Molecular {(SnO)_6} Trapped by Two {R_2Si_2O_3} Fragments: X-ray Single-Crystal Structure of [(SnO)_6(R_2Si_2O_3)_2]

摘要

We have a long-standing interest in the design and synthesis of molecular assemblies that contain the {Si-O-M} motif. This interest is motivated, in part, by the possibility of these soluble metallasiloxanes functioning as structural models for the more-complex naturally occurring metallasilicates or synthetic metal-modified zeolites. Another reason for our interest stems from the opportunity provided by molecular metallasiloxane structural frameworks for incorporating basic structural motifs of inorganic oxides as part of the larger cage or ring structures. Such systems can be viewed as organic-soluble solids that contain the inorganic oxide core enveloped by a sheath of lipophilic organic exterior. Although tin(II) alkoxide cage structures have been known for some time, there is a relative paucity of the corresponding tin(II) siloxane cages. In contrast molecular stannasiloxanes that contain tin(IV) have been widely studied. Herein, we describe the synthesis and structural characterization of [(SnO)_6(R_2Si_2O_3)_2] [R=(2,6-iPr_2C_6H_3)N(SiMe_3)] 1. This compound represents the first example of a hexatin(II) cage that contains siloxane ligands. Interestingly compound 1 contains a central embedded tin oxide, in the form of a molecular {(SnO)_6} motif between two {R_2Si_2O_3} fragments. To the best of our knowledge, there has been no previous report on the isolation and structural characterization of any molecular tin(II) oxide.