Syntheses, Characterization, and Redox Activity of Ferrocene-Containing Titanium Complexes

The chemistry of bis(pi-eta(5):sigma-eta(1)-pentafulvene)titanium complexes is characterized by a broad range of E-H activation and Ti-C functionalization reactions, whereas ferrocene derivatives are easily accessible and redox-active compounds. The reaction of ferrocenealdehyde and -ketones with bis(pi-eta(5):sigma-eta(1)-pentafulvene)titanium complexes result in the formation of bimetallic complexes via insertion of the C=O double bond of the aldehyde/ketone into the Ti-C-exo bond of the pentafulvene moiety. The reaction of bis(pi-eta(5):sigma-eta(1)-pentafulvene)titanium complexes with ferrocenyl alcohols leads to alcoholate complexes via deprotonation of the OH group by the pentafulvene ligand. Because of the one remaining pentafulvene unit, further functionalization of the complexes is possible. In this work, we proceeded with 1,1 '-bifunctionalized ferrocene derivatives for intramolecular follow-up reactions. 1,1 '-Ferrocenedimethanol reacts with bis(pi-eta(5):sigma-eta(1)-pentafulvene)titanium complexes in a double O-H deprotonation reaction to yield the dialcoholate complex. 1,1 '-bis(phenylphosphine)ferrocene reacts differently as the double P-H deprotonation reaction results in the formation of a P-P linked phosphine. Therefore, we studied the reactivity of 1,1 '-bis(phenylphosphine)ferrocene toward Rosenthal's reagent. As Rosenthal's reagent is regarded as a masked titanocene(II) species, it undergoes redox reactions toward H-acidic substrates, forming a paramagnetic Ti(III) complex.