The coordination of small molecules by manganese(II): III. The reversible binding of carbon monoxide by MnX 2(PR 3) (R 3  PhMe 2, PhEt 2, Pr n.3, X  Cl, Br, I) in the solid state and in solution

Abstract

The manganese(II) phosphine complexes MnX 2(PR 3)(PR 3  PPhMe 2, X  Cl, Br, I; PR 3  PPhEt 2, PPr n 3, X  Cl, Br) have been found to react with carbon monoxide in a 1/1 ratio to form “MnX 2(CO)(PR 3)” in the solid state and in tetrahydrofuran (THF) solution. The reaction may be reversed either by a pressure drop or a temperature rise, and the gas released is shown to be carbon monoxide by mass spectral methods. The rate of reaction of MnX 2(PR 3) with carbon monoxide appears to be both phosphine and halide dependent. In THF solution ESR measurements indicate that the CO adduct is the pseudooctahedral MnX 2(THF) 2(CO)(PR 3 species, whereas in the solid state it is the pseudotetrahedral MnX 2(CO)(PR 3). The ν(CO) infrared band appears at 2100–2085 cm −1 in the carbon monoxide adducts.