Synthesis of complexes of dimethyltin(IV) with mono- and di-deprotonated pyridoxine (PN) in media with various anions. Crystal structures of [SnMe2(PN – H)]NO3·2H2O, [SnMe2(H2O)(PN – H)]Cl·H2O and [SnMe2(H2O)(PN – 2H)]·0.5H2O