PREPARATION AND CRYSTAL-STRUCTURE OF A(5)-AZULENE)PENTAKIS-(TRIMETHYLPHOSPHINE)DICOBALT - REACTIONS WITH CARBON-MONOXIDE AND SOLUTION DYNAMICS

Azulene dicobalt complexes 1,2,3,9,10-eta5:4,5,6-eta3-C10H8]Co2(CO)n(P Me3)5-n (n=0 (1); 1 (2); 3 (3)) have been synthesized by reaction of o lefintris(trimethylphosphine)cobalt(0) with azulene under ambient cond itions followed by treatment with stoichiometric amounts or excess of carbon monoxide, respectively. X-ray structural data for 1 show a cycl opentadienyl-type eta5-coordination of a Co(PMe3)2 group and an eta3-a llyl coordination of a Co(PMe3)3 group to the five- and seven-membered rings of azulene, respectively, while a vinylic C=C bond remains unco ordinated. Temperature dependent proton resonances of the azulene liga nd in 1-3 are explained by Co(ligand)3 groups fluctuating between two equivalent sites above the seven-membered ring.