Syntheses, Characterization, and Multifaceted Coordination Chemistry of Hydrazonido Titanium Complexes

Abstract

The reaction of hydrazones with bis(π−η 5 :σ−η 1pentafulvene)titanium complexes leads to both hydrazonido and hydrazido complexes depending on the interaction of the hydrazone with the fulvene ligand of the metal complex. The molecular structures mostly reveal κ 2 N,N side-on coordination of the hydrazonido ligand due to the deprotonation of the N−H bond by one of the fulvene moieties. Instead of deprotonation, the reaction of the bis(adamantylidene fulvene)titanium complexes with cinnamon aldehyde phenylhydrazone leads to κ 1 N coordination. By using donating groups in the backbone of the hydrazone ligands, there are exceptions to this coordination mode due to the insertion of the C�N double bond into the Ti−C exo bond of the pentafulvene moiety. Using 2-pyridinecarboxaldehyde phenylhydrazone, a formal κ 3 N,N,N ligand system is formed by the coordination of the pyridine nitrogen atom to the metal center via consecutive N−H deprotonation and insertion. Finally, the use of salicylaldehyde phenylhydrazone ultimately produces a complex with the κ 3 N,N,O coordination mode by double deprotonation of the hydrazone N−H and O−H functions. Because of its slow conversion to the final product, the intermediate was isolated as an insertion product with consecutive O−H deprotonation, showing a κ 2 N,O coordination mode of the hydrazido ligand.

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

“… 5 , 38 − 40 Because the chemistry of bis(π–η 5 :σ–η 1 -pentafulvene)titanium complexes is characterized by a broad range of E–H activation and Ti–C functionalization reactions, 41 they are excellent precursors for the generation of bimetallic Ti/Fe complexes. 42 , 43 As we reported earlier, 44 both monofunctional and bifunctional transformations are possible depending on the substrate. Herein, we report novel bimetallic Ti/Fe complexes based on ferrocene aldehydes, ketones, alcohols and 1,1′-bis(phenylphosphine)ferrocene.…”

“…The synthesis and applications of heterobimetallic complexes are an ever-present topic in inorganic chemistry. − Of particular interest is the incorporation of ferrocene derivatives into other metal complex frameworks. − Since the discovery of ferrocene and its formerly unprecedented sandwich-structure, , many ferrocene derivatives have been reported. − Because of the manifold derivatization options of the ferrocene framework, there is a huge number of polymetallic complexes containing ferrocenes which are linked with different bridges (C; − N; − O; − P; S; , Se; , N,O ,, ). In the context of ferrocene-based titanium complexes, several studies have focused on clusters, − electron-deficient catalysts , and redox-active compounds. ,− Because the chemistry of bis­(π–η 5 :σ–η 1 -pentafulvene)titanium complexes is characterized by a broad range of E–H activation and Ti–C functionalization reactions, they are excellent precursors for the generation of bimetallic Ti/Fe complexes. , As we reported earlier, both monofunctional and bifunctional transformations are possible depending on the substrate. Herein, we report novel bimetallic Ti/Fe complexes based on ferrocene aldehydes, ketones, alcohols and 1,1′-bis­(phenylphosphine)­ferrocene.…”