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

The first ansa-nickelocenes, [Ni(η5,η5-C5H4−CH2−CHCH−CH2−C5H4)] (4) and [Ni(η5,η5-C5H4−(CH2)2−CHCH−(CH2)2−C5H4)] (5), and a bridged binickelocene, [Ni2(η5,η5-C5H4−(CH2)2−CHCH−(CH2)2−C5H4)2] (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, 1H 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.