New stibines containing acetal and formyl group: Platinum complex and unexpected oxastibol derivative

A new tertiary stibine ligand (1) containing acetal group at the ortho-position has been synthesized. This new stibine was then complexed with to obtain trans-PtCl₂L₂ (2) where stibine acts as a monodentate ligand. The acetal was hydrolyzed in a slightly acidic medium and forms a very new stibine (3) containing formyl group at the ortho-position. When (3) was reduced with NaBH₄ an unusual oxastibol (4) derivative was obtained under the experimental conditions used.All the compounds were characterized by IR, mass, ¹H, ¹³C, COSY and HETCOR NMR spectroscopy. The molecular structures of (2), (3) and (4) were determined. Compound (3) crystallizes in two different polymorphs (3a) and (3b) and both the polymorphs show hypervalent antimony with three Sb?O interactions and the molecule exists in O-cis-exo configuration. Compound (4) shows intramolecular Sb?O interactions. To the best of our knowledge this is the first report on organoantimony compounds containing carbonyl groups though their phosphorus and bismuth analogues are well known. Compound (2) shows helicoidal chirality, which is a very new concept in antimony chemistry