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Untypical Regioselectivity of Carbon Dioxide Coupling with Titanocene Complexes of Phenyl(trimethylsilyl)acetylene by Using the meso ‐1,2‐Ethylene‐1,1′‐bis(η 5 ‐tetrahydroindenyl) Ligand System
Author(s) -
Thomas Dominique,
Peulecke Normen,
Burlakov Vladimir V.,
Baumann Wolfgang,
Spannenberg Anke,
Kempe Rhett,
Rosenthal Uwe
Publication year - 1998
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(199810)1998:10<1495::aid-ejic1495>3.0.co;2-d
Subject(s) - chemistry , regioselectivity , alkyne , trimethylsilyl , ethylene , acetylene , medicinal chemistry , silylation , ligand (biochemistry) , crystal structure , steric effects , stereochemistry , crystallography , organic chemistry , catalysis , biochemistry , receptor
The reaction of [ meso ‐(ebthi)TiCl 2 ] [ebthi = 1,2‐ethylene‐1,1′‐bis(η 5 ‐tetrahydroindenyl)] with magnesium in the presence of the alkynes Me 3 SiC≡CSiMe 3 and PhC≡CSiMe 3 resulted in the formation of the complexes [ meso ‐(ebthi)Ti(η 2 ‐Me 3 SiC 2 SiMe 3 )] ( 1 ) and [ meso ‐(ebthi)Ti(η 2 ‐PhC 2 SiMe 3 )] ( 2a and 2b ), which were isolated and then characterized by their NMR spectra. Due to incomplete reduction the Ti III complex [ meso ‐(ebthi)Ti(THF)Cl] ( 3 ) was also obtained as a by‐product of these reactions. By insertion into the Ti–CPh bond carbon dioxide reacted with the titanacyclopropene structure of the alkyne complex [ meso ‐(ebthi)Ti(η 2 ‐PhC 2 SiMe 3 )] ( 2a ), with untypical regioselectivity to yield the α‐silyl‐substituted meso ‐(ebthi)titanafuranone 6a . In the analogous reactions of the complexes [(thi) 2 Ti(η 2 ‐PhC 2 SiMe 3 )] (thi = η 5 ‐tetrahydroindenyl), [ rac‐ (ebthi)Ti(η 2 ‐PhC 2 SiMe 3 )], and [Cp* 2 Ti(η 2 ‐PhC 2 SiMe 3 )] with carbon dioxide typical regioselectivity (insertion into the M–CSi bond of the titanacyclopropene) was observed, yielding the β‐silyl‐substituted titanafuranones 7 , 8a , and 9 . These results show that insertion of carbon dioxide into the M–C bond of the titanacyclopropene structure of the alkynemetallocene complexes is governed by the substitution pattern of the alkyne and the steric enviroment around the metal center. The complexes 3 , 6a , and 7 were investigated by X‐ray crystal structure analysis.