Antimony Tartrate Transition-Metal–Oxo Chiral Clusters

A chiral
precursor K2Sb2(l-tartrate)2 was used for the assembly of three homochiral heterometallic
antimony­(III)–tartrate transition-metal–oxo clusters:
Mn­(H2O)6­[Fe4Mn4Sb6(μ4-O)6(μ3-O)2(l-tartrate)6­(H2O)8]·10.5H2O (1), [V4Mn5Sb6(μ4-O)6(μ3-O)2(l-tartrate)6­(H2O)13]·9.5H2O (2),
and (H3O)­[Ni­(H2O)6]2­[NiCrSb12(μ3-O)8(μ4-O)3(l-tartrate)6]·6H2O (3). In 1 and 2, the antimony tartrate
dimer precursor decomposes and recombines to form Sb3(μ3-O)­(l-tartrate)3 chiral trimers, which
act as scaffolds to construct negative-charged [Fe4Mn4Sb6(μ4-O)6(μ3-O)2(l-tartrate)6]2– in 1 and neutral [V4Mn5Sb6(μ4-O)6(μ3-O)2(l-tartrate)6] in 2. The
scaffold is flexible and accommodates different types of transition-metal–oxo
clusters due to the different possible coordination modes of the l-tartrate ligand. In 3, a two-level chiral scaffold
Sb3(μ3-O)­(l-tartrate)3Sb3 is formed from the precursor. Two such scaffolds are
linked by three bridging oxygen atoms to form a cavity occupied by
one Cr3+ ion and one Ni2+ ion disordered over
two positions. Cr3+ and Ni2+ ions are located
in two face-shared MO6 octahedra at the center of a negatively
charged [NiCrSb12(μ3-O)8(μ4-O)3(l-tartrate)6]3– cluster.