Substituent control of selective alkali metal ion extraction by amidocrown η3-butadienyl complexes of molybdenum(II)

Substituted η3-butadienyl complexes containing amide-armed crowns (X) of general formula [MoCl(CO)2(η3-CH2C(COX)CCH2)(phen)]n (phen=1,10-phenanthroline) were prepared and investigated for their ability to extract alkali metal ions from a mixed phase system. Reaction of the chlorocarbonyl precursor (1) with 1-aza-15-crown-5, 4′-aminobenzo-15-crown-5, 2-aminomethyl-15-crown-5, 4′-aminobenzo-18-crown-6 or 2-aminomethyl-18-crown-6 gave monomeric complexes (n=1), and addition of sodium tetraphenylboron to the 15-crown-5-substituted complexes gave the corresponding sodium salts. Dinuclear complexes (n=2) were formed by reaction of 1 and 1,7-diaza-15-crown-5 or 4,4′(5′)-diaminobenzo-15-crown-5. Comparison of amidobenzo- and 2-amidomethyl-15-crown-5-substituted complexes showed enhanced sodium transport properties for the latter, and spectroscopic and molecular modeling studies suggested complexation occurred by concerted action of the amide and crown.