Hypercoordination by multiple dangling benzylmethoxy ligands in highly crowded triaryltin bromide [(2-MeOCH2C6H4)3]SnBr and diaryltin mixed halides [(2-MeOCH2C6H4)2]SnBrCl.

Abstract

The reaction between the Grignard reagent formed between Mg and 2-bromobenzylmethyl ether and SnCl4 produced four products: [2-(MeOCH2)C6H4]3SnBr (1), [2-(MeOCH2)C6H4]2SnX2 (2, X2 = Br2 (a) and BrCl (b)), [{2-(MeOCH2)C6H4}3Sn]2 (3), and [{2-(MeOCH2)C6H4}2SnBr]2O (4). In the case of 1, two of the three dangling arm O atoms coordinate to the central tin atom with O-Sn internuclear distances of 2.53 (O1) and 2.91 (O2) Å, the shorter interaction being trans to the Br atom, the other trans to a phenyl carbon atom. In the case of 2 the resulting hexacoordinate structure exhibits two very short O---Sn interactions of 2.42 and 2.50 Å, well below the sum of the VdW radii of O and Sn, 3.69 Å. The sterically crowded ditin compound 3 was obtained in trace amounts and the structure demonstrates no dangling O---Sn interactions. General changes in structure compared to other distannane systems are reflective of the great steric crowding. Distannoxane 4, has a Sn-O-Sn bond angle of 148.1(2)o which is larger compared to other distannoxane structures. The intermolecular interactions between Sn---O 2.470(3) and 2.521(3)Å and 2.665(3) and 2.629(3)Å for Sn1 and Sn2 respectively are responsible for a distorted octahedral geometry around the two tin atoms.