Copper(I) alkoxides: preparation and structural characterisation of triphenylmethoxocopper(I) and of an octanuclear form of t-butoxocopper(I)

Two copper(I) alkoxides, the novel compound triphenylmethoxocopper(I) and an octanuclear form of t-butoxocopper(I), have been prepared from mesitylcopper(I) and the relevant alcohol. [Cu4(OCPh3)4]·2C6H5CH3 (1) and [Cu8(OtBu)8] (2) have been characterised by means of crystal structure determination. Compound 1 contains two crystallographically independent triphenylmethoxocopper(I) molecules, each with a planar Cu4 core. The Cu4O4 unit is butterfly-shaped with the oxygen ligands situated alternately approximately 0.4 Å above and below the plane through the copper atoms, and the triphenylmethyl groups spread out over both sides of the Cu4O4 core. The copper(I) centres are two-coordinated with distances of 1.83(1)–1.86(1) Å and OCuO angles of 169.4(5)°. [Cu8(OtBu)8] (2) can be described as being composed of two approximately planar Cu4O4 cores, each with the t-butyl groups bent away in the same direction from the Cu4O4 plane. These units are related to one another by a centre of symmetry and with weak CuO interactions of 2.493(5) and 2.536(5) Å, involving four of the eight coppers, thus yielding an octanuclear Cu8O8 core. These four copper(I) centres thus attain T-shaped three-coordination by oxygen, whereas the remaining four are approximately linearly coordinated. The short CuO bond lengths in 2 range from 1.844(5) to 1.888(5) Å.