STRUCTURAL INVESTIGATIONS OF VAPOCHROMIC BEHAVIOR - X-RAY SINGLE-CRYSTAL AND POWDER DIFFRACTION STUDIES OF [PT(CN-ISO-C3H7)(4)][M(CN)(4)] FOR M = PT OR PD

We have synthesized [Pt(CN-iso-C3H7)(4)][M(CN)(4)] (M = Pt, Pd) and st udied their reversible hydration and sorption properties with UV-vis, FT-IR spectroscopy, and X-ray diffraction. Powder diffraction studies show that anhydrous [Pt(CN-iso-C3H7)(4)][Pt(CN)(4)] and [Pt(CN-iso-C3H 7)(4)][Pd(CN)(4)] crystallize in a tetragonal space group with nearly identical lattice constants. Gravimetric studies reveal that variable guest-host stoichiometries occur when solid [Pt(CN-iSO-C3H7)(4)] [Pt(C N)(4)] sorbs the guest at room temperature from the gas phase [water, 12.1(1)molecules per formula unit, chloroform 6.0(1), methanol 8.0(1), and trifluoroethanol 4.1(1)]; these sorption processes are reversible . The unit cell distances in the tetragonal ab-plane expand dramatical ly when the solvent guests are sorbed, but changes along the c-axis (t he M-M direction) are minimal. Crystallization of [Pt(CN-iso-C3B7)(4)] [Pt(CN)(4)] from water gives monoclinic crystals of a hexadecahydrate [Pt(CN-iso-C3H7)(4)][Pt(CN)(4)]. 16H(2)O. This salt consists of altern ating cation/anion chains along b with an average Pt-Pt distance of b/ 2 = 3.1521(1) Angstrom. The sixteen water molecules per formula weight interlace neighboring chains via H-bonding with each other and the CN - ions of the Pt(CN)(4)(2-) units. The shifts in the UV-vis and IR spe ctra that occur when solvent guests are sorbed by the double complex s alts are discussed in terms of the lattice expansions that are observe d. A mechanism for the lattice expansions that accompany the sorption of guest molecules is proposed.