Patent ID: 7442407

Claim:
A compound of the formula (I) wherein M stands for Ta or Nb, R 1 and R 2 mutually independently denote optionally substituted C 1 to C 12 alkyl, C 5 to C 12 cycloalkyl or C 6 to C 10 aryl radicals, 1-alkenyl, 2-alkenyl, 3-alkenyl or triorganosilyl radicals —SiR 3 , or amino radicals NR 2 wherein R stands for a C 1 to C 4 alkyl radical, R 3 denotes an optionally substituted C 1 to C 8 alkyl, C 5 to C 10 cycloalkyl, C 6 to C 14 aryl radical, or SiR 3 , or NR 2 wherein R has the aforementioned meaning, R 4 denotes (a) halogen selected from the group consisting of Cl, Br, and I, (b) NH—R 5 where R 5 =optionally substituted C 1 to C 8 alkyl, C 5 to C 10 cycloalkyl or C 6 to C 10 aryl radical, (c) O—R 6 where R 6 =optionally substituted C 1 to C 11 alkyl, C 5 to C 10 cycloalkyl or C 6 to C 10 aryl radical, (d) —SiR 3 , (e) BH 4 , (f) an optionally substituted allyl radical, (g) an indenyl radical, (h) optionally substituted benzyl radical, (i) an optionally substituted cyclopentadienyl radical, (j) —NR—NR′R″ (hydrazido(−1), wherein R, R′ and R″ mutually independently have the aforementioned meaning of R, (k) CH 2 SiMe 3 , (l) pseudohalide, or (m) silylamide —N(SiMe 3 ) 2 , R 7 and R 8 mutually independently denote H, optionally substituted C 1 to C 12 alkyl, C 5 to C 12 cycloalkyl or C 6 to C 10 aryl radicals.