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Preparation and Characterization of Half‐Sandwich (Pentamethylcyclopentadienyl)(triflato)titanium(IV) Complexes: Solid‐State Structural Motifs and Catalysis Studies
Author(s) -
Ngo Silvana C.,
Toscano Paul J.,
Welch John T.
Publication year - 2002
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(200210)85:10<3366::aid-hlca3366>3.0.co;2-y
Subject(s) - chemistry , methylaluminoxane , trifluoromethanesulfonate , polystyrene , monomer , titanium , catalysis , steric effects , styrene , polymerization , polymer chemistry , tacticity , crystallography , stereochemistry , metallocene , copolymer , organic chemistry , polymer
Half‐sandwich (pentamethylcyclopentadienyl)(triflato)titanium(IV) complexes of the type [Ti(Cp*)(TfO) 2 X] (X=MeO ( 1 ), Me ( 2 ), 2,4,6‐Me 3 C 6 H 2 O ( 5 )) or [Ti(Cp*)( o ‐OC 6 H 4 O)(TfO)] ( 7 ) were readily synthesized via methathesis of the corresponding chloride complexes with silver triflate (Cp*=( η 5 ‐1,2,3,4,5‐pentamethylcyclopenta‐2,4‐dien‐1‐yl)). In addition, the complex 3 with X=OH was prepared by controlled hydrolysis of 2 . The solid‐state structures of these new complexes were determined by single‐crystal X‐ray‐diffraction techniques. Three different structural motifs were identified; 1, 2, 3 , and 7 are dimeric, while 5 is monomeric. The complexes were screened for their ability to stereospecifically polymerize styrene under homogeneous conditions. In the absence of activators, such as MAO (methylaluminoxane), 1 and 2 readily catalyzed the formation of atactic polystyrene; a strong dependence on the steric size of X was noted. In the presence of MAO, all of the complexes showed high activity and strong preference for the synthesis of syndiotactic polystyrene that was superior to that of [TiCl 3 (Cp*)]/MAO.