Non-classical carbonyl complexes of zirconium: The syntheses, characterization, and reactivities of ( η5-C 5Me 5) 2Zr( η2-E 2)(CO) (E  S, Se, Te)

Abstract

The non-classical zirconium carbonyl complexes Cp 2 ∗Zr (η 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°C. Cp 2 ∗Zr (η 2- E 2)( CO) are characterized by ν 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 (η 2- Te 2)( CO) has been structurally characterized by X-ray diffraction. The dichalcogenido-carbonyl complexes Cp 2 ∗Zr (η 2- E 2)( CO) (E  S, Se, Te) react further with excess chalcogen to give the trichalcogenido complexes Cp 2 ∗Zr (η 2- E 2) , which have also been structurally characterized by X-ray diffraction. The formation of the tritellurido complex Cp 2 ∗Zr (η 2- Te 3) is reversible, and addition of CO (1 atm) regenerates Cp 2 ∗Zr (η 2- Te)( CO) . In the presence of pyridine, the dichalcogenido derivatives Cp 2 ∗Zr(η 2- E 2)( CO) react with Cp 2 ∗Zr(CO) 2 to give the terminal chalcogenido complexes Cp 2 ∗Zr ( E)( NC 5H 5 ). Cp 2 ∗Zr (η 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 modelling allowed the derivation of a reasonable ZrCO bond length for the tetragonal form.