Synthesis and structural characterization of novel palladium complexes chelated by bulky cobalt-containing phosphine ligands: unusual palladium-cobalt bond formation

The reaction of a bulky phosphine, [Co2(CO)5{(mu)-P,P-((mu)-PPh2C(identical)CPPh2)}][Co2(CO)4{(mu)-P-((mu)-PPh2C(identical) CPPh2)}]1 with P(OMe)3 gave a phosphite substituted tetracobalt-complex, [Co2(CO)4{P(OMe)3}{(mu)-P,P-((mu)-PPh2C(identical) CPPh2)}][Co2(CO)4{(mu)-P-((mu)-PPh2C(identical)CPPh2)}]5. Further reaction of 5 with (COD)PdCl2 yielded a 5 -coordinated palladium complex, [Co2(CO)4{P(OMe)3}}{(mu)-P,P-((mu)-PPh2C(identical)CPPh2)}][Co2(CO)3((mu)-CO){(mu)-P-((mu)-PPh2C(identical)CPPh2)}] PdCl27. Similar results were obtained for the reaction of 1 with (COD)PdCl2, which yielded [Co2(CO)5{(mu)-P,P-((mu)-PPh2C(identical) CPPh2)}][Co2(CO)3((mu)-CO){(mu)-P-((mu)-PPh2C(identical)CPPh2)}]PdCl26. Likewise, reaction of another bulky phosphine [((mu)Ph2PCH2PPh2)Co2(CO)4((mu)-PPh2C(identical)CP(=O)Ph2)]3 with (COD)PdCl2 yielded [{(mu)-P,P-PPh2CH2PPh2}Co2(CO)3((mu)-CO) {(mu)-PPh2C(identical)CP(=O)Ph2}]PdCl28. The X-ray structural studies of 6, 7 and 8 reveal that unusual palladium-cobalt bonds were formed. A Suzuki type reaction employing complexes 6, 7 and 8, as catalysts in the reaction of 2-bromothiophene with boronic acid did not show encouraging signs.