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Chemistry of new electrophilic metal ALKYL compounds
Author(s) -
Crowther Donna J.,
Jordan Richard F.
Publication year - 1993
Publication title -
makromolekulare chemie. macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 0258-0322
DOI - 10.1002/masy.19930660112
Subject(s) - chemistry , metallocene , electrophile , agostic interaction , reactivity (psychology) , cationic polymerization , medicinal chemistry , alkyl , metal , stereochemistry , carborane , methylene , methylaluminoxane , polymerization , polymer chemistry , catalysis , organic chemistry , medicine , polymer , alternative medicine , pathology
The reaction of the neutral carborane C 2 B 9 H 13 with Cp*M(CH 3 ) 3 (M = Zr (a), Hf (b); Cp* = η 5 ‐C 5 Me 5 ) yields [Cp(C 2 B 9 H 11 )M(CH 3 )] n (3a, b). Complexes 3a, b form THF adducts Cp*(C 2 B 9 H 11 )M(CH 3 )(THF) 4, insert 2‐butyne to yield Cp*(C 2 B 9 H 11 )M{C(Me=CMe 2 } 5, and undergo methane elimination upon thermolysis to yield methylene‐bridged complexes [Cp*(C 2 B 9 H 11 )M] 2 (μ‐CH 2 ) (6). These chemical studies, and companion structural and theoretical studies establish that 3a, b are neutral analogues of the cationic Cp 2 M(R) + species (1; Cp = η 5 ‐C 5 H 5 ) and Cp 2 M(R)(L) + (2) which are believed to be active in Cp 2 MX 2 ‐based Ziegler catalysts. Despite the lower metal charge, 3–6 exhibit characteristic “electrophilic metal alkyl” properties including agostic M‐H‐C and M‐H‐B interactions, high insertion and intramolecular C‐H activation reactivity, and high ethylene polymerization and propene oligomerization activity. These observations suggest that the key requirement for high insertion/polymerization activity in metallocene systems is high metal unsaturation (i.e. two empty metal‐centered orbitals) rather than charge.