An EPR Study of 2,3-Bis(diphenylphosphino)maleic Anhydride (BMA) Complexes and the BMA Radical Anion.

EPR spectra are reported for four metal complexes of 2,3-bis(diphenylphosphino)maleic anhydride (BMA), [Co(2)(PhCCR)(CO)(4)(eta-BMA)](-), R = Ph, H, [Co(2)(PhCCPh)(CO)(4)(&mgr;-BMA)](-), and [PhCW(CO)(2)(BMA)Cl](-), as well as the radical anions, [BMA](-) and [BPCD](-), BPCD = 4,5-bis(diphenylphosphino)cyclopentene-1,3-dione. At room temperature, all spectra are 1:2:1 triplets due to hyperfine coupling to two equivalent (31)P nuclei with coupling to two equivalent (1)H nuclei for [BPCD](-) and unresolved coupling to one or two (59)Co nuclei for the Co complexes with chelating or bridging BMA, respectively. The (31)P couplings are temperature dependent, ca.