[Co{Ph2P(O)CH2P(O)Ph2}3][CoCl4] · 8CHCl3: Crystal structure and formation from [Co2(Ph2PCH2PPh2)(CO)6] in chloroform

When a solution of [Co2(Ph2PCH2PPh2)(CO)6] in chloroform or deuterochloroform is allowed to stand in air at room temperature, it deposits dark green crystals of [Co{Ph2P(O)CH2P(O)Ph2}3][CoCl4] · 8CHCl3. The same product is formed more quickly and in much higher yield (80% based on Co) if the reaction is carried out in the presence of 2 equiv. of [Ph2PCH2PPh2]; the CoII appears to catalyse the air-oxidation of [Ph2PCH2PPh2]. The salt was characterised by X-ray crystallography and shown to contain octahedral CoII cations and CoII tetrahedral anions having normal bond lengths and angles.