Solid-state structure and solution behaviour of hypervalent organoantimony halides containing 2-(Me2NCH2)C6H4- moieties

Hypervalent antimony(III) halides of the type R2SbX [X = Cl (1), Br (2), I (3)] and RSbX2[X = Cl (4), Br (5), I (6)][R = 2-(Me2NCH2)C6H4] have been prepared. Their dynamic solution behavior was investigated by 1H and 13C NMR spectroscopy. The structures of compounds 2-6 were determined by single-crystal X-ray diffraction and the observed trends in the degree of intramolecular coordination of the N atom of the pending CH2NMe2 arm are discussed. Compounds 2 and 3 are monomeric and exhibit distorted square-pyramidal (C,N)2SbX cores. The molecular structure of the adduct R2SbI·HI (3·HI) indicates the strong coordination of one of the N atoms to antimony. The second pendant arm is twisted away from the metal center, its N atom being protonated and thus converted into an ammonium group. The molecules of 4-6 contain a pseudo-trigonal bipyramidal geometry around the antimony atom, with the N atom strongly coordinated trans to a halogen atom. Different degrees of association through asymmetric Sb-X...Sb bridges [overall distorted square-pyramidal (C,N)SbX3 cores] were found in the crystal of the dichloride 4(polymeric chains) and dibromide 5 and diiodide 6 (centrosymmetric dimers), respectively. In an attempt to obtain [R3SbI]I3 by addition of I2 to R3Sb in 2 : 1 molar ratio, deep red-brown crystals of the new ionic species [R3SbOH]+[I3]-(7) have been isolated. Crystals of 7 are built up from [R3SbOH]+ cations and linear non-symmetric [I3]- anions.