Tungsten(IV) bis(acetylacetonate) (acetylacetonate = acac) complexes were synthesized by incorporating either a diazoalkane or an oxo ligand into the coordination sphere of a tungsten(II) reagent. The reaction of free diazoalkane (N 2CRR′) with W(CO) 3(acac) 2 leads to loss of two carbon monoxide ligands and coordination of the diazoalkane reagent through the terminal nitrogen to produce W(CO)(acac) 2(N 2CRR′). This monomer is best formulated as a tungsten(IV) complex. A second example of converting a d 4 tungsten carbonyl complex to a d 2 product involves oxidation of W(CO)(acac) 2(PhC≡N) with m-chloroperoxybenzoic acid (MCPBA) to replace the CO ligand with an oxygen atom. This increase in metal oxidation state causes rotation of the nitrile ligand by 90° relative to the two bidentate acac ligands. Electrophilic addition at the nitrogen of the π-bound nitrile ligand using methyl triflate (MeOTf) and subsequent nucleophilic addition at carbon with sodium trimethoxyborohydride, Na[HB(OMe) 3], reduces the C≡N bond stereoselectively and produces the neutral imine complex W(O)(acac) 2(PhHC=NMe) with a diastereomeric ratio of 11:1.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry