Hydrogen-Bonded Extended Arrays of the [Re6((mu)3-Se)8]2+ Core-Containing Clusters

Site-differentiated solvated clusters of the general formula [Re6(3-Se)8(PEt3)n(MeCN)6-n](SbF6)2 (n = 4, cis and transʹ, n = 5) undergo ligand substitution reaction with isonicotinamide to afford the corresponding amide derivatives, [Re6(3-Se)8(PEt3)n(isonicotinamide)6-n] [1 (n = 5); 2 (n = 4, trans)ʹ, 3 (n = 4, cis)]. Retention of stereochemistry in each case was confirmed by H and P 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-0 amide hydrogen bonding, that affords the predictable solid-state structures and dimensionality.