Carbonylation of a Tetrameric Aryloxocopper(I) Cluster

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Abstract
Carbonylation of 2,6-diphenylphenoxocopper(I), tetrameric [(CuOC6H3Ph2)4] (1, Ph = C6H5), has been shown to result in a [{Cu(OC6H3Ph2)(CO)}2] dimer (2). The parent aryl oxide, [(CuOC6H3Ph2)4], which has been prepared from mesitylcopper(I) and 2,6-diphenylphenol, has an approximately planar Cu4O4 core, in which copper(I) is two-coordinated and Cu−O bonds range from 1.834(7) to 1.865(7) Å. Its carbonylation product 2 is a μ2-phenoxo-bridged dimer, containing three-coordinated copper(I), with longer Cu−O bonds, viz. 1.953(7)−1.995(7) Å. Cu−C bond lengths in [{Cu(OC6H3Ph2)(CO)}2] are 1.78(1) and 1.79(1) Å, respectively, with both carbonyl C−O distances equal to 1.12(1) Å, and Cu−C−O angles of 174(1) and 179(1)°, respectively. Carbonyl stretching frequencies in the infrared are 2099, 2103, and 2112 cm-1 for the solid and 2102 cm-1 in toluene solution, and the 13C NMR signal (toluene solution) is at 168 ppm. From comparison with other carbonyl complexes of copper(I), the Cu−C bond is judged to be predominantly of σ character, with minimal metal → ligand π* contribution. Both [(CuOC6H3Ph2)4] and [{Cu(OC6H3Ph2)(CO)}2] retain their aggregation states on dissolution in nonpolar solvents, as ascertained by cryoscopic molecular weight determinations of the compounds in benzene. Crystal data: 1, triclinic, space group P1̄ (No. 2), a = 12.738(9), b = 22.426(5), and c = 9.984(3) Å, α = 101.62(2), β = 91.02(4), and γ = 85.93(3)°, Z = 2, R = 0.052 (Rw = 0.058) for 721 parameters and 3843 reflections; 2, triclinic, space group P1̄ (No. 2), a = 10.67(3), b = 15.72(1), and c = 10.05(1) Å, α = 96.99(8), β = 104.66(16), and γ = 101.46(12)°, Z = 2, R = 0.049 (Rw = 0.054) for 397 parameters and 2152 reflections.