Assembling Homometallic Sb6 and Heterometallic Ti4Sb2 Oxo Clusters.

Isolation and structural characterization of novel organoantimony(V)-based oxo clusters are reported. (RSb)4(OH)4(t-BuPO3)6 and (RSb)2(O)(t-BuPO3H)6 independently in the presence of pyridine under solvothermal conditions afford the hexanuclear organoantimonate clusters [(RSb)6(mu3-O)2(mu2-O)6(t-BuPO3)4], where R = p-i-PrC6H4 (1), p-ClC6H4 (2). Further, reaction of organostibonate phosphonate with Ti(O(i)Pr)4 in the presence of pyridine under solvothermal conditions afforded the mixed-metal titanium stibonate hexanuclear clusters [(RSb)2Ti4(mu3-O)2(mu2-O)2(t-BuPO3)4(mu-OCH3)4(OCH3)4], where R = p-i-PrC6H4 (3), p-ClC6H4 (4). Band gap measurements were performed on 1-4. They reveal a remarkable reduction in the band gap on moving from the heavier main-group-based oxo cages (1 and 2) to the titanium-incorporated oxo cages (3 and 4).