material is only obtained when polar donor solvents such as THF [5], HMPA (= hexamethylphosphoramide) [6,7] or TMEDA (=N,N 0 -tetramethylethylenediamine) [7] are used to de-aggregate the clustered compounds. When bulkier phenols such as 2,6-di-tert-butyl-4-X-phenol (X = methyl, tert-butyl) are used, monomeric and dimeric complexes can be isolated, but again, solvated species dominate [8]. We have recently shown that homoleptic calcium, stron- tium and barium 2,6-diphenylphenolate (Odpp) complexes can be synthesised by the high temperature, solvent-free 0277-5387/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2006.05.003 * Corresponding author. Tel.: +61 3 9905 4570; fax: +61 3 9905 4597. E-mail address: peter.junk@sci.monash.edu.au (P.C. Junk). www.elsevier.com/locate/poly Polyhedron 26 (2007) 244–249