SYNTHESES, PROPERTIES AND X-RAY CRYSTAL-STRUCTURES OF HEXANUCLEAR COBALT - CHALCOGEN CLUSTERS CO6S8(PPH3)6 AND CO6SE8(PPH3)6.THF

The reaction of Na2X(x) (X = S or Se) with CoBr2 and triphenylphosphine in DMF gave rise to the clusters Co6X8(PPh3)6 [X = S (I), X = Se (II)] in high yields. The molecular structures of I and II have been determined by single-crystal X-ray diffraction. Both structures were solved by direct methods and refined by full-matrix least-squares techniques to converge with R = 0.053 for I and 0.048 for II on the basis of 5488 and 8175 reflections with I > 3-sigma-(I), respectively. The two clusters are isostructural with the inner core consisting of a slightly distorted Co6 octahedron. The Co-Co distances fall in the ranges of 2.848-2.894 angstrom for I and 2.955-3.037 angstrom for II. Electrochemistry in dichloromethane shows the electron-transfer sequence for I: Co6S8(PPh3)6 reversible [Co6S8(PPh3)6]+ and for II: Co6Se8(PPh3)6 reversible [Co6Se8(PPh3)6]+ reversible [Co6Se8(PPh3)6]2+.