Reaction of CpCo(PPh3)2 with diphenylphosphinoalkynes: Syntheses and X-ray structures of 1,3-cyclobutadiene-substituted CpCoCb diphosphine and 2,5-cobaltacyclopentadiene diphosphine dioxide

A potentially bidentate cobalt-containing phosphine ligand, [(η5-C5H5)Co(η4-1,3-(PPh2)2C4Ph2)] (trans-1), was prepared from the reaction between PhCtriple bond; length of mdashCPPh2 and CpCo(PPh3)2 obtained in situ from CoCl(PPh3)3 and NaCp. The cobaltacycle [(η5-C5H5)(PPh3)Co(2,5-(PPh2)2C4H2)] (2) was prepared from the reaction of CpCo(PPh3)2 with HCtriple bond; length of mdashCPPh2. An oxidized product [(η5-C5H5)(PPh3)Co(2,5-(P(O)Ph2)2C4H2)] (4), was obtained upon the attempted isolation of 2 using CTLC. Both 2 and 4 failed to produce [(η5-C5H5)Co(η4-1,2-(PPh2)2C4H2)] or its oxidized analog, respectively, upon thermal activation. The performance of phosphine 1 in the Suzuki coupling of several aryl chlorides with phenylboronic acid in the presence of Pd(OAc)2 was evaluated.