Variable temperature electronic spectra of the two low spin five-coordinate cobalt(I) complexes [CoI(CO)2{P(C6H5)(OC2H5)2}3][B(C6H5)4] and CoII(CO)2{P(C6H5)(OC2H5)2}2

Solution and solid state electronic spectral measurements at 295, 77 and 7° K, have been carried out on the low spin five-coordinate [COI(CO)2{P(C6H5)(OC2 H5)2}3][B(C6H5)4] (I) and COII(CO)2{P(C6H5)(OC2 H5)2}2(II). The presence of two moderately intense ligand field bands at respectively 27.4 (εEPA = 420) and 30.5 kK (εEPA = 980) for (I) and 22.6 (εEPA = 650) and 26.0 kK (εEPA = 1700) for (II) is consistent with a trigonal bipyramidal geometry of C2v symmetry for both complexes. Allowed I»Co(I) charge transfer bands are observed at 29.0 kK and 34.5 kK for (II), whereas an allowed P(C6H5)(OC2H5)2»Co(I) is found at 39.6 kK for (1) and 40.0 kK for (II). © 1975.