Selective Synthesis, Structure, and Catalytic Behavior of meso-Divalent 1,1‘-(3-Oxapentamethylene)-Bridged Bis(indenyl)lanthanidocenes

Mesomeric divalent 1,1‘-(3-oxapentamethylene)-bridged bis(indenyl)lanthanidocenes, meso-[O(CH<INF>2</INF>CH<INF>2</INF>C<INF>9</INF>H<INF>6</INF>)<INF>2</INF>]Ln·(DME) (Ln = Sm (<BO>2</BO>),Yb (<BO>3</BO>)), have been synthesized by reduction of a mixture of rac/meso-[O(CH<INF>2</INF>CH<INF>2</INF>C<INF>9</INF>H<INF>6</INF>)<INF>2</INF>]LnCl·THF (Ln = Sm, Yb) with Na or reaction of LnI<INF>2</INF> (Ln = Sm, Yb) with [O(CH<INF>2</INF>CH<INF>2</INF>C<INF>9</INF>H<INF>6</INF>K)<INF>2</INF>] in THF followed by recrystallization in DME. The structures of these meso, ansa-lanthanidocenes were determined by X-ray diffraction analysis. The factors that dictated the rac/meso selectivity are discussed. Nonbridged divalent lanthanide complexes (CH<INF>3</INF>OCH<INF>2</INF>CH<INF>2</INF>C<INF>9</INF>H<INF>6</INF>)<INF>2</INF>Ln^II (Ln = Sm (<BO>4</BO>), Yb (<BO>5</BO>)) were also synthesized for comparison by the reaction of LnI<INF>2</INF> (Ln = Sm, Yb) with (CH<INF>3</INF>OCH<INF>2</INF>CH<INF>2</INF>C<INF>9</INF>H<INF>6</INF>)<INF>2</INF>K in THF. Stereoselective polymerization of methyl methacrylate with these divalent lanthanide complexes as single-component catalysts was preliminarily investigated.