MAIN-GROUP-ORGANOTRANSITION-METAL CHEMISTRY - THE CYCLOPENTADIENYLCHROMIUM POLYIODIDES INCLUDING [(C5ME5)2CR2I3+]2[I162-]

The reaction of [Cp*Cr(CO)2]2 (Cp* = η5-C5Me5) and I2 affords a compound of the empirical formula Cp*CrI3 (2). Single-crystal X-ray diffraction shows 2 to be a polymer, {[Cp*CrI(η-I)]2*[Cp*Cr(I3)(η-I)]2}π [monoclinic P21\c; a = 15.658 (2), b = 8.504 (1), c = 23.242 (4) Å; β = 102.48 (1)°; V= 3021.7 (9) Å3; Z = 2; ρcak = 2.497 g cm-3; 3014observed reflections I > 2.58σ(I); R = 0.039, Rw = 0.041], 1H NMR studies show that in chlorinated solvents 2 dissociates into [Cp*CrI(η-I)]2 (1), the latter of which can be prepared by reduction of 2 with Zn/Hg. Treatment of 2 with high concentrations of I2 (I/Cr of >6) gives Cp*CrI55 (3), which is formulated as [Cp*2Cr2(η-I)3]2[I16] [monoclinic, P21/c; a = 14.744 (2), b = 22.864 (4), c = 23.267 (5) Å; β = 93.77 (2)°; V= 7827 (4) Å3, Z = 4; ρcak = 3.005 g cm-3; 6153 observed reflections I > 2.58 (I); R = 0.054, Rw = 0.063], The cation exhibits a short Cr-Cr distance of 3.00 (1) Å indicative of Cr(III)-Cr(III) bonding. This cation is imbedded within a three-dimensional polyiodide lattice based upon I162- subunits. The I162- cluster is comprised of an I2-linked pair of roughly planar (I2)3 subunits. © 1990, American Chemical Society. All rights reserved.