Yttrium complexes of the chelating, C-2-symmetric, bis(silylamido)biphenylligand [DADMB](2-)(={[6,6 '-Me-2- (C6H3)(2)] (2,2 '-NSiMe2(t)Bu)2}(2-))

The yttrium bis(silylamido)biphenyl complex [DADMB]YCl(THF)(2) (2; DADMB = 2,2'-bis((tert-butyldimethylsilyl)amido)-6,6'-dimethylbiphenyl) was prepare d from Li-2[DADMB].2THF and YCl3(THF)(3), and its structure was determined by X-ray crystallography. Compound 2 reacts with MeLi and (Me3Si)(2)CHLi 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 c haracterized. Both 3 and 5 react with phenylsilane or H-2 to give the insol uble, dimeric yttrium hydride {[DADMB]Y(mu-H)(THF)}(2). C6H6 (6) The alkyl derivatives 3 and 5 exhibit only limited olefin polymerization activity; ho wever, the hydride 6 reacts rapidly with ethylene or 1-hexene to give a sin gle insertion product. The resulting yttrium ethyl complex 7 was structural ly characterized. Compound 6 reacts with pyridine to produce a mixture of t he isomeric 1,2- and 1,4-insertion products 9 and 10, [DADMB]Y(NC5H6)(pyr)( 2). Compound 9 converts quantitatively to 10 upon heating.