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

• Main Authors: Nicole Harmgarth, Phil Liebing, Liane Hilfert, Sabine Busse, Frank T. Edelmann
• Format: Article
• Language: English
• Published: MDPI AG 2018-05-01
• Series: Inorganics
• Subjects: Sodium; amidinate ligand; cyclopentadienyl; aminofulvene-aldiminate; crystal structure
• Online Access: http://www.mdpi.com/2304-6740/6/2/47

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 [NaC5H3{C(NHiPr)(=NiPr)}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 η5-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-(iPrNH)2C=O}2[NaC5H3{C(NHiPr)(=NiPr)}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.