Investigation of the monomer-dimer equilibria of molybdocenes in water

Molybdocenes form monomeric and dimeric complexes upon dissolution in water . The solution structures of the molybdocenes at neutral pH are inferred as the monomeric [(CpR)(2)Mo(OH2)(OH)](+) and the dimeric [(CpR)(2)Mo(mu-OH)( 2)Mo(CpR)(2)](2+). The equilibrium constants for the monomer-dimer equilibr ia were obtained from H-1 NMR dilution studies as K'(eq) = (7.9 x 10(-2)) /- (1.0 x 10(-3)) M for R = CH3 at pD 7 and as K-eq = (3.5 x 10-2) +/- (1.3 x 10(-3)) M for R = CH3 at pD 3.5. Qualitatively, the monomer of the CpMe molybdocene is more favored than the Cp analogue, compared to their respect ive dimers.