N,N'-Dialkyl-1,3-propanedialdiminate complexes of copper(I) and oxidation of β-dialdiminates by copper(II).

Three new copper(I) complexes derived from N,N'-dialkyl-β-dialdiminate anions (alkyl = iso-propyl or tert-butyl) are reported. Treatment of CuBr with Li[tBuN(CH)3NtBu] affords the tetrameric copper(I) compound Cu4[tBuN(CH)3NtBu]4. In this tetramer, the β-dialdiminate ligands adopt open-chain conformations that link the copper(I) centers into a boat-shaped 24-membered ring. Interestingly, the tetramer dissociates over several hours in solution into a dimer of stoichiometry Cu2[tBuN(CH)3NtBu]2. When copper(II) chloride is treated with Li[tBuN(CH)3NtBu], or copper(II) methoxide is treated with H[iPrN(CH)3NiPr], redox reactions take place in which the metal center is reduced to copper(I) and the β-dialdiminate anion or β-dialdimine is oxidized. Two copper(I) complexes containing oxidized β-dialdiminate groups have been isolated: in both complexes, the oxidized group has been dehydrogenated and oligomerized through C-C bond formation. All three compounds have been characterized by X-ray crystallography; selected NMR, IR, EA, and UV-Vis spectra are also reported.