Structural chemistry of organically templated transition metal phosphite chlorides, [BH2][M(H2PO3)2Cl2] (B = diamine, M = Mn-Ni, Cd) as new analogs of "hydroselenite halides"

Following the previously reported (enH(2))[Co(H2PO3)(2)Cl-2] (enH(2) = ethylenediammonium cation), we successfully prepared its analogs with other divalent transition metal cations: Mn2+, Fe2+, Ni2+, and Cd2+. These compounds are isostructural to each other and the archetypic hydroselenites, (enH(2))[M(HSeO3)(2)X-2]. Despite evident similarities, some essential differences are observed between hydroselenites and hydrophosphites, both in chemistry and in structural details. Due to smaller size of H2PO3- relative to HSeO3-, only chloride phosphites could be prepared; the reducing capacity of H2PO3- permits preparation of Fe-II compound but not that of Cu-II. A single attempt to introduce piperazinediium cation instead of ethylenediammonium results in formation of (pipH(2))[Co(H2PO3)(2)Cl-2] with a structure different from (pipH(2))[Cd(HSeO3)(2)Cl-2]. Another serendipitous product is the 1-methylpiperazinediium derivative, (mpipH(2))(2)[Co(H2PO3)(2)I-3][H(H2PO3)(2)], which features a yet unique complex hydrogen-bonded network.