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Yttrium Complexes of the Chelating, C2-Symmetric, Bis(silylamido)biphenyl Ligand [DADMB]2- (={[6,6‘-Me2-(C6H3)2](2,2‘-NSiMe2tBu)2}2-)

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journal contribution
posted on 01.07.1999 by Tomislav I. Gountchev, T. Don Tilley
The yttrium bis(silylamido)biphenyl complex [DADMB]YCl(THF)2 (2; DADMB = 2,2‘-bis((tert-butyldimethylsilyl)amido)-6,6‘-dimethylbiphenyl) was prepared from Li2[DADMB]·2THF and YCl3(THF)3, and its structure was determined by X-ray crystallography. Compound 2 reacts with MeLi and (Me3Si)2CHLi to give the corresponding alkyl derivatives [DADMB]YMe(THF)2 (3) and [DADMB]Y[CH(SiMe3)2](THF)(OEt2) (5), respectively. In the presence of silicone grease, the reaction of 2 with MeLi produces the yttrium trimethylsiloxide complex [DADMB]Y(OSiMe3)(THF)2 (4), which was also crystallographically characterized. Both 3 and 5 react with phenylsilane or H2 to give the insoluble, dimeric yttrium hydride {[DADMB]Y(μ-H)(THF)}2·C6H6 (6). The alkyl derivatives 3 and 5 exhibit only limited olefin polymerization activity; however, the hydride 6 reacts rapidly with ethylene or 1-hexene to give a single insertion product. The resulting yttrium ethyl complex 7 was structurally characterized. Compound 6 reacts with pyridine to produce a mixture of the isomeric 1,2- and 1,4-insertion products 9 and 10, [DADMB]Y(NC5H6)(pyr)2. Compound 9 converts quantitatively to 10 upon heating.