Unexpected Formation and Structural Characterization of a Dinuclear Sodium Half-Sandwich Complex

Abstract

Treatment of N,N-diisopropylcarbodiimide with sodium cyclopentadienide (NaCp) in a molar ratio of 1:1 in THF solution resulted in formation of the unexpected dinuclear sodium half-sandwich complex [NaC 5 H 3 {C(NH i Pr)(=N i Pr)} 2-1,2] 2 (1) as colorless crystals in low yield. The newly formed ligand, which belongs to the group of 6-aminofulvene-2-aldiminate ligands, coordinates to sodium in an η 5-coordination mode via the cyclopentadienyl ring. Dimerization occurs through additional chelating κN,N-coordination of the amidine substituents. The NMR data of 1 indicated a slow dimer/monomer equilibrium in solution. A serendipitously isolated hydrolysis product, {µ-(i PrNH) 2 C=O} 2 [NaC 5 H 3 {C(NH i Pr)(=N i Pr)} 2-1,2] 2 (2), contains the new 6-aminofulvene-2-aldiminate ligand in the N,N-chelating coordination mode with the cyclopentadiene ring being uncoordinated. In this case, dimerization occurs through the presence of two bridging neutral N,N-diisopropylurea ligands. Both compounds have been structurally characterized by single-crystal X-ray diffraction.

Synthetic Routes towards Multifunctional Cyclopentadienes

“…[30,31] An alternative path startingf rom sodium cyclopentadienide was pursued in work by the groups of Bildsteina nd Edelmann (Scheme 8). [32] These approaches allow,i np rinciple, for the introduction of av ariety of different amines and anilines. However,n ot many examples have been investigated to date.…”