REACTIONS OF LACTAMS WITH TITANOCENE-ALKYNE AND ZIRCONOCENE-ALKYNE COMPLEXES AS ELEMENTAL STEPS IN CATALYTIC ANIONIC RING-OPENING POLYMERIZATION OF LACTAMS

Depending on the nature of the metal and the ring size, lactams react with titanocene and zircocene complexes of bis(trimethylsilyl)acetylen e Cp(2)Ti(Me(3)SiC(2)SiMe(3)) and Cp(2)Zr(L)(Me(3)SiC(2)SiMe(3)) (L = Py, THF) to yield different products. In the reaction of Cp(2)Zr(Py)(M e(3)SiC(2)SiMe(3)) with N-methyl-epsilon-caprolactam a simple ligand e xchange reaction occurs and the complex Cp(2)Zr(Me(3)SiC(2)SiMe(3))[O = C-N(Me)-(CH2)(5)] (1) was isolated. With beta-propiolactam the alken yl-amido complex Cp(2)Zr[-C(SiMe(3)) = C(H)(SiMe(3))][-N-CO-CH2-CH2] ( 2) was obtained, which indicates that an agostic metal-hydrogen intera ction has taken place. The reaction of Cp(2)Ti(Me(3)-SiC(2)SiMe(3)) wi th epsilon-caprolactam gives after elimination of the alkyne and molec ular hydrogen the first early transition metal complex with a deproton ated coordinated epsilon-caprolactam in a eta(2)-amidate bonding fashi on Cp(2)Ti-O-C-N-(CH2)(5) (3). The obtained complexes were characteriz ed by NMR spectra (1, 2) and crystal structure analysis (1-3) and disc ussed as elemental steps in anionic ring-opening polymerization of lac tams catalyzed by metallocene-alkyne complexes.