From an unusual organotin(IV) coordination compound to the first ionic organic-inorganic mixed-valent tin(IV)-tin(II) compound.

In the search for complexes of the monoorganotin(IV) triiodides, RSnI3, with Lewis bases, LB, a 1:3 complex was was obtained for the first time in the case of iso-propyl-tin(IV) triiodide, i PrSnI3, and LB = pyridine-N-oxide, PyNO. The compound, di-iodido-(isoprop-yl)tris-(pyridine N-oxide)tin(III) iodide, [Sn(C3H7)I2(C5H5NO)3]I, has an ionic structure and consists of a previously unknown [ i PrSn(pyNO)3]+ and an isolated I- ion. The novel cation exhibits a facial arrangement of the PyNO mol-ecules and a cis arrangement of the iodine atoms. In CDCl3, over the course of several weeks, this compound gives rise to a new, second compound, also of ionic structure, containing an tri-iodido-stannate(II) ion, [SnI3]-, and a solvent mol-ecule in addition to the already known cation, namely, di-iodido-(isoprop-yl)tris-(pyridine N-oxide)tin(IV) tri-iodido-stannate(II) deutero-chloro-form monosolvate, [Sn(C3H7)I2(C5H5NO)3][SnI3]·CDCl3. The anion exhibits a trigonal-pyramidal structure in order to achieve a stable electron octet at the divalent tin atom but is associated in the crystal via tetrel bonds into one-dimensional chains in which the tin atoms exhibit a 33-aaa coordination mode.