Chlorometallate-Pyridinium Boronic Acid Salts for Crystal Engineering: Synthesis of One-, Two-, and Three-Dimensional Hydrogen Bond Networks

A series of new crystal structures of salts containing 3- and 4-pyridineboronic acid (3- and 4-pba) with chlorometallate have been prepared: [4-pbaH][MnCl 2 ] ( 1 ), [4-pbaH][CdCl 2 ], ( 2 ), [4-pbaH] 2 [CuCl 4 ] ( 3 ), [4-pbaH] 2 [PdCl 4 ] ( 4 ), [3-pbaH] 2 [CdCl 4 ] ( 5 ), [3-pbaH][CuCl 3 (OH 2 )] ( 6 ), and [3-pbaH][PdCl 2 ] ( 7 ). In these salts five structural forms for the chlorometallate species are observed: mononuclear square planar [M = Pd ( 4 and 7 )], dimeric square-pyramidal [M = Cu ( 3 )], polymeric square-pyramidal [M = Cu ( 6 )], polymeric trans -edge-sharing octahedral [M = Mn ( 1 ), Cd ( 2 )], and polymeric cis -edge-sharing octahedral [M = Cd ( 5 )]. The cyclic R2,2(8) boronic acid dimer is formed in the salt of 1 – 5 . NH···Cl 2 M synthons A have been exploited in 1 – 4, 6, and 7 . Both NH···Cl 2 M (sythons A ) and B(OH) 2 ···Cl 2 M (sythons B ) interactions give rise to a synthon of form I in 6 . The uncommon folded conformation of the NH···Cl 2 M (synthons A ) are formed in 7 . The NH or OH donors and consequent branching of the NH···Cl hydrogen-bond network leads to one-, two-, and three-dimensional structures. These structures are further stabilized by CH···O and CH···Cl and π···π stacking interactions.