Modular construction of 3D coordination frameworks incorporating SiF62- links: Accessing the significance of [M( pyrazole)4{SiF6}] synthon

Rational combination of Cd2+ cations, bitopic pyrazole ligands, bridging SiF62- and terminal NCS- anions provide generation of 3D frameworks and precise control over connectedness of the net nodes: two-fold interpenetrated 4-connected NbO-like net (nbo) in [Cd(Me(4)bpz)(2){NCS}(2)]center dot 2/3CH(2)Cl(2) (1), uninodal 5-connected noz framework in [Cd-2 (Me(4)bpz)(4){SiF6}{NCS}(2)]center dot 6CHCl(3) (2), novel 5-connected binodal topology (with a point symbol of {4(2).5(5).6(2).7} {4(2).5(6).6(2)}) in [Cd-2(Me(4)bpz)(4){SiF6}{NCS}(2)]center dot 2CH(2)Cl(2) (3) and 6-connected alpha-Po cubic nets (pcu) in [Cd(Me(4)bpz) 2{SiF6}]center dot 6H(2)O (4) and [Cd(Me(4)bpz)(2){SiF6}]center dot 1.5CH(2)Cl(2) (5) (Me(4)bpz = 3,3', 5,5'-tetramethyl-4,4'-bipyrazole). Hexafluorosilicate anions act as bridges between Cd ions yielding further linkage of 4-connected [Cd(Me(4)bpz)(2)] subtopologies. Characteristic and specific interaction between SiF62- and the metal-organic portion is conditioned by a synergy of coordination and multiple strong NH...F bonds, which suggests perfect compatibility of the bipyrazole and SiF62- linkers for the construction of 3D structures, either by pillaring of 2D layers or cross-linking of 3D frameworks. Two observed motifs, 1D [M(pyrazole) 4{m-SiF6}](n) (in 4 and 5) and discrete [{M{NCS}(pyrazole)(4)}(2){mu-SiF6}] (in 2 and 3) are discussed as special supramolecular synthons for the framework solids. An improved largescale and cost-effective procedure for the synthesis of the organic ligand Me(4)bpz is also described.