Copper (I) guanidinate dimers were generated by a salt metathesis route and structurally characterized. The guanidinates differed from the known amidinate dimers because of a large torsion of the dimer ring. This had a direct effect on their thermal chemistry. The thermal reactivity was investigated by several methods, including a novel temperature-resolved, gas-phase method that was monitored by mass spectrometry. The copper guanidinates underwent carbodiimide deinsertion to produce copper metal at temperatures between 225 −and 250 °C in the gas phase and at 125 °C in solution. The amidinate investigated also showed copper deposition at 190 °C in the gas phase, and 135 °C in solution, but without carbodiimide deinsertion. The guanidinate compounds deposited crystalline copper at 225 °C in a simple chemical vapor deposition experiment.