Reaction of Carbon Monoxide with Iron(II) Thiolates. Preparation and Structure of fac‐[Na(15‐Crown‐5)][Fe(CO)3(SPh)3] and fac‐[K(18‐Crown‐6)][Fe(CO)3(SPh)3]

Abstract

Solutions of Fe(II) and thiolates (RS‐: Fe²⁺ > 2; R = alkyl, phenyl) absorb carbon monoxide and ‐ depending on the reaction conditions ‐ several different anionic iron carbonyl derivatives are formed. Two of these complexes, fac‐[Na(15‐crown‐5)][Fe(CO)₃(SPh)₃] (1) and fac‐[K(18‐crown‐6)][Fe(CO)₃(SPh)₃] (2) were isolated and their crystal structures determined. (1) Crystallizes in the triclinic space group P1 with a = 11.915(3)Å, b = 12.391(3)Å, c = 14.337(3)Å, α = 65.77(5), β = 116.28(5)°, γ = 105.87(5)°, V = 1720(1)ų, Z = 2, d_calcd = 1.30 gcm⁻³; (2) crystallizes in the cubic space group Pa3, with a = 19.609(4)Å, V = 7540(3)ų, Z = 8, d_calcd = 1.4 gcm⁻³. Final agreement factors were R = 0.092, R_w = 0.102 (3919 reflections with F>7σ(F)) for (1); and R = 0.069, R_w = 0.050 (1125 reflections with F>4σ(F)) for (2). Both [Fe(CO)₃(SPh)₃]⁻ anions of 1 and 2 have the same octahedral ligand arrangement with the carbonyl ligands cis to each other and trans with respect to the thiolato ligands. In complex 2 the K⁺ lies on the crystallographic threefold axis and is therefore exactly equidistant (3.475(2)Å) from the three sulphur atoms; on the contrary in complex 1 in the Na⁺ is nearer to two of the three sulphur atoms (3.083(6)Å and 3.334(6)Å for the two different Na…S distances). The infrared spectra of the compounds were recorded in a variety of solvents and in the solid state. The Raman of crystalline 2 was also recorded. The failure of the vibrational spectra of crystalline 2 to follow either molecular point group or factor group predictions is explained in terms of an effective vibrational unit ‐ and so, effective factor group ‐ similar to that implicit in a factor group analysis of 1.