Osmium−Germanium Clusters. Structures of [(OC)₄Os(GeMe₂)]₂, Os₂(GeMe₂)₃(CO)₆, Os₃(GeMe₂)₂(CO)₁₁, [(OC)₃Os(GeMe₂)]₃, and Os₄(GeMe₂)₄(CO)₁₂

Abstract

The complex [(OC)4Os(GeMe2)]2 (1) has been prepared from Na2[Os(CO)4] and Me2GeCl2 in THF. Photolysis of 1 in hexane affords the known [(OC)3Os(GeMe2)]3 (4) as the major product, along with the new clusters Os3(GeMe2)2(CO)11 (3) and Os4(GeMe2)4(CO)12 (5). Pyrolysis of 1, in hexane at 100 °C, gives the same compounds except that Os2(GeMe2)3(CO)6 (2) was also isolated, albeit in low yield. The structures of 1−5 have been determined; the configurations of 1, 2, and 4 are analogous to those previously found for group 8−group 14 congeners. The skeleton of 3 consists of two Os2Ge triangles that share a common osmium atom, that is, a "bow-tie" arrangement; the Os−Os lengths in 3 are crystallographically equivalent at 2.981(1) Å, and the Os−Ge lengths are 2.520(1) and 2.522(1) Å. The framework of 5 consists of a central triangulated (raftlike) Os3Ge3 unit (similar to that in 4) to one Os atom of which is bound an (OC)4Os(GeMe2) fragment so as to give an Os2Ge triangle that lies in the plane of the other metal atoms. The Os−Os bond length associated with this triangle is long (3.069(1) Å). The other Os−Os lengths in 4 range from 2.860(1) to 2.967(1) Å; the Os−Ge lengths are in the range 2.475(2)−2.584(2) Å. The 1H NMR spectrum of 5 in toluene-d8 is consistent with rotation of the (OC)4Os(GeMe2) unit with respect to the rest of the molecule at temperatures above 60 °C.