Carbonyl-Substituted Nickelocenes by the Cross-Metathesis Route

Abstract

Ru(II)-catalyzed cross-metathesis of 1,1′-diallylnickelocene (1) with methyl vinyl ketone or methyl acrylate afforded in high yields 1,1′-bis(4-oxo-2-pentenyl)nickelocene (3) or 1,1′-bis(4-methoxy-4-oxo-2-butenyl)nickelocene (4), respectively. Compound 3 crystallizes in the monoclinic crystal system, space group P21 /c, in a staggered conformation with the α,β-unsaturated moiety perpendicular to the cyclopentadienyl plane.

Axial chiral metallocenes by two-fold ring-closing metathesis

“…3 We have shown that 1,1′-bis-(alkenyl) derivatives of this moderately stable metallocene are viable substrates for the ruthenium-catalyzed alkene metathesis reactions yielding strained ansa-nickelocenes 4 or ring-substituted nickelocenes. 5 Bent metallocene derivatives are of great potential interest in catalysis because the non-planar arrangement of ligands may expose the metal centre to the incoming substrate. 6 We anticipated that nickelocene derivative 1 7 (Scheme 1) bearing four alkenyl substituents might undergo two-fold ring-closing metathesis to yield an unprecedented, rigid sandwich complex, 8,9 with a considerable tilt angle.…”