Methyltin trihalides

Diorganotin dihalides with in-built donor groups can form monomeric octahedral complexes (with two in-built donor centers) or trigonal bipyramidal complexes (with one in-built donor center), e g. (24) and (25). Methyltin trihalides are assumed, from spectroscopic evidence, to have polymeric structures. For monoorganotin halides with in-built donor centers, chelate structures with trigonal bipyramidal tin atoms are possible, e.g. (26) and (27). 

Few monoorganotin trihalides have been structurally characterized. Methyltin trichloride, MeSnCU is a tetrahedral molecule in the gas phase (electron diffraction) [202], but in the crystal both the trichloride [203] and the tribromide, MeSnBrs [204], are weakly associated by double bridges, 64. The bromide forms centrosym-metric dimers [MeSnBr3]2 (Sn-Br 2.454 A and Sn- - -Br 3.785 A). The iodide. 

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