Electrochemical and metathetical preparations of isomers of bis-(cyanotrihydroborato)tetrakis(trialkyl phosphite)iron(II) complexes, [Fe{BH3(CN)}2{P(OR)3}4]

Abstract

Iron(II) complexes of the general formula [Fe{BH₃(CN)}₂{P(OR)₃}₄](R = Me or Et) have been prepared both metathetically, by the reaction of FeCl₂.2H₂O with Na[BH₃(CN)] and the appropriate phosphite, in either methanol or acetonitrile, or electrochemically by the anodic dissolution of iron in acetonitrile solutions of the phosphite and Na[BH₃(CN)]. The metathetical reactions carried out in methanol give the trans isomers only, as shown by the ¹H n.m.r., ³¹P-{¹H} n.m.r., and i.r. spectra of the products. In acetonitrile, the metathetical reactions yield mixtures of isomers in the cis: trans ratio of ca. 30 : 70, as shown by ¹H n.m.r. and i.r. spectra, supported by thin-layer chromatographic analysis. For R = Me, the electrochemical reaction in acetonitrile yields a mixture containing ca. 65% of the cis isomer. Where R = Et however, the cis content is ca. 30%. These observations are discussed.