Tetraorganodistannoxanes

R2Sn(rV)] derivatives of N-Bz-Gly-Gly and N-Bz-Gly-Gly-Gly were found to involve both dicarboxylate binding to yield hexacoordinated Sn centers, and dimeric tetraorganodistannoxanes in which the carboxylates bind... 

One-dimensional polymeric tetraorganodistannoxanes based on a typical ladder arrangement L4R8Sn402 (L = ligand, e.g. halogen, carboxylate R = alkyl, aryl) were... 

The dicarboxylates of the tetraorganodistannoxanes R4Sn20(02CR )2 and of the tetraorganodistannanes R4Sn2(02CR )2 have special structures, and these are discussed in Sections 12.2 and 18.2.2, respectively. 

The cover picture of a double-ladder tetraorganodistannoxane and its solid state 119Sn NMR spectrum was kindly provided by Jens Beckmann and Dainis Daktemieks of Deakin University. 

Tetraorganodistannoxanes Simple Chemistry From a Personal Perspective 201... 

Tetraorganodistannoxanes, in all their variations, are usually crystalline, sharp-melting solids that are, depending on the substituent pattern at the tin atoms, sparingly to well soluble in common organic solvents. 

The chemistry of tetraorganodistannoxanes is as old as organotin chemistry itself, with the first reports made by Lowig and Cahours. However, it took more than hundred years until the true nature of this class of compounds was unravelled. 

The molecular structures of tetraorganodistannoxanes in the solid state are characterized by (i) the ladder-type motif formally realized by dimerization via 0->-Sn donor-acceptor interactions and (ii) the almost planar Sn4X402 layer (Scheme 2.10.1). 

In context with the rather simple synthetic procedures for making tetraorganodistannoxanes (Scheme 2.10.1), their catalytic activity in a variety of organic reactions, and their structural peculiarities, this class of organotin compounds has become among the most extensively investigated. 

Until 1991, there had been no structurally characterized unsymmetrically substituted tetraorganodistannoxanes, although the compound Et2BrSnOSnBm-Pr2 had been mentioned in an early report. We decided to start our investigations with f-butyl-substituted tin compounds because I had experience with these concerning good crystallization properties and their simple NMR spectra. 

Scheme 2.10.2 Schematic representation of the tetraorganodistannoxanes 1, 2, 6, 7, 10, and 11 including selected bond distances (A)...

Scheme 2.10.3 Equilibrium between the tetraorganodistannoxanes 1 and 3, as studied by Sn NMR spectroscopy...

In contrast to compounds 1 and 2, in solution the fluoro-substituted tetraorganodistannoxane 6, as well as its non-symmetrically substituted analog [f-Bu(F)SnOSn(F)n-Bu2]2 (7), are kinetically inert on the H, and Sn NMR timescales, indicating superior bridging capacity of fluoride over chloride... 

Figure 2.10.1 Molecular structure of [(t-Bu2FSn)20]2 (6), a fluoro-substituted tetraorganodistannoxane...

Scheme 2.10.4 Schematic representation of the five possible isomers for the tetraorganodistannoxanes (PhR(CI)SnOSn(CI)RPh]2 (8, R=Me3SiCH2 9, R= Me2(CH2CH)SiCH2>...

The hydrolysis of the non-symmetrically substituted diorganotin dichloride (Me3SiCH2)PhSnCl2 gives rise to formation of the tetraorganodistannoxane [(RPh(Cl)SnOSn(Cl)PhR]2 (8, R=Me3SiCH2), which in solution is kinetically labile on the laboratory timescale, but inert on the Sn NMR timescale. Thus, in solution, all five possible isomers of 8 are detected (Scheme 2.10.4). 

Tetraorganodistannoxane 11 is in equilibrium with cycto-(f-Bu2SnO)3 (14) and the mixed diorganotin oxides cydo-R2Sn(OSnf-Bu2)20, (15, R = Me3SiCH2), and cycto-f-Bu2Sn(OSnR2)20 (16,... 

Figure 2.10.3 Molecular structure of the perhydroxy-substituted tetraorganodistannoxane [t-Bu2(OH) SnOSn(OH)(CH2SiMe3)h (11)...

Notably, the tetraorganodistannoxanes [f-Bu2(OH)SnOSnClR2]2 (31, R = cyclohexyl [35] 32, R = Me3SiCH2[30]) containing both strongly and weakly coordinating anions, such as hydroxide and chloride, respectively, are, at least on the Sn NMR timescale, kinetically inert and this is in line with the observations made by Hasha on related compounds. ... 

Scheme 2.10.8 Strategies to link tetraorganodistannoxanes to give supramolecular networks...

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