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Reactions of Lactams with Titanocene‐ and Zirconocene‐Alkyne Complexes as Elemental Steps in Catalytic Anionic Ring‐Opening Polymerization of Lactams
Author(s) -
Arndt Perdita,
Lefeber Claudia,
Kempe Rhett,
Tillack Annegret,
Rosenthal Uwe
Publication year - 1996
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19961291022
Subject(s) - chemistry , agostic interaction , alkyne , metallocene , deprotonation , trimethylsilyl , medicinal chemistry , ring opening polymerization , polymer chemistry , acetylene , polymerization , stereochemistry , catalysis , metal , organic chemistry , ion , polymer
Depending on the nature of the metal and the ring size, lactams react with titanocene and zircocene complexes of bis‐(trimethylsilyl)acetylene 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)(Me 3 SiC 2 SiMe 3 ) with N ‐methyl‐€‐caprolactam a simple ligand exchange reaction occurs and the complex Cp 2 Zr(Me 3 SiC 2 SiMe 3 )[OH 2 ) 5 ] ( 1 ) was isolated. With β‐propiolactam the alkenyl‐amido complex Cp 2 )(SiMe 3 )][–NH 2 ] ( 2 ) was obtained, which indicates that an agostic metal‐hydrogen interaction has taken place. The reaction of Cp 2 Ti(Me 3 ‐SiC 2 SiMe 3 ) with €‐caprolactam gives after elimination of the alkyne and molecular hydrogen the first early transition metal complex with a deprotonated coordinated €‐caprolactam in a η 2 ‐amidate bonding fashion ( 3 ). The obtained complexes were characterized by NMR spectra ( 1, 2 ) and crystal structure analysis ( 1–3 ) and discussed as elemental steps in anionic ring‐opening polymerization of lactams catalyzed by metallocene‐alkyne complexes.