Self-assembly of High-nuclearity Metal Clusters: Programmed Expansion of a Metallasiloxane Cage to an Octacopper(II) Cluster

The novel octanuclear Cu(II) cluster [Cu6{(PhSiO2)6}2{NCCu(Me6tren)}2(MeOH)4]2+ (1) was isolated as a perchlorate salt by reacting the hexacopper(II) metallasiloxane cage [Cu6{(PhSiO2)6}2(nBuOH)x] (x = 4, 6) with [Cu(Me6tren)CN]ClO4 in a MeOH/CHCl3 mixt. (Me6tren = tris(2-(dimethylamino)ethyl)amine). Crystal data for 1(ClO4)2·MeOH: monoclinic, space group P21/n, a = 16.8490(3), b = 22.2966(4), c = 17.2508(3) Å, β = 94.7658(5)°, Z = 2. The structure comprises a highly distorted hexagonal Cu6 array linked to two [Cu(Me6tren)] units via cyanide bridges. Magnetic measurements reveal that the addn. of the Cu cyanide complexes dramatically affects the magnetism of the Cu6 unit, whose ground spin state changes from S = 3 to S = 0.