How big is a Cp? Cycloheptatrienyl zirconium complexes with bulky cyclopentadienyl and indenyl ligands

Abstract

A combination of phase-transfer and traditional alkylation strategies has been employed to synthesise sterically encumbered 1,3-di(cyclohexyl) and 1,3-di(tert-butyl) substituted indenes in multi-gram quantities. These indenyl ligands and sterically demanding alkyl cyclopentadienyl ligands have been used to prepare a series of [(η(7)-C(7)H(7))Zr(η(5)-L)] (L = Cp and Ind) complexes by straightforward salt metathesis between [(η(7)-C(7)H(7))ZrCl(tmeda)] and the corresponding sodium indenide or cyclopentadienide. All of these Zr complexes have been characterized by elemental analysis, NMR spectroscopy and single crystal X-ray diffraction. The structural information derived from these studies was employed to evaluate the steric demand of these ligands in a realistic manner.

Cyclononatetraenyl‐Indenyl Transformation and a Zirconium(III) Trimer from Bulky Alkylcyclopentadienylzirconium Chlorides

“…Aided by a recent article on the steric bulk of substituted cyclopentadienyl ligands [13] the tetraalkylcyclopentadienyl ligand 2 2 Cp can be estimated to exert more steric bulk than the Cp* ligand C 5 Me 5 , which forms dimeric [Cp*ZrCl 3 ] 2 . Aided by a recent article on the steric bulk of substituted cyclopentadienyl ligands [13] the tetraalkylcyclopentadienyl ligand 2 2 Cp can be estimated to exert more steric bulk than the Cp* ligand C 5 Me 5 , which forms dimeric [Cp*ZrCl 3 ] 2 .…”

“…The gas purification system of the glove box keeps oxygen and water below 1 ppm. 13 C NMR shifts refer to the C 6 D 6 signal at δ = 128.1 ppm. Glassware was kept at 120°C overnight before being transferred into the box or used on the Schlenk line.…”

Diisobutylaluminum hydride-promoted cyclization of benzyl and phenylsilyl ethers bearing a 2-(trimethylsilyl)ethynyl group: syntheses of indenes and benzosiloles

“…3 Benzo[b]silole, a sila-analog of indene, is also an important motif to impart privileged optical and electronic properties to organic materials. 4 Much attention has been focused so far on efficient construction of these benzo-fuzed skeletons with regio-controlled introduction of substituents.…”

Bis(9,10-phenanthrenocyclopentadienyl)yttrium complexes: synthesis and solution behaviour

“…However, reactivity can also be hampered if the bulky groups project into the metallocene wedge in complexes of the type Cp' 2 LnR (Cp' = substituted Cp, Ln = Y or a lanthanide). 2 One solution to this potential problem is to increase effective steric bulk by fusing aromatic substituents to the Cp ring to create a flat deck ligand that does not impede access to the metallocene wedge.…”