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

The novel octanuclear copper(II) cluster [Cu6{(PhSiO2)6}2{NCCu(Me6tren)}2(MeOH)4]2+ (1) has been 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 methanol/chloroform mixture (Me6tren = tris(2-(dimethylamino)ethyl) amine). Crystal data for 1(ClO4)2·MeOH: monoclinic, space group P21/n (no. 14), a = 16.8490(3) Å, b = 22.2966(4) Å, c = 17.2508(3) Å, ? = 94.7658(5)°, V = 6458.3(2) Å3, 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 addition of the copper cyanide complexes dramatically affects the magnetism of the Cu6 unit, whose ground spin state changes from S = 3 to S = 0.