Anionic germanium polycobalt carbonyl clusters. Part 2. Preparation and structure of [NEt4][Ge{Co5(CO)16}], a cluster which contains five-co-ordinate germanium
Abstract
Addition of [Co(CO)4]– to [Ge{Co4(CO)n}](n= 16, 14, or 13) under mild conditions gives good yields of [Ge{Co5(CO)16}]–. This forms crystals with NEt4+ which are orthorhombic, space group Pn21a with a= 12.014(1), b= 36.938(4), c= 15.249(2), and Z= 8. The crystal structure was solved by direct methods and refined, with some difficulty due to pseudo-symmetry, to R= 0.088, R′= 0.081, for 1 590 unique reflections with F2 > 2σ(F2). The anion has a GeCo5 metal skeleton consisting of a GeCo2 triangle and a GeCo3 tetrahedron sharing a common apex at Ge. The five Ge–Co bond lengths vary from 2.33 to 2.51 Å. Three of the CO ligands on the GeCo3 unit bridge the three Co–Co bonds, with two terminal CO groups on each Co atom. On the GeCo2 moiety there are six terminal and one bridging carbonyls.