Copper(I) chloride and bromide react with equimolar L=N,N-dimethylaminomethylferrocene in methylene chloride or nitrobenzene at room temperature under N2 to give soluble tetranuclear copper(I) complexes [LCuX]4 (VII). The room temperature electronic spectra of L and VII are very similar, indicating little, if any, electronic coupling of copper(I) with the ferrocene moiety. Products [CuX]4 completely reduce O2 to coordinated oxide in the tetranuclear oxocopper(II) products [LCuX]4O2 (VIII) that are converted by excess CO2 to tetranuclear dicarbonatocopper (II) complexes [LCuX]4(CO3)2 (IX). VII are oxidized by O2 to VIII in a second-order reaction whose rate-determining step is insertion of O2 through the halo core of VII. The properties of VIII are consistent with a (μ-O)2[LCuX]4 molecular core structure. The electrochemistry of L is not much affected by coordination to copper(I) or copper(II). Attempted crystallization of VIII and IX (XCl) gives (μ4-O)L4Cu4Cl6 (Xa), which crystallizes in the tetragonal space group P421c, with a=16.930(6), c=13.084(7) Å, V=3750 Å3 and Z=2. The crystallographic data from 1744 reflections at 233 K were refined to give R=0.047 and Rw=0.052. The core molecular structure of Xa consists of a central oxo group that is tetrahedrally coordinated to four copper(II) centers. Each copper(II) carries a monodentate ligand L and is bridged to three other copper(II) centers by chlorine ligands. This core structure is very similar to those of the N,N-diethylnicotinamide and pyridine analogues. Complexes VIII-X are not transmetalated at practical rates by Co(NS)2 and Ni(NS)2 (NS is monoanionic S- methyl isopropylidenecarbodithioate). Likely reasons are that steric effects interfere with reaction precursor formation and that VIII-X contain very strong copper-L bonds.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry