Conductivity studies of ion pairing in transition metal organics

Abstract

The dependence of equivalent conductances on the concentration of T H F solutions of (q5-C5H5)Fe(C0)3+BPh4-, (q5-C S H~) F~( C O )~P M~~P~+ B P~~-, (Ph3P)zN+HFe(CO)4-, Et4N+(pH) [Cr(CO)s] 2-, and Li+Mo(CO)5C(O)Ph-and of CH3CNsolutions of (q5-C5H5)Fe(CO)2PMe2Ph+BPh4-, (s6-C6H6)Mn(C0)3+BPh4-, and (116-C6H6)Mn(CO)3+C104-were analyzed according to the Fuoss and Fuoss-Hsia equations. Ion-pair dissociation constants, KD, of -10-5 were found for the cyclopentadienylmetal carbonyl salts in THF; the large cations Et4N+ and (Ph3P)2N+ were found to be as associated to metal carbonyl anions as were the alkali metal solvates, Li(THF),+ or Na(THF),+. A stronger ion pair was observed for the lithium acylate as indicated by a K D on the order of Dissociation constants of approximately determined for the cyclopentadienyl-and arenemetal carbonyls are among the smallest ever reported for salts in acetonitrile. Exact sites of ion interaction were not discernible in this study; however ion center-to-center distance parameters indicated that all of the salts studied in T H F existed as contact ion pairs.