Hydrothermal syntheses, crystal structures and physicochemical properties of 2-D and 3-D inorganic coordination cobalt(ii)-sulfite polymersElectronic supplementary information (ESI) available: IR and UV-vis spectra, and thermogravimetric curves. CCDC reference numbers 750027-750029. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/b920710d

The hydrothermal reaction of [Co III (NH 3 ) 6 ]Cl 3 with Na 2 SO 3 yields, depending on the concentration of Na 2 SO 3 , compounds {Na[Co II 2 (SO 3 ) 2 (μ 3 -OH)(H 2 O)]} ∞ ( 1 ) and {Na 4 [Co II 2 (SO 3 ) 4 ]} ∞ ( 2 ). When (NH 4 ) 2 SO 3 ·H 2 O was substituted for Na 2 SO 3 , the trinuclear mixed valence cobalt( ii / iii ) complex (NH 4 ) 4 {Co II [Co III (SO 3 ) 3 (NH 3 ) 3 ] 2 }·2H 2 O ( 3 ·2H 2 O) was isolated. The cobalt-sulfites 1-3 ·2H 2 O were structurally characterized. In 1 , the 1-D chains along the a -axis of the subunit [Co II (2)Co II (3)(OH) 2 (SO 3 ) 2 ] are cross-linked with Co II (1) atoms via Co-O sulfite and Co-O hydroxide bonds in 2-D sheets, that are further stacked through interlayer hydrogen bonds. In 2 , the [Co II 2 (SO 3 ) 2 ] ∞ chains along the b -axis are cross-linked with tetrahedral cobalts via Co II -O sulfite bonds in 2-D sheets parallel to the ab -plane and the sheets are further bound to sodium atoms via Na + -O sulfite bonds to form a 3-D structure. The 3-D inorganic coordination polymer, 2 , crystallizes in the non-centrosymmetric space group P 2 1 2 1 2 1 . In addition, in compound 2 octahedral and tetrahedral cobalt atoms coexist, which is rather unusual for cobalt clusters. Compound 3 ·2H 2 O is a 0-D mixed-valence {[(NH 3 ) 3 Co III (μ-SO 3 ) 3 ]Co II [(μ-SO 3 ) 3 Co III (NH 3 ) 3 ]} 4− trinuclear cluster and can be considered as an octahedral {Co II O 6 } complex ligated to two tridentate [(NH 3 ) 3 Co III (SO 3 ) 3 ] 3− ligands. The trinuclear clusters are stacked through an extended network of hydrogen bonding into a 3-D structure. Variable temperature magnetic susceptibility studies for 1-3 ·2H 2 O revealed that 1 and 2 are 2-D magnetic systems with strong antiferromagnetic interaction between the Co II atoms leading to an S = 0 ground state for 1 , while in compound 2 there is an almost zero interaction between the cobalt( ii ) atoms leading to a non-zero ground state. The trinuclear compound 3 ·2H 2 O has two diamagnetic Co III atoms and a high-spin Co II atom with D = 84(1) cm −1 , E = 6(1) cm −1 and g = 2.56(1). The IR, the solid-state UV-vis spectra and the thermogravimetric analyses of compounds 1-3 ·2H 2 O are also reported. The strategy of hydrothermal reaction of [Co III (NH 3 ) 6 ]Cl 3 with Na 2 SO 3 led to the synthesis of the cobalt( II )-sulfite 2-D and 3-D inorganic coordination polymers {Na[Co II 2 (SO 3 ) 2 (μ 3 -OH)(H 2 O)]} ∞ ( 1 ) and {Na 4 [Co II 2 (SO 3 ) 4 ]} ∞ ( 2 ), respectively. The c