Cobalt Carbonyls Stabilized by N,P-Ligands: Synthesis, Structure, and Catalytic Property for Ethylene Oxide Hydroalkoxycarbonylation.

Reactions of N,P-Ligands as Ph 2 P( o -NMe 2 C 6 H 4 ) ( 1 L), 2,6- i Pr 2 C 6 H 3 NHC(Ph)=NC 6 H 4 ( o -PPh 2 ) ( 2 L), and Ph 2 PN(R)PPh 2 (R = i Pr ( 3 L), cyclo -C 6 H 11 ( 4 L), t Bu ( 5 L), CH 2 C 4 H 7 O ( 6 L)) each with dicobalt octacarbonyl produced complexes [ 1 LCo(CO) 3 ] 2 ( 1 ), [ 2 LCo(CO)( μ -CO) 2 Co(CO) 3 ] ( 2 ), [ 3 LCo(CO) 3 ] + [Co(CO) 4 ]‾ ( 3 ), [ 3 LCo(CO) 2 ] 2 ( 4 ), [ 4 LCo(CO) 2 ] 2 ( 5 ), [ 5 LCo(CO) 2 ] + [Co(CO) 4 ]‾ ( 6 ), and [ 6 LCo(CO) 2 ] + [Co(CO) 4 ]‾ ( 7 ). Complexes 1 - 7 have all been structurally characterized by X-ray crystallography, IR spectrometry, NMR spectra, and elemental analysis. Catalytic tests on transformation of ethylene oxide (EO), CO and MeOH into methyl 3-hydroxypropionate (3-HMP) indicate that complexes 1 - 7 are active, where ion pair complexes 3 and 6 - 7 behave more excellently (by achieving 88.4-93.6% 3-HMP yields) than the neutral species 1 - 2 and 4 - 5 (23.7-46.5% 3-HMP yields) when the reactions are all operated at 2 MPa CO pressure and 50 °C in MeOH solvent. Density functional theory (DFT) study by selecting 3 as a model suggests a cooperative catalytic reaction mechanism by [Co(CO) 4 ]‾ and its [ 3 LCo(CO) 3 ] + counterpart. The cobalt-homonuclear ion pair catalysis way is present herein on the EO hydroalkoxycarbonylation.