Metal carbonyl chemistry. Part 29. Preparation and properties of the hydrides [MnH(CO)5–n{P(OCH2)3CEt}n](n= 1,2, or 3)

Abstract

The hydrides cis-[MnH(CO)₄L], mer-trans-[MnH(CO)₃L₂], mer-trans-[MnH(CO)₃(PPh₃)L], and mer-trans- and mer-cis-[MnH(CO)₂L₃][L = P(OCH₂)₃CEt] have been prepared by stepwise substitution of the carbonyl ligands in [MnH(CO)₅]. The corresponding deuterides mer-trans-[MnD(CO)₃L₂] and mer-trans-[MnD(CO)₂L₃] have also been synthesised by substitution in cis-[MnD(CO)₄L], obtained from the reaction between Na[Mn(CO)₄L] and DCl. Infrared and ¹H n.m.r. spectroscopy have shown that while the mono- and bis-phosphite ligand-substituted complexes do not isomerise to any appreciable extent, the compounds [MnX(CO)₂L₃](X = H or D) exist as a ca. 1 : 1 equilibrium mixture of the mer-trans and mer-cis isomers in solution, and on warming above 100 °C in the solid state the pure mer-cis isomer is converted smoothly into the mer-trans isomer. Heating [MnH-(CO)₄L] in solution gives either [{Mn(CO)₄L}₂] or [MnCl(CO)₄L] depending on whether hydrocarbon or chlorinated solvents are used.