Organic-Inorganic High-Valence Sn 18 -oxo Clusters: Direct Utilization of an Inorganic Sn(IV) Source to Improve the Nuclearity and Electrocatalytic CO 2 Reduction Properties.

The high-valence tin-oxo clusters are of great significance because of their structural diversity and potential applications in many fields, e.g., catalysis, extreme ultraviolet (EUV) lithography, and so on. The synthesis of high-nuclearity tin-oxo clusters remains a great challenge currently, since the key inorganic Sn x O y core with Sn 4+ ions could not be obtained only by the in situ Sn-C bond cleavage in organic tin sources. In this context, we synthesize three organic-inorganic hybrid Sn 18 -oxo clusters, [(BuSn) 12 Sn 6 (μ 3 -O) 20 (ba) 12 (PhPO 3 ) 4 ] (Bu = butyl, Hba = benzoic acid), [(BuSn) 12 Sn 6 (μ 3 -O) 20 (pmba) 12 (PhPO 3 ) 4 ]·2CH 3 CN·2H 2 O (Hpmba = p -toluic acid), and [(BuSn) 12 Sn 6 (μ 3 -O) 20 (ptba) 12 (PhPO 3 ) 4 ]·2CH 3 CN·2 i PrOH·2H 2 O (Hptba = p -tert-butyl benzoic acid), as well as one Sn 6 -oxo cluster [(BuSn) 6 (μ 3 -O) 2 (μ 2 -OH) 4 (pnba) 6 (PhPO 3 ) 2 ] (Sn 6 ) (Hpnba = p -nitrobenzoic acid) by combining an inorganic precursor (SnCl 4 ) with an organic one (butyltin hydroxide oxide). It is shown that an inorganic dicyclo-chain-like Sn 6 O 8 core encapsulated in a U-shaped dodecanuclear butyltin-oxo ring plays an important role in the construction of Sn 18 -oxo clusters and that the use of a ligand with an electron-withdrawing group reduces the nuclearity of clusters to Sn 6 . Moreover, electrocatalytic CO 2 reduction studies confirm that the electrocatalytic activities of the Sn 18 clusters are superior to those of the Sn 6 cluster, probably due to the hybrid organotin-inorganotin structures. Our work not only opens a new way for constructing high-nuclearity tin-oxo clusters but also is helpful in deeply revealing the structure-properties relationship of tin-oxo clusters.