Jesús Cano

Allylsilylcyclopentadienyl Group 4 metal complexes: synthesis, structure and reactivity

Financial support of our work by MCyT (Project MAT2001-1309) is gratefully acknowledged. G.H., G.M and J.C are grateful to to the Alexander von HumboldtStiftung, MEC and CAM for fellowships.

Cis- and trans-titanium complexes with doubly silyl-bridged dicyclopentadienyl ligands: molecular structure of [(TiCl)2 (μ-0) {(SiMe2)2(η5-C5H3)2}]2 (μ-O)2

The reaction of TiCl 4 with Li 2 [(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 ] in toluene at room temperature afforded a mixture of cis - and trans -[(TiCl 3 ) 2 {(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] in a molar ratio of after recrystallization. The complex trans -[(TiCl 3 ) 2 {(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] was hydrolyzed immediately by the addition of water to THF solutions to give trans -[(TiCl 2 ) 2 ( μ -O){(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] as a solid insoluble in all organic solvents, whereas hydrolysis of cis -[(TiCl 3 ) 2 {(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] under different conditions led to the dinuclear μ-oxo complex cis -[(TiCl 2 ) 2 )( μ -O){(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] and two oxo complexes of the same stoichiometry [(TiCl) 2 ( μ -O){(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] 2 ( μ -O) 2 as crystalline solids. Alkylation of cis - and trans -[(TiCl 3 ) 2 {(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] with MgCIMe led respectively to the partially alkylated cis -[(TiMe 2 Cl) 2 {(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] and the totally alkylated trans -[(TiMe 3 ) 2 {(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] compounds. The crystal and molecular structure of the tetranuclear oxo complex [(TiCl) 2 ( μ -O){(SiMe 2 ) 2 ( η 5 -C 5 H 3 ) 2 }] 2 ( μ -O) 2 was determined by X-ray diffraction.

Cyclopentadienyl-based Mg complexes in the intramolecular hydroamination of aminoalkenes: mechanistic evidence for cationic versus neutral magnesium derivatives

Neutral and cationic magnesium complexes stabilized by coordination of a cyclopentadienyl ligand with two different neutral hemilabile donor groups [Mg{η5-C5H3-1,3-(CH2CH2NiPr2)(SiMe2NPh2)}X(thf)] (X = Bz (2); N(SiMe3)2 (3)) and [Mg{η5-C5H3-1,3-(CH2CH2NiPr2)(SiMe2NPh2)}][BPh4] (4) have been prepared and characterized. The 1H-13C HMBC and HSQC spectra of compounds 2 and 3 demonstrate the formation of 1,3-substituted cyclopentadienyl compounds and DOSY and 1H-NMR experiments support the coordination–decoordination in solution of a THF molecule in complex 2. No Schlenk-type ligand redistributions were observed in the chemical behaviour of these magnesium complexes. Compounds 2–4 are active catalysts in the hydroamination of aminoalkenes; stoichiometric reactions and kinetic measurements have been performed to gain an insight into their reaction mechanisms. A key contribution here is the catalytic reactivity of a cationic magnesium compound.