Synthesis and spectroscopic studies of organometallic Mn(I) complexes containing the novel mixed donor ligands 2-{MeSeCH(2−n)(SiMe3)n}C5H4N (n=0–2)

Treatment of MnBr(CO)5 with one equivalent of the bidentate ligand, 2-{RECH(2−n)(SiMe3)n}C5H4N (E=S, R=Me, Ph, n=0; E=Se, R=Me, n=0, 1, 2) affords the complexes [MnBr(CO)3L] as orange powders. The effect of stepwise substitution at the α-carbon of the ligand by a trimethylsilyl group was investigated using 77Se{1H}- and 55Mn-NMR, and IR spectroscopies. In the case of the pyridyl-selenoether-containing complexes, each additional Me3Si− group increases the σ-donating properties of the ligand, in turn reflected in increased Mn→CO backbonding. The solid-state structure of the parent [MnBr(CO)3{2-(PhSCH2)C5H4N}] showed the molecule to have distorted fac-octahedral geometry. All other compounds were assigned the same stereochemistry based on CO stretching frequency comparisons.Substitution at the α-carbon and variation of the Group 16 centre and terminal substituent of the chalcogenoether can vary the electronic properties of the metal centre in manganese carbonyl bromide complexes containing the ligands L. 77Se{1H}- and 55Mn-NMR spectroscopies and IR spectroscopy have been used to investigate the solution characteristics of these compounds.