CRYSTALLOGRAPHIC CONFIRMATION OF PROTONATION IN TRANS-DIOXOTETRAPYRIDINE-RHENIUM(1- CRYSTAL STUCTURES OF [REO(OH)(PY)(4)](CLO4)(2)CENTER-DOT-H2O AND [REO(OH)(PY)(4)](PF6)(2)CENTER-DOT-0.5H(2)O() )

The monoprotonation product of the trans-dioxotetrapyridinerhenium(1+) complex was isolated as the perchlorate and the hexafluorophosphate s alts and both were crystallographically characterized. The perchlorate salt crystallizes in the monoclinic space group C2/m, Z = 2, a = 15.3 21(2), b = 9.287(1), c = 9,325(1) Angstrom, beta = 91.19(1)degrees. Fu ll-matrix least-squares refinement of 2042 reflections gave R = 0.041. The rhenium atom in the [ReO(OH)(py)(4)](2+) cation crystallizes on a mirror plane perpendicular to the Re = O bond in a disordered mode an d yields only an average Re-O bond length of 1.765(5) Angstrom. The he xafluorophosphate salt of the hydroxooxotetrapyridinerhenium(2+) compl ex crystallizes in the tetragonal space group /4/m, Z = 4, a = b = 12. 943(1), c = 16.570(2) Angstrom. A full-matrix least-squares anisotropi c refinement of 1125 reflections gave R = 0.022. In this salt the Re = O and Re-OH bond lengths of 1.714(6) and 1.811(5) Angstrom are accura tely determined, confirming that the [ReO(OH)(py)(4)](2+) ion exists i n the solid state, and yielding the shortest Re-V-OH distance known to date. The crystallographic results are correlated with literature dat a for the infrared and acid-base behaviour of known trans-[ReO(2)L(4)] complexes.