ansa-Nickelocenes by the Ring-Closing Metathesis Route:  Syntheses, X-ray Crystal Structures, and Physical Properties

Abstract

The first ansa-nickelocenes, [Ni(η 5 ,η 5 -C 5 H 4 -CH 2 -CHdCH-CH 2 -C 5 H 4 )] ( 4) and [Ni(η 5 ,η 5 -C 5 H 4 - 6), were prepared by alkene metathesis of 1,1′-disubstituted nickelocenes. Compound 4 reacts with hydrogen to yield ansa-nickelocene 7, bearing the saturated bridge. The new compounds were characterized by UV-vis, IR, MS, 1 H NMR, magnetic susceptibility, and electrochemical measurements. Crystal and molecular structures of 4, 6, and 7 were determined by single-crystal X-ray analysis. These measurements show that the studied ansa-nickelocenes exhibit properties similar to those of nickelocene.

Ring‐Opening Polymerisation of Low‐Strain Nickelocenophanes: Synthesis and Magnetic Properties of Polynickelocenes with Carbon and Silicon Main Chain Spacers

“…Paramagnetic 1 H NMR spectroscopy revealed α and β cyclopentadienyl resonances at −251.2 and −256.6 ppm, respectively, an α‐CH 2 resonance at 138.2 ppm, and a β‐CH 2 resonance at −1.1 ppm (Figure S1). These signals in the 1 H NMR spectrum are consistent with those previously reported . Although the crystallographic data in the original report were not provided in full due to poor refinement, in this case crystallisation from n ‐hexanes yielded dark green crystals which allowed for full characterisation by single‐crystal X‐ray diffraction (Figure )…”

“…To provide an interesting comparison we explored the polymerisation of tetracarba[4]nickelocenophane 8 . This species has previously been prepared via the ring‐closing metathesis of a divinyl substituted nickelocene followed by a subsequent hydrogenation . In our work the synthesis of 8 was conducted via an analogous fly trap synthesis to that employed for the tricarba analogue 5 , involving the reaction of the dilithiated ligand Li 2 [(C 5 H 4 ) 2 (CH 2 ) 4 ] and NiCl 2 (see Supporting Information).…”

New cyclic and macrocyclic silaolefins via ring-closing metathesis of 1,1-bis(silyl)ethene-tethered dienes

“…Detailed GCMS studies have shown, that after preliminary formation of the 9-or 11-membered carbosilane derivatives, their further metathetical cyclodimerization took place (Scheme 3). Such a cyclodimerization of dialkenylsubstituted organometallic reagents under RCM conditions has been previously reported for dialkenylsilanes [31] and more recently for bis(alkenyl)niclocenes [32]. Reactions of 4 with ruthenium-benzylidene catalyst in CH 2 Cl 2 after 2 h gave an equilibrium mixture including the substrates, 9-membered carbosilane and cyclodimer isomers in the ratio 44:31:25 (Fig.…”

Tin-Bridgedansa-Metallocenes of the Late Transition Metals Cobalt and Nickel: Preparation, Molecular and Electronic Structures, and Redox Chemistry

“…Intramolecular ring-closing olefin metathesis was used to construct the first structurally characterized ansa-nickelocenes (IV), 6 in which an unsaturated carbon bridge connects the two cyclopentadienyl fragments. 7 Interestingly, the bridge is readily converted into its saturated analogue by hydrogenation, without affecting the π system of the Cp ligands. 8 In another approach, the so-called flytrap method, 3 which involves the reaction of dianionic bis(cyclopentadienyl) ligand sets with appropriate metal halides, the Manners group synthesized two hydrocarbon-bridged [n]cobaltocenophanes (III; n = 2, 3) with varying lengths of the bridge.…”