Hydrogen-bonded extended arrays of the [Re₆(μ₃-Se)₈]²⁺ core-containing clusters

Site-differentiated solvated clusters of the general formula [Re₆(μ₃-Se)₈(PEt₃) _n(MeCN)_6-n](SbF₆)₂ (n = 4, cis and trans; n = 5) undergo ligand substitution reaction with isonicotinamide to afford the corresponding amide derivatives, [Re₆(μ₃-Se)₈(PEt₃) _n(isonicotinamide)_6-n]²⁺ [1 (n = 5); 2 (n = 4, trans); 3 (n = 4, cis)]. Retention of stereochemistry in each case was confirmed by ¹H and ³¹P NMR. The solid-state structures of all three compounds were established crystallographically, which revealed self-complementary hydrogen-bonding interactions between adjacent cluster units. While complex 1 exists as hydrogen-bonded dimers in the solid state, compounds 2 and 3 form one-dimensional chains of clusters bridged by paired hydrogen bonds. It is the rigid stereochemistry of the cluster, combined with the classic crystal engineering motif of complementary N-H⋯O amide hydrogen bonding, that affords the predictable solid-state structures and dimensionality.