The amine elimination reaction of Me 2 Si(1-indenyl) 2 ( 1, (SBI)H 2 ) and Hf(NMe 2 ) 4 ( 2 ) affords rac -Me 2 Si(η 5 -1-indenyl) 2 Hf(NMe 2 ) 2 ( rac - 3, rac -(SBI)Hf(NMe 2 ) 2 ) in 20% isolated yield. This reaction proceeds by initial formation of a mono(indenyl) intermediate, (η 5 -C 9 H 6 SiMe 2 C 9 H 7 )Hf(NMe 2 ) 3 ( 4 ), which reacts reversibly with a second equivalent of 2 to form a binuclear complex, {μ-η 5:η 5 -Me 2 Si(1-indenyl) 2 }{Hf(NMe 2 ) 3 } 2 ( 5 ), and undergoes reversible intramolecular amine elimination to form rac - 3 and meso - 3 . The novel C 1 -symmetric ansa -metallocene {Me 2 Si(η 5 -1-indenyl)(η 3 -2-indenyl)}Hf(NMe 2 ) 2 ( 6 ), in which one of the indenyl groups is bridged through the 2-position, is observed as a side product in the synthesis of 3 . Complex 6 has been prepared in 21% isolated yield by thermolysis of 4 (or mixtures of 1 and 2 ) at 160 °C and can be converted to {Me 2 Si(η 5 -1-indenyl)(η 3 -2-indenyl)}HfMe 2 ( 7, 100% NMR) by reaction with AlMe 3 . The molecular structures of rac - 3 and 6 have been determined by X-ray crystallography.
No takes yet. Share an insight, caveat, or question.
Christopher et al. (1997) studied this question.