π‐Complexes of p‐block elements: (η⁶‐Mesitylene)tin(II) chloride tetrachloroaluminate(III), a coordination polymer

Abstract (η 6 ‐1,3,5‐Trimethylbenzene)tin(II) chloride tetrachloroaluminate(III), (η 6 ‐1,3,5‐C 6 H 3 Me 3 )SnCl (AlCl 4 ), has been obtained from the reaction of anhydrous SnCl 2 and AlCl 3 in the molar ratio 1 : 2 in excess mesitylene as a solvent. The compound crystallizes in monoclinic needles, space group P2 1 /n, containing a coordination polymer with planar four‐membered rings Sn‐Cl‐Sn‐Cl as the fundamental structural units. Each tin(II) atom of these rings is η 6 ‐bonded to a mesitylene ring, with the metal approximately centered over the aromatic hydrocarbon at a distance of 2.71 Å. Each of the tin(II) atoms is further connected to two tetrachloroaluminate counter ions, one of these monodentate and one bidentate. Through this mono/bidentate contacts a one‐dimensional coordination polymer is generated with crystallographic centers of inversion in the middle of the Sn(Cl) 2 Sn and Sn(AlCl 4 ) 2 Sn rings. The structure is similar to that of the analogous benzene complex, but not identical owing to a different connectivity pattern. Also, the arene‐Sn(II) distance is much shorter in the mesitylene complex (2.71 Å) than in the benzene complex (2.90 Å), indicating that the trimethylbenzene molecule is a much better donor than benzene.