New coppertelluride clusters - Syntheses, crystal structures, and optical spectra

Reactions of copper(I) acetate with Te(SiMe3)(2) lead in the presence of te rtiary phophines PR3 (R = organic group) to the formation of new coppertell uride clusters: [Cu8Te4(PPh3)(7)] (1), [Cu16Te9(PPh3)(8)] (2), [Cu23Te13(PP h3)(10)] (3), [Cu44Te23(PPh3)(15)] (4), [Cu12Te6(PPh3)(8)] (5), [Cu26Te12(P Et2Ph)(12)] (6), [Cu16Te8((PPr2Ph)-Pr-n)(10)] (7), [Cu44Te23((PPr2Ph)-Pr-n) (15)] (8), [Cu24Te12((PPr3)-Pr-i)(12)] (9). Simple electron counting on the basis of Cu1+ and Te2- suggests that the smaller and medium size clusters 1, 5, 7, and 9 are electron precise compounds and that on the other hand so me of the medium size and larger ones 2, 3, 4, and 8 must contain mixtures of Cu1+/Cu2+ ions or 6 Cu1+ ions and Cu-0 atoms. UV-VIS spectra in the soli d state strongly confirms this suggestion by showing broad intervalence ban ds in the region of higher wavelengths for the cluster compounds formally b eing not electron precise. Apparently then is also an interesting dependenc e of these intervalence bands on the Bite of the cluster molecules.