Preparations of cobalt-containing phosphines and reactions toward dicobalt octacarbonyl

Treatments of bis(diphenylphosphino)methylene (dppm) bridged dicobalt complex, Co2(CO)6(μ-Ph2PCH2PPh2), with alkynes, Ph2PCCR (2: R=CMe3; 3: R=SiMe3), at 60 °C in THF for 6 h gave alkyne-bridged complexes [(μ-Ph2PCH2PPh2)Co2(CO)4][(μ-Ph2PCCR)] (4: R=CMe3; 5: R=SiMe3). Further reactions of 4 and 5 with Co2(CO)8 at 80 °C in toluene for 3 h resulted in the formations of unexpected tetra-cobalt clusters, [(μ-Ph2PCH2PPh2)(μ-PPh2)Co4(CO)7(μ4,μ2-CCR)] (6: R=CMe3; 7: R=SiMe3). All these compounds were characterized by spectroscopic means; 5, 6 and 7 were studied by X-ray diffraction methods as well. The structure of 6 (or 7) can be looked upon as a tetra-cobalt arachno cluster being coordinated with phosphine ligands and linked by organic moiety.