Tungsten complexes of aromatic and aliphatic thioaldehydes

Abstract

Reaction of PPN[W(CO) 3(R 2PC 2H 4PR 2)(SH)] (PPN=Ph 3PNPPh 3; R=Me, 1; R=Ph, 2) with aromatic aldehydes in the presence of trifluoroacetic acid gave tungsten complexes of thiobenzaldehydes mer-[W(CO) 3(R 2PC 2H 4PR 2)(η 2-SCHR ′)] (R=Me, 3a– 3f; R=Ph, 4a– 4e) in high yields. Analogous complexes of aliphatic thioaldehydes mer-[W(CO) 3(Me 2PC 2H 4PMe 2)(η 2-SCHR ′)] ( 3g– 3l) could only be obtained from the highly electron-rich thiolate complex 1. The structure of 3i (R ′= i-Bu) was determined by X-ray crystallography. In solution the complexes 3 and 4 are in equilibrium with small quantities of their isomers fac-[W(CO) 3(R 2PC 2H 4PR 2)(η 2-SCHR ′)]. Reaction of complexes 3 with dimethylsulfate followed by salt metathesis with NH 4PF 6 gave the alkylation products mer-[W(CO) 3(Me 2PC 2H 4PMe 2)(η 2-MeSCHR ′)]PF 6 ( 5a– 5l) as mixtures of E and Z isomers. The methylated thioformaldehyde complex mer-[W(CO) 3(Me 2PC 2H 4PMe 2)(η 2-MeSCH 2)]PF 6 ( 5m) was prepared similarly. Nucleophilic addition of hydride (from LiAlH 4) to 5 initially gave thioether complexes mer-[W(CO) 3(Me 2PC 2H 4PMe 2)(MeSCH 2R ′)] ( mer- 6) which rapidly isomerized to fac-[W(CO) 3(Me 2PC 2H 4PMe 2)(MeSCH 2R ′)] ( fac- 6).