NONCLASSICAL CARBONYL-COMPLEXES OF ZIRCONIUM - THE SYNTHESES, CHARACTERIZATION, AND REACTIVITIES OF (ETA(5)-C(5)ME(5))(2)ZR(ETA(2)-E(2))(CO) (E=S, SE, TE)

The non-classical zirconium carbonyl complexes Cp2(*)Zr(eta(2)-E(2))(CO) (E = S, Se, Te) have been prepared by the reactions of Cp(2)*Zr(CO)(2) with the elemental chalcogens (ca. two equivalents) at ca. 80 degrees C. Cp(2)*Zr(eta(2)-E(2))(CO) are characterized by v(CO) stretching frequencies of 2057 cm(-1) (E = S), 2037 cm(-1) (E = Se) and 2006 cm(-1) (E = Te), and the ditellurido derivative Cp(2)*Zr(eta(2)-Te-2)(CO) has been structurally characterized by X-ray diffraction. The dichalcogenido-carbonyl complexes Cp(2)*Zr(eta(2)-E(2))(CO) (E = S, Se, Te) react further with excess chalcogen to give the trichalcogenido complexes Cp(2)*Zr(eta(2)-E(3)), which have also been structurally characterized by X-ray diffraction. The formation of the tritellurido complex Cp(2)*Zr(eta(2)-Te-3) is reversible, and addition of CO (1 atm) regenerates Cp(2)*Zr(eta(2)-Te-2)(CO). In the presence of pyridine, the dichalcogenido derivatives Cp(2)TZr(eta(2)-E(2))(CO) react with Cp(2)*Zr(CO)(2) to give the terminal chalcogenido complexes Cp(2)*Zr(E)(NC5H5). Cp(2)*Zr(eta(2)-Te-2)(CO) exists in both triclinic and tetragonal modifications. Interestingly, the derived Zr-CO bond lengths for the two structures were significantly different, while the C-O bond lengths for each structure were similar. The origin of the discrepancy was determined to be crystallographic disorder in the tetragonal modification, and appropriate modeling allowed the derivation of a reasonable Zr-CO bond length for the tetragonal form.