Synthesis and crystal and molecular structure of [(nC 4H 9) 4N] 2[MoO 2(C 5O 5) 2]; confirmation of exclusively η 2-coordination by a croconate ligand

Abstract

The reaction of [(nC 4H 9) 4N] 2[Mo 2O 7] with BaC 5O 5 in acetonitrile yields red crystals of [(n C 4H 9) 4N] 2[MoO 2(C 5O 5) 2]. The compound crystallizes in the monoclinic space group C2/ c with a=36.502(11), b=14.681(3), c=18.109(5) Å, β=93.84(1)°, V=9682.5(15) Å 3, D calc=1.22 g cm −3 for Z=8. Structure solution and refinement based on 3593 reflections with F o⩾6σ(F o) Mo Kα, λ= 0.71073 Å) converged at 0.0693. The structure of the anion consists of a mononuclear Mo(VI) center in ar distorted octahedral environment of the cis-oxo groups and the oxygen donors of two bidentate croconate ligands. The 1,2-chelating geometry of the croconate is unusual in that all previously structurally characterized examples of croconate coordination exhibit additional bonding to a second metal site via the oxygen donor in the 4 position.