Multinuclear NMR of cis-dicarbonylbis(dithiocarbamato)iron(II) complexes in chloroform solution

Abstract

The 13C and 15SN NMR spectra of eleven cis-Fe(S 2CNRR′) 2(CO) 2 complexes, where R and R′ are organic substituents, have been measured at ambient temperature in CDCl 3 (0.08–0.16 M). The 13C absorptions for the carbonyl ligands correlate well with the force constants for the CO stretching vibrations in CHCl 3 solution. Each of the parameters ( 13CO absorption and k cis for CO) correlate well with the aqueous solution p K a for +H 2NRR′, corrected for the phenyl-containing substituents, high p K a values corresponding to high 13CO absorptions and low k cis CO force constants. [p ]Evidence was found in the 13C NMR spectra for hindered rotation about the CN bond in S 2CNC 2 in complexes with higher p K a(corr) values and in the 13C spectra of the corresponding thiuram disulfides. [p ]The 15N (natural abundance) NMR spectra for each of the complexes was determined. Each revealed a single sharp absorption in a region of the 15N NMR spectrum which indicates substantial CN double bond character, as one would expect for coordinated dithiocarbamate ligands.