The synthesis, characterization, and thermal decomposition behavior of dicopper(I) oxalato complexes L
4Cu
2(C
2O
4) (L = CN
tBu (
2a), CNCMe
2CH
2tBu (
2b), CNC
6H
3Me
2-2,6 (
2c)) is reported.
2c can be prepared in a straightforward manner by the reaction of stoichiometric amounts of Cu
2O and oxalic acid with four equivalents of CNC
6H
3Me
2-2,6, while those complexes with aliphatic isocyanides are better prepared from a copper(I) oxalato complex with alkine capping ligands (Me
3SiC
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CSiMe
3)
2Cu
2(C
2O
4) (
1) via ligand exchange. Crystallographic and spectroscopic evidence for
2a–
c confirms the anticipated dinuclear structure with the oxalate in a μ-1,2,3,4 bridging mode and an essentially σ-character of the terminal isocyanides. In solid form the complexes are stable at room temperature and can be handled in air for some time. Their decomposition was studied by thermal gravimetric analysis coupled with mass spectrometry, and the degradation pathway was shown to depend on the type of isocyanide capping ligand. Decomposition of
2a,
b takes place between 150 and 200 °C to give CuCN in a clean process that involves isobutene elimination from the terminal ligands, with elimination of (CN)
2 and conversion to elemental copper at higher temperatures. Heating of
2c leads to CuO (and then to Cu
2O) via release of the intact isocyanide, CO
2, and CO in a well-behaved thermal process around 200–280 °C.