Pyridinium boronic acid salts in crystal synthesis

Abstract

A series of salts of pyridinium boronic acids: [HNC5H4B(OH)(2)- 4](2)[M(S2C2O2)(2)] center dot 2H(2)O (M = Cu 1, Ni 2, Pd 3, Pt 4), [HNC5H4B(OH)(2)- 4](2)[Pt(O2C2O2)(2)] ( 5); [HNC5H4B(OH)(2)- 3](2) [M(S2C2O2)(2)] (M = Cu 6, Ni 7, Pd 8, Pt 9) and [HNC5H4B(OH)(2)- 3](2)[Pt(O2C2O2)(2)] ( 10) have been prepared and characterized by X-ray diffraction methods. Salts 2, 3 and 4 are isostructural and isomorphous and contain hydrogen-bonded supermolecules of form [pyridinium](2)[M(S2C2O2)(2)] linked by BOH center dot center dot center dot OB and B(OH) - water hydrogen bonds into a three-dimensional network. Anhydrous salt 5 has a different structure in which the ions are linked by R(2,2)8 B(OH)(2) center dot center dot center dot carboxylate and pyridinium center dot center dot center dot carboxylate interactions to form a planar hydrogen-bonded ribbon. Salts 6, 7, 8 and 10 are all isostructural and isomorphous and contain hydrogen-bonded supermolecules of form [pyridinium](2)[M(S2C2O2)(2)] linked by B(OH)(2) center dot center dot center dot carboxylate synthons to form a stepped chain. These chains pack in layers superimposed so as to afford short metal center dot center dot center dot metal contacts of length 3.6 - 4 angstrom between layers. The structure of 5 is isomorphous with that of salts 6 - 8 and 10 but with a different pattern of NH hydrogen bonding as a result of the different isomer of pyridinium boronic acid present.