Reaction of methanol with diphenylantimony(V) trihalides: crystal structure of [SbPh2Br2(OMe)·MeOH]2

Abstract

A re-examination of the reaction between diphenylantimony trichloride and methanol showed that the initial product is a methanol adduct of the monomethoxide, SbPh₂Cl₂(OMe), rather than the oxide (SbPh₂Cl₂)₂O, which is a hydrolysis product formed during recrystallisation. The corresponding tribromide, and the mixed halides, SbPh₂Br_3–nCl_n where n= 1 or 2, react similarly with methanol, losing a bromine atom to give solvated monomethoxy products. X-Ray diffraction analysis revealed that SbPh₂Br₂(OMe) crystallises as a centrosymmetric dimer, incorporating two molecules of methanol, which are attached via strong hydrogen bonds to the oxygen atoms of the methoxy groups. Co-ordination of the methanol oxygen to a symmetry-related antimony atom completes the distorted-octahedral co-ordination about antimony and forms a central eight-atom ring system in the chair conformation. Two unusual features are the similarity of the two Sb–O distances [2.101(4) and 2.121(4)Å], even though the former is formally a normal σ bond and the latter a donor linkage, and the presence of a weak π-arene ⋯ H–C hydrogen bond, which probably accounts for the orthogonality of the phenyl groups at antimony.