Stabilizing the [RSn(μ2‑O)SnR] Motif through Intramolecular N→Sn Coordination. Synthesis and Characterization of [(RSn)2(μ2‑O)(μ2‑FcCOO)2(η-FcCOO)2]·THF and {(RSn)2(μ2‑O)[(t-BuO)2PO2]2Cl2}·THF·2H2O (R = 2‑(Phenylazo)phenyl)

The reactions of RSnCl3 (1; R = 2-(phenylazo)­phenyl) with FcCOOH or di-tert-butyl phosphate in refluxing THF afforded the monoorganodistannoxanes [(RSn)2(μ2-O)­(μ2-FcCOO)2(η-FcCOO)2]·THF (2) and {(RSn)2(μ2-O)­[(t-BuO)2PO2]2Cl2}·THF·2H2O (3). The molecular structure of 2 contains seven-coordinate tin centers in a distorted-pentagonal-bipyramidal geometry, while 3 contains six-coordinate tin centers in a distorted-octahedral geometry. In the dinuclear compounds 2 and 3 the two tin centers are bridged by a μ2-O unit, affording a rare Sn–O–Sn motif among monoorganostannoxanes. In addition, each tin is also intramolecularly coordinated to the nitrogen atom of the 2-phenylazophenyl substituent (N→Sn). Further, in 2, the two tin centers are bridged by two isobidentate ferrocenecarboxylate ligands; each tin center also is bound to a chelating ferrocenecarboxylate ligand. On the other hand, in 3, while the two tin centers are bridged by two isobidentate di-tert-butyl phosphate ligands, each tin center also has a terminal chloride ligand.