Tripod ligands of constitutional C1 symmetry containing a deliberate set of mixed P/S donor groups: Synthesis and coordination chemistry

Article abstract of DOI:10.1016/S0020-1693(97)05784-8

Various efficient strategies for the preparation of tripod ligands with mixed P/S donor sets such as H₃CC(CH₂PPh₂) (CH₂SR) (CH₂SR′) (6) or three different S donors H₃CC(CH₂SR)(CH₂SR′)(CH ₂SR″) (5) are described. Compounds 5 are capable of acting as tridentate chelate ligands in complexes such as [H₃CC(CH₂SEt)(CH₂SⁱPr)(CH ₂S^tBu)Mo(CO)³] (9b). Quite alike compounds 6 act as tripod ligands as evidenced by the isolation and structural characterization of three derivatives [H₃CC(CH₂PPh₂)(CH₂SR)(CH ₂SR′)Mo(CO)₃] (11a, 11c, 11e). It is shown that under 1 bar CO substitution of one SR group by CO occurs to give [H₃CC(CH₂PPh₂)(CH₂SR)(CH ₂SR′)-Mo(CO)₄] (12). With 11a, [H₃CC(CH₂PPh₂)(CH₂SPh)(CH ₂SBn)Mo(CO)₃], as the starting compound the carbonylation gives exclusively 12a with the CH₂SPh group playing the role of the dangling arm. All the new compounds are fully characterized by NMR and mass spectrometric techniques as well as by IR spectra and cyclovoltammetric data and X-ray analysis for the coordination compounds.