The reaction of the diphosphanes 2a-f with (OC),Mo(nbd) technique by using the program EQNMR. Only 3d shows an under high dilution conditions affords the mononuclear ben-interaction with the alkali metal cation Na+ forming a 1:l and zomolybdacrown ethers cis-(OC),Mo( 1,2-, 1,3-, 1,4-2:l complex (3dlcation) while no interaction with Li+ could [Ph2PCH2(CH20CH2),,CH,1,CGH4-~P') (3a-f) (n = 1, 2). On be detected. The molecular structures of 3a and 3d were eluthe basis of the 31P nucleus the inclusion behavior of the mo-cidated by X-ray structural analyses. Complexes 3a and 3d lybdacycles 3a-f toward the alkali metal salts LiBF4 and crystallize in the monoclinic space groups P2,/c and P2,/n NaBPh, was investigated with the aid of a NMR titration with Z = 8 and 4, respectively.