Neuartige basische liganden für die homogenkatalytische methanolcarbonylierung: V. Komplexchemisches verhalten mehrzähniger furfurylphosphane und ihr einfluss auf die selektivität und den umsatz bei der ethanolsynthese aus methanol

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The potentially four-, three- and bidentate furfurylphosphanes RP(CH 2C 4H 3O) 2 ( 3a–e) (R  Ph ( a), Mes ( b), Me ( c), t-Bu ( d), CH 2C 4H 3O ( e), et ( f)) and Ph 2PCH 2C 4H 3O ( 5) react with (OC) 5WTHF to give the pentacarbonyltungsten complexes (OC) 5WPR(CH 2C 4H 3O) 2 ( 4a–e) and (OC) 5WPPh 2CH 2C 4H 3O ( 6), respectively. Irradiation of ether solutions of 4a–e and 6 leads to the formation of the tetracarbonyltungsten complexes (OC) 4WPR(CH 2C 4H 3O) 2 ( 8a–e) and (OC) 4WPPh 2CH 2C 4H 3O ( 9), respectively. In a similar way (OC) 4WPPh 2C 2H 4C 4(CH 3)H 2O ( 10) is obtained from Ph 2PC 2H 4C 4(CH 3)H 2O ( 1) and (OC) 5WTHF via the intermediate compound (OC) 5WPPh 2C 2H 4C 4(CH 3)H 2O ( 7). Furyl-oxygenmetal interactions do not occur. Only one furyl ring is η 2-bonded to the metal in 8a–e, 9 and 10. As was exemplified by 8e and 9 this very weak bond is easily cleaved by phosphanes. The influence of the furfurylphosphanes 1, 3a–f and their phosphonium salts [RP(CH 2C 4H 3O) 3]Br ( 13a,d,e), [EtP(CH 2C 4H 3O) 3]I ( 13f) and [Ph 2P(CH 2C 4H 3O) 2]Br ( 14) and of hte furylphosphanes RP(C 4H 3O) 2 ( 15a,c,d) and Ph 2PC 4H 3O ( 16) on the homologation of methanol to ethanol was investigated using cobalt as a catalyst metal and iodine as a promotor. In accordance with their complex chemical behaviour the best results with respect to selectivity and conversion were obtained with the bidentate ligands 5 and 16.