Fivefold Deprotonated D ‐Mannose as Ligand in Homoleptic Dinuclear Metalates of Trivalent Iron, Vanadium, Chromium, Aluminum, and Gallium

Bridging by carbohydrate ligands instead of hydroxo or oxo ligands causes the formation of small complexes instead of networks for the trivalent atoms in the complexes 1 (M = Fe, V, Cr, Al, Ga; n ≈ 13). At slightly alkaline pH values all five acidic protons of the furanose form of D-mannose are split off: this pentaanion can then act as a pentadentate ligand. The crystal structure of the anion in complex 1, M = Fe, is displayed on the right.