Comparison of Doubly Lithiated, Magnesiated, and Zincated Ferrocenes: [Fe(η⁵-C₅H₄)₂]₂Zn₂(tmeda)₂, the First Example of a [1.1]Ferrocenophane with Bridging First-Row Transition Metal Atoms

Abstract

Starting from doubly lithiated ferrocene [Fe(η5-C5H4)2]3Li6(tmeda)2 (1), the corresponding thf adduct [Fe(η5-C5H4)2]2Li4(thf)6 (3) was prepared by recrystallization of 1 from thf. In contrast to 1, which features six Li+ cations surrounded by 1,1′-ferrocenediyl fragments in a carousel arrangement, compound 3 contains only two ferrocenediyl anions bridged by four Li+ cations. This comparison clearly reveals the strong impact of different supporting ligands on the solid-state structures of lithiated ferrocenes. The doubly magnesiated and zincated derivatives [Fe(η5-C5H4)2]3Mg3(tmeda)2 (4) and [Fe(η5-C5H4)2]2Zn2(tmeda)2 (6) were synthesized via salt metathesis using 1 and MgCl2 or ZnCl2, respectively. Even though Mg2+ and Zn2+ are chemically related ions, the solid-state structures of 4 and 6 turned out to be distinctly different. Compound 4 possesses a cluster structure reminiscent of the lithiated aggregate 1, whereas 6 represents the first example of a first-row transition metal-bridged [1.1]-ferrocenophane (anti-conformation). All three doubly metallated ferrocenes 3, 4, and 6 are suitable reagents for the preparation of 1,1′-disubstituted ferrocenes as has been exemplified for the synthesis of Fe(η5-C5H4SiMe3)2 (5). We have also shown that 5 can be generated in yields exceeding 90% from Fe(η5-C5H4Br)2, Me3SiCl, and Rieke magnesium.

The Crystal Structure of the THF Adduct of Monolithioferrocene

“…The thf adduct of monolithioferrocene crystallizes as [Fe(η 5 ‐C 5 H 4 )(η 5 ‐C 5 H 5 )] 2 Li 2 (thf) 4 in the monoclinic space group P 2 1 featuring Li 2 C 2 four‐membered rings. Together with the solid‐state structure of the thf adduct of dilithiated ferrocene [Fe(η 5 ‐C 5 H 4 ) 2 ] 2 Li 4 (thf) 6 reported by Wagner 16 the two probably most often employed lithiated ferrocenes are now structurally characterized.…”

“…The solid‐state structures of the tmeda and pmdta adducts of 1, 1'‐dilithiated ferrocene (tmeda = N , N , N' , N' ‐tetramethylethane‐1, 2‐diamine,15a pmdta = N , N , N' , N' , N'' ‐pentamethyldiethylenetriamine15b) have been reported as well. The tetrahydrofuran adduct [Fe(η 5 ‐C 5 H 4 ) 2 ] 2 Li 4 (thf) 6 has been prepared and structurally characterized by Wagner 16. Basically, all 1, 1'‐dilithiated ferrocenes display a central Li 2 C 2 four‐membered ring and two terminal base‐coordinated lithium cations.…”

Alkali and alkaline-earth metals

“…144 Starting from doubly lithiated ferrocene [Fe(Z 5 -C 5 H 4 ) 2 )] 3 Li 6 (TMEDA) 2 , the corresponding THF adduct was prepared by recrystallisation from THF. 145…”

Cyclic and Linear Polyferrocenes with Silicon and Tin as Alternating Bridges

“…The first anti isomer of a dicarba[1.1]ferrocenophane was structurally characterized a few decades later 9. Since the synthesis of the first [1.1]FCPs in 1956,7 this family of compounds has grown significantly with the incorporation of B,10 Al,11 Ga,11b, 12 In,11b, 13 Si,14 Sn,15 Pb,16 P,17 As,18 S,19 Zn,20 and Hg21 atoms as heteroatom bridges. In addition to these [1.1]FCPs, other [1.1]metallacyclophanes have been synthesized, such as [1.1]ruthenocenophanes,14a, 22 [1.1]chromarenophanes,23 [1.1]molybdarenophanes,23 and mixed [1.1]metallacyclophanes22 that contained Fe/Ru or Fe/Co metal combinations.…”