DOI: 10.1002/asia.201000598 Olefin Hydrosilylation Catalysts Based on Allyl Bis(phenolato) Complexes of the Early Lanthanides Elise Abinet, Thomas P. Spaniol, and Jun Okuda* [a] Dedicated to Professor Eiichi Nakamura on the occasion of his 60th birthday Olefin hydrosilylation is commonly catalyzed by platinum compounds, such as the Speier [1a] or Karsted catalysts. [1b] Ho- mogeneous late-transition-metal (Co, Rh, Pd, Pt) catalysts have been extensively optimized with respect to activity, re- gioselectivity, and stereoselectivity. [1c] Lanthanide complexes are also known to efficiently catalyze the hydrosilylation of olefins. [2] Their catalytic activity increases with the size of the central metal, as the crucial steps involve s-bond meta- thesis. Therefore, inert ancillary ligands other than the ubiq- uitous metallocene frameworks are not numerous in the lit- erature. [2, 3] Some time ago, sulfur-linked bis(phenolato) ligand scaf- folds that contain two hard anionic oxygen donors along with a soft thioether moiety were introduced, and these scaf- folds can be broadly modified in terms of their steric bulk. [4a–c] These scaffolds have allowed the development of efficient Group 4 metal catalysts for the stereoselective polymerization of styrene, [4d–f] and are also effective for sup- porting larger lanthanide central atoms, such as monomeric [SmACHTUNGTRENNUNG(tbmp)ACHTUNGTRENNUNG(OAr)ACHTUNGTRENNUNG(thf)] [5] (tbmp = 6,6’-thiobis(2-tert-butyl-4- methylphenolate)) and silylamido complexes of scandium, yttrium, and lutetium [Ln(L){NACHTUNGTRENNUNG(SiMe 3 ) 2 }] (L = (OSSO)-type 1,w-dithiaalkenediyl-bridged bis(phenolate) ligand). [6] The alkyl complexes of lutetium [Lu(L)ACHTUNGTRENNUNG(CH 2 SiMe 3 )ACHTUNGTRENNUNG(thf) n ] (L = tbmp, mtbmp: 6,6’-methylenebis(sulfanediyl)bis(2-tert-butyl- 4-methylphenolate), etbmp (6,6’-ethane-1,2-diylbis(sulfane- diyl)bis(2,4-di-tert-butylphenolate)), n = 1–2) and the corre- sponding hydride complexes showed high activity and regio- selectivity in the hydrosilylation of 1-hexene. [7] As non-met- allocene hydride complexes of the lanthanides are extremely unstable and difficult to manipulate, [7c] we took advantage of the thermal stability of the trisACHTUNGTRENNUNG(allyl) [LnACHTUNGTRENNUNG(h 3 -C 3 H 5 ) 3 ACHTUNGTRENNUNG(diox)] (Ln = Y, La, Ce, Pr, Nd, Sm; diox = 1,4-dioxane) [8–10] com- plexes for the synthesis of precatalysts. Herein, we report that non-metallocene allyl complexes of early rare-earth metals containing a 1,w-dithiaalkenediyl-bridged bis(pheno- late) ligand show high activity and regioselectivity as preca- talysts for the hydrosilylation of styrene. A series of allyl bis(phenolato) complexes [Ln(L)ACHTUNGTRENNUNG(h 3 - C 3 H 5 )ACHTUNGTRENNUNG(thf) 1À2 ] (L = tbbp, Y 1, La 2 ;L = etbbp, La 3, Ce 4, Nd 5, Sm 6) were synthesized in tetrahydrofuran by reacting the trisACHTUNGTRENNUNG(allyl) complex [LnACHTUNGTRENNUNG(h 3 -C 3 H 5 ) 3 ACHTUNGTRENNUNG(diox)] [10] with the bis- ACHTUNGTRENNUNG(phenol) through propene elimination (Scheme 1). The li- gands containing both one and two sulfur donor atoms in the backbone were found to be suitable as supporting li- gands for the monoACHTUNGTRENNUNG(allyl)-lanthanide fragment. The medium-sized yttrium as well as the largest lantha- nide, lanthanum, were straightforwardly coordinated with the (OSO)-type bisACHTUNGTRENNUNG(phenol) tbbp ligand. Recrystallization of yttrium complex 1 from a tetrahydrofuran/n-pentane mix- ture gave crystals suitable for X-Ray diffraction, which re- vealed that the geometry around the yttrium center could be best described as pentagonal bipyramidal with three tet- rahydrofuran molecules in the plane (Figure 1). [a] Dipl.-Chem. E. Abinet, Dr. T. P. Spaniol, Prof. Dr. J. Okuda Institut für Anorganische Chemie RWTH Aachen University Landoltweg 1, 52074 Aachen (Germany) Fax: (+ 49) 241-80-92644 E-mail : jun.okuda@ac.rwth-aachen.de Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/asia.201000598. Scheme 1. [LnACHTUNGTRENNUNG(tbbp)ACHTUNGTRENNUNG(h 3 -C 3 H 5 )ACHTUNGTRENNUNG(thf) 3À4 ] (Ln = Y 1, La 2) and [LnACHTUNGTRENNUNG(etbbp)- ACHTUNGTRENNUNG(h 3 -C 3 H 5 )ACHTUNGTRENNUNG(thf) 1À2 ] (Ln = La 3, Ce 4, Nd 5, Sm 6). Chem. Asian J. 2011, 6, 389 – 391  2011 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim 389