Coordination compounds of olefins with anhydrous silver salts. IV. Complexes with some endocyclic monoolefins

Abstract

A study has been made of the changes in the infrared and nuclear magnetic resonance (n.m.r.) spectra of cyclopentene, cyclohexene, cycloheptene, and cis-cyclooctene, and of their 1-methyl-substituted analogues upon formation of the silver tetrafluoroborate complexes, AgBF4.201efin. Based on the perturbation of the double bond stretching frequency in the olefin, the order of decreasing strength of the silver ion -olefin interaction is cyclopentene > cyclohexene > cis-cyclooctene % cycloheptene.

Magnetic resonance studies of metal–olefin complexes. I. Electron spin resonance spectra of γ-irradiated silver perchlorate cycloalkene complexes

“…Thus a decrease in the spin density on silver accompanies an increase in the size of the cycloalkenyl ring. This parallels the results of the stability of the parent complexes obtained by other methods (8,12). Work in progress includes wide-line nuclear magnetic resonance (n.m.r.)…”

“…Crystalline complexes with a 2:l cycloa1kene:Ag ratio have been obtained with silver nitrate (9, lo), silver perchlorate (9, ll), and silver tetrafluoroborate (12). With a series of cyclomonoolefins, infrared (i.r.)…”

“…and solution p.m.r. studies (11,12) indicate the order of relative stability of the complexes to be: cyclopentene > cyclohexene > cycloheptene 2 ciscyclooctene. This order was found to be virtually independent of the anions used.…”

Magnetic Resonance Studies of Metal Olefin Complexes. II. Electron Spin Resonance Spectra of γ-Irradiated Silver Complexes with Cyclohexadienes and 1-Methyl Cyclopentene

“…The experimental P proton coupling constants of this silver 1-methyl-cyclopentyl radical compare with those assigned to the uncomplexed methyl cyclopentenyl radical (13). This appears to support previous observations that little ring distortion occurs in the complexation (3,14). A comparison of the derived spin densities on the silver ion for the substituted and unsubstituted Ag'methyl-cyclopentenyl radicals (Table 1) reveals an increase in silver spin density with alkyl substitution.…”

“…Uncertainty remains as to whether the steric effects of the 1-alkyl substituent result in a weaker metal-olefin bond or only a larger entropy change for the system upon complex formation. In contrast, Quinn and Van Gilder's infrared studies (3) suggest that a stronger silver-olefin interaction accompanies the increased basicity of cycloalkenes which have an alkyl group at the double bond. Dewar (4) further postulates that there may also be a weakening of the TC component of the coordination bond concurrent with the strengthening of the o component by the electron donating alkyl substituent.…”