Tin(II) bromide
Tin(II) bromide is a chemical compound of tin and bromine with a chemical formula of SnBr. Tin is in the +2 oxidation state. The stability of tin compounds in this oxidation state is attributed to the inert pair effect. Structure and bonding. In the gas phase SnBr is non-linear with a bent configuration similar to SnCl in the gas phase. The Br-Sn-Br angle is 95° and the Sn-Br bond length is 255pm. There is evidence of dimerisation in the gaseous phase. The solid state structure is related to that of SnCl and PbCl  and the tin atoms have five near bromine atom neighbours in an approximately trigonal bipyramidal configuration. Two polymorphs exist: a room-temperature orthorhombic polymorph, and a high-temperature hexagonal polymorph. Both contain (SnBr) chains but the packing arrangement differs. Preparation. Tin(II) bromide can be prepared by the reaction of metallic tin and HBr distilling off the HO/HBr and cooling: However, the reaction will produce tin (IV) bromide in the presence of oxygen. Reactions. SnBr is soluble in donor solvents such as acetone, pyridine and dimethylsulfoxide to give pyramidal adducts. A number of hydrates are known, 2SnBr·HO, 3SnBr·HO & 6SnBr·5HO which  in the solid phase have tin coordinated by a distorted trigonal prism of 6 bromine atoms with Br or HO capping 1 or 2 faces. When dissolved in HBr the pyramidal SnBr ion is formed. Like SnCl it is a reducing agent. With a variety of alkyl bromides oxidative addition can occur to yield the alkyltin tribromide e.g. Tin(II) bromide can act as a Lewis acid forming adducts with donor molecules e.g. trimethylamine where it forms NMe·SnBr and 2NMe·SnBr It can also act as both donor and acceptor in, for example, the complex FB·SnBr·NMe where it is a donor to  boron trifluoride and an acceptor to trimethylamine.