Chemistry of polyfunctional molecules CXXXII. Synthesis and crystal structure of a paramagnetic five-fold coordinated cobalt(III) complex from Co-2(CO)(8), Ph2P-N=PPh2-PPh2=N-PPh2, and air

The reaction of Co-2(CO)(8) and Ph2P-N=PPh2-PPh2=N-PPh2 (1) in a molar rati o between 1:1 and 1:3 in toluene always leads to the formation of both the yellow by-product [fac-Co(CO)(3)(Ph2P-N=PPh2-PPh2=N-PPh2-P,P')] [Co(CO)(4)] (4) and the red compound [(Co)(2)(mu-CO)(CO)(4)(mu-Ph2P-N-PPh2)(2)] (5) th at has already been characterized by spectroscopic data and Xray analysis. Whereas 4 is obtained as a precipitate, the red compound 5 stays in solutio n and reacts in presence of air with the remaining ligand 1 in a non-stoich iometrical reaction to the violet cobalt(III) complex [Co(eta(1)-O-PPh2=N-P Ph2=O)(eta(2)-O-PPh2=N-PPh2=O)(2)] (6). The crystal structure of 6 proves a distorted trigonal bipyramidal coordination of the oxygen atoms at the Co( III) ion. Surprisingly, complex 6 shows an unusual paramagnetism according to four unpaired electrons (5.21+/-0.04 BM).