Transition metal complexes of sterically demanding cyclopentadienyl ligands

Synthesis and Characterization of Osmium(II) Compounds of Stoichiometry (C5Me5)OsL2Br, (C5Me5)OsL2H, and (C5Me5)Os(NO)Br2

“…Interestingly, the 13 C{ 1 H) NMR resonance due to the C 5 Me 5 ring carbons in 2 becomes markedly broadened at −80 °C while the C 5 Me 5 methyl resonance remains sharp. This behavior is indicative of slowed rotation of the C 5 Me 5 ring, a phenomenon observed only rarely in solution. − The sharpness of the ring methyl resonance presumably reflects the smaller chemical shift dispersion for these carbons.…”

Titanocene and Zirconocene Complexes containing Dendrimer-Substituted Cyclopentadienyl Ligands − Synthesis and Ethylene Polymerization

“…[2] However, some degree of stereocontrol is in principle possible without a rigid ligand framework if rotation of the Cp ligands is hindered, [3] for example by means of sterically demanding substituents. [4] We are currently studying the chemistry of titanium and zirconium metallocenes located at the focal point of one or two dendritic wedges. Our interest is focused on their use as precursors for olefin polymerization.…”

1,1′,2,2′-Tetralithioferrocene and 1,1′,2,2′,3,3′-Hexalithioferrocene: Useful Additions to Ferrocene Precursor Compounds

“…The 1 H NMR spectrum of compound 11 provided conclusive verification with the characteristic doublet and triplet patterns as observed for 1 , except the doublet is upfield of the triplet in this case, which is similar to the NMR spectrum of 1,1′,2,2′-tetrakis­(tri- n -butylstannyl)­ferrocene. The new synthetic method provides a new isomer (Scheme A) in comparison to the 1,1′,3,3′-isomer 14 , which had been previously been prepared by Okuda and co-workers − (Scheme B). The reaction of 1,1′,2,2′,3,3′-hexabromoferrocene with tert -butyllithium at temperatures below −50 °C in THF gave the corresponding hexalithioferrocene in situ , and when this compound was reacted with chlorotrimethylsilane, it gave the 1,1′,2,2′,3,3′-hexasilylferrocene (Figure ) initially as a deep red oil which crystallized from methanol as red needles in an isolated yield of ca.…”