Preparation and Characterization of Boron Chelates with Pyridoxine. The Crystal and Molecular Structures of [B(H 2 pdn)(Hpdn)]·H 2 O and [Ph 2 B(H 2 pdn)] (H 3 pdn = Pyridoxine)

The 1:2 complex of boric acid with pyridoxine ( 1 ) crystallizes from aqueous solution as monohydrate in the triclinic space group ${\rm P}{\bar 1}$ . The molecular structure of 1 corresponds to the expected bis‐chelate containing two non‐equivalent pyridoxinate ligands, one of them being dianionic and the other one monanionic, betain‐like with a protonated pyridine nitrogen atom. In the crystal structure hydrogen bonding, involving the water molecule, provides a supramolecular arrangement in form of sheets parallel to [011]. The 1 H and 13 C NMR spectra of 1 reveal a fast proton exchange between the two ligands in aqueous solution. Two new boron‐pyridoxine complexes [Ph 2 B(H 2 pdn)] ( 2 ) and [B(C 2 O 4 )(H 2 pdn)] ( 3 ) (H 3 pdn = pyridoxine) were prepared and characterized. In The crystal structure of 2 (monoclinic, P2 1 /c) the molecules are linked to chains by N‐H···O hydrogen bonds along the b axis.