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Reactions of Functional Groups at the Periphery of Group 4 Metallocene Frameworks: Selective Formation of a Cp‐Bonded Azaboretidine Derivative by a Hydroboration Route
Author(s) -
Kunz Doris,
Erker Gerhard,
Fröhlich Roland,
Kehr Gerald
Publication year - 2000
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(200003)2000:3<409::aid-ejic409>3.0.co;2-6
Subject(s) - hydroboration , chemistry , metallocene , borane , deprotonation , medicinal chemistry , diastereomer , stereochemistry , adduct , ligand (biochemistry) , electrophilic addition , electrophile , polymerization , catalysis , organic chemistry , polymer , ion , biochemistry , receptor
6‐Amino‐6‐methylfulvene has been coupled with benzoic acid by treatment with 7‐azahydroxybenzotriazole and DCC. Subsequent two‐fold deprotonation, at the NH and 6‐methyl groups, generated the vinylidene‐bridged Cp/benzoylamido ligand 5 . Treatment of 5 with ZrCl 4 (THF) 2 gave the spiro ‐metallocene complex 3a (characterized by X‐ray crystal structure analysis), while reaction of 5 with (Et 2 N) 2 ZrCl 2 (THF) 2 yielded the bridged half‐sandwich complex 3b . Treatment of 3a with two molar equivalents of the strongly electrophilic borane HB(C 6 F 5 ) 2 resulted in hydroboration of the exocyclic CC double bond with concomitant intramolecular N–B adduct formation to yield the azaboretidine‐type systems 7 (three diastereoisomers, one of which has been characterized by X‐ray diffraction analysis). Similarly, hydroboration of 3b with HB(C 6 F 5 ) 2 yielded the azaboretidine derivative 9 . Activation of the complexes 7 and 9 with methylalumoxane led to active homogeneous Ziegler‐type propene polymerization catalysts.