Early transition metal complexes of carbene donors linked to cyclopentadienyl ring analogues or amidine/amidinate moieties

• Main Author: Conde Guadano, Susana
• Other Authors: Danopoulos, Andreas A.
• Published: University of Southampton 2010
• Subjects: 547.05; QD Chemistry
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.539072

The new indenyl-functionalised NHC potassium salt, 1-[3-(4, 7-dimethylindenylpropyl]-3- (2,6-diisopropylphenyl)imidazol-2-ylidenepotassium, has been synthesised. Complexes of titanium, zirconium and chromium containing this ligand and the two carbon bridge analogue, 1-[2-(4,7-dimethylindenyl)ethyl]-3-(2,6-diisopropylphenyl)imidazol-2 ylidene potassium, have been synthesised and characterised by X-ray crystallographic techniques. The following complexes were tested as catalysts for the oligomerisation of ethylene in the presence of MAO: 3-(2,6-diisopropylphenyl)-1-[2-(4,7-dimethylindenyl)ethyl]-imidazol-2-ylidene(tertbutylimido) titanium chloride, 3-(2,6-diisopropylphenyl)-1-[3-(4,7- dimethylindenyl)propyl]imidazol-2-ylidene(tert-butylimido)titanium chloride, 3-(2,6- diisopropylphenyl)-1-[3-(4,7-dimethylindenyl)propyl]imidazol-2-ylidenezirconium trichloride, 3-(2,6-diisopropylphenyl)-1-[2-(4,7-dimethylindenyl)ethyl]imidazol-2- ylidenezirconium trichloride, 3-(2,6-Diisopropylphenyl)-1-[2-(4,7-dimethylindenyl)ethyl]- imidazol-2-ylidenechromium dichloride, 3-(2,6-diisopropylphenyl)-1-[3-(4,7- (dimethylindenyl)propyl]imidazol-2-ylidene chromium dichloride, 3-(2,6-diisopropylphenyl)- 1-[3-(4,7-dimethylindenyl)propyl]-imidazol-2-ylidene chromium methyl chloride and 3-(2,6- diisopropylphenyl)-1-[2-(4,7-dimethylindenyl)ethyl]-imidazol-2-ylidenevanadium dichloride. The following alkyl chromium complexes containing 1-[2-(4,7-dimethylindenyl)ethyl]-3-(2,6- diisopropylphenyl)imidazol-2 ylidene potassium have also been synthesised: 3-(2,6- diisopropylphenyl)-1-[2-(4,7-dimethylindenyl)ethyl]-imidazol-2-ylidene chromium phenyl chloride and 3-(2,6-diisopropyl-phenyl)-1-[2-(4, 7-dimethylindenyl)ethyl]-imidazol-2-ylidene chromium dibenzyl. Chromium cations have been synthesised using as starting materials the chromium alkyl complexes. The Cr(II) complex 3-(2,6-diisopropyl-phenyl)-1-[2-(4, 7- dimethylindenyl)ethyl]-imidazol-2-ylidene chromium monochloride and a partially oxidised dimerised product were also isolated. 5-(2-chloroethyl)- 1, 2, 3, 4-tetramethylcyclopentadiene and 5-(3-chloropropyl) 1, 2, 3, 4-tetramethylcyclopentadiene were synthesised and isolated as geminal isomers for the first time. The trialkyl chromium complex, tribenzyl chromium tris(tetrahydrofuran) was synthesised and also it was used as starting material for the complexes di(benzyl)chromium bis(1, 3- diisopropylimidazol-2-ylindene) and tri(benzyl)chromium TACN. All complexes were characterised by X-ray crystallography. The imidazolium salt 3-(2.6-diisopropylphenyl)-1-[N, N-bis(2,6- diisopropylphenyl)acetamidyl] imidazolium chloride was synthesised and used as a precursor for the synthesis of amidinate-functionalised NHC zirconium and amidine-functionalised NHC silver complexes. Double deprotonation of 3-(2,6-diisopropylphenyl)-1-[N, N’-bis(2,6- diisopropylphenyl)acetamidyl] imidazolium chloride gave the amidinate-functionalised NHC ligand, 3-(2.6-diisopropylphenyl)-1-[2-N, N’bis(2,6 diisopropylphenylamidinate)ethyl]imidazol-2-ylidenepotassium. Titanium, zirconium and chromium complexes containing this ligand were synthesised and characterised by X-ray crystallographic techniques. Transmetallation of the amidine-functionalised NHC silver complex with [Rh(COD)Cl]2 and [Ir(COD)Cl]2 gave the corresponding species. Rh(amidinefunctionalised NHC)(COD)Cl reacted with Na(BAr)4 (Ar = 3,5-CF3C6H3) to give the cation Rh(amidine-functionalised NHC)(COD)]+[BAr4]-. These species were also characterised by X-ray diffraction techniques.