Early transition metal and lanthanide metallocenes bearing dihydroazulenide ligands

Dihydroguaiazulenide Complexes and Catalysts of Group 8–12 Transition Metals: Ligands from Renewable Feedstock Replace, even Outmatch Petrochemical Based Cyclopentadienyl Chemistry

“…The authors used this reagent cocktail containing both regio isomers and not separated aluminium hydrides in the synthesis of a stereoisomeric mixture of metallocene dichlorides of titanium and zirconium, specifically early transition metal compounds difficult to reduce by present aluminium hydride side products. [18] Sugano et al used a carbolithiation approach in their design of -SiMe 2 -bridged ansa-metallocenes from PhLi and 2-methyl azulenes. [16,[19][20][21] To the best of our knowledge, no further reports on organometallic chemistry of AzuH or GuaH, no XRD characterization of any AzuH and GuaH complexes, and no explicit NMR spectroscopic proof for the isolation of only one isomer of AzuH or GuaH complexes has been published up to date.…”

“…Only recently, Edelmann and coworkers prepared a mix of (GuaH)Li isomers in situ from guaiazulene (Gua) and excess of LiAlH 4 . The authors used this reagent cocktail containing both regio isomers and not separated aluminium hydrides in the synthesis of a stereoisomeric mixture of metallocene dichlorides of titanium and zirconium, specifically early transition metal compounds difficult to reduce by present aluminium hydride side products [18] . Sugano et al.…”

“… Rare examples of literature‐known 8‐ H and 8‐organo‐dihydroazulenyl complexes obtained as mix of isomers [14,16–21] …”

Catalytic Hydrolithiation of Guaiazulene: Isolation of Two Isomerically Pure Renewable Feedstock‐Based Cyclopentadienyl Synthons

“… [24,26] This highly reducing carbanionic building block has never been isolated and fully characterized by elemental analysis, spectroscopy and XRD analysis. To the best of our knowledge, ligand transfer reactions of (Gua”)Na to less electropositive metals have never been accomplished [20a] …”

“…A drawback of Hafners carbolithiation approach in transition metal chemistry is however, that these only in situ prepared lithium 8‐ and 6‐organo‐dihydroazulenide mixtures (AzuR)Li or (GuaR)Li are leading to a highly complex non‐separable mixture of regio‐ and stereoisomers ‐ a consequence of the combination of planar‐chiral and C 1 symmetry elements in one transition metal π complex [20a,25] …”