Olefin hydrogenation with iron carbonyls as catalysts

Abstract

[Fe 3(CO) 12 ] as cat a lytic pre cur sors in the hy dro gena tion re ac tions of cyclohexene and 1-hexene was in ves ti gated. A pho to chem i cal re ac tor with H2 flux and UV-vis con tin u ous ir ra di a tion was used for these stud ies. The in fra red spec tra of the sam ples showed the for ma tion of [Fe(CO) 4(ole fin)] and [HFe(CO) 3(π-allyl)] as in ter me diates. The ac tiv ity of [Fe 2(CO) 9] in the hy dro ge na tion of cyclohexene was higher (66.6%) than the ac tiv ity of the other iron car bon yls (43.0% [Fe(CO) 5], [Fe 3(CO) 12 ]). The com pe ti tion between isomerization and hy dro ge na tion in the re ac tion of 1-hexene was stud ied. The isomerization rate was much higher than the hy dro ge na tion rate and the polynuclear spe cies pro vided faster isomerizations than [Fe(CO) 5]. The alkane con ver sions were: 60.0% ([Fe(CO) 5], [Fe 3(CO) 12 ]) and 75.4% ([Fe 2(CO) 9]), show ing that for the 1-hexene hy dro ge nation [Fe 2(CO) 9] also ex hib ited the high est ac tiv ity. Key words: iron car bon yls, ole fin hy dro ge na tion, ca tal y sis In tro duc tionThe util ity of [Fe(CO) 5 ] and [Fe 3 (CO) 12 ] as photocatalysts in the hy dro ge na tion of alkenes has been known since the 1970s [1][2][3][4] . Many un sat u rated de riv a tives are pro duced in these re ac tions via the loss of CO groups from the iron car bon yls, and the ac tual cat a lyst is prob a bly a re duced car bonyl spe cies, such as [Fe(CO) x ] or [Fe(CO) 3 ] 5-10 . Sur pris ingly, the photocatalytic ac tiv ity of the dinuclear com pound [Fe 2 (CO) 9 ] has never been in ves ti gated. In this pa per, we re port our studies on the photocatalytic ac tiv ity of [Fe 2 (CO) 9 ] in the hy dro gena tion of cyclohexene and 1-hexene. Fur ther more, com par a tive stud ies of the photocatalytic ac tiv i ties of [Fe(CO) 5 ] and [Fe 3 (CO) 12 ] in these pro cesses were also performed. Ex per i men talA pho to chem i cal re ac tor made of Py rex 11 was used, and a mer cury va por lamp (125 W) was adapted to the re actor.The re ac tions were con ducted un der H 2 flux (P[H 2 ] = 1 atm), at 0 °C, un der con tin u ous ir ra di a tion. All of the prepa ra tory steps were un der taken un der Ar at mo sphere, and the re ac tor was purged with Ar for five min utes be fore use.[Fe(CO) 5 ] was sup plied by BASF. [Fe 2 (CO) 9 ] and [Fe 3 (CO) 12 ] were pre pared as de scribed in the lit er ature 12,13 . The to lu ene so lu tions were 0.01 M in iron and 0.1 M in the ole fin (cyclohexene or 1-hexene). The same iron atom Ar ti cle

Mechanism of Iron Carbonyl-Catalyzed Hydrogenation of Ethylene. 1. Theoretical Exploration of Molecular Pathways

“…Coordinatively unsaturated transition metal (TM) carbonyls are known to catalyze various processes, primarily the hydrogenation, isomerization, and hydroformylation of olefins, − C–H bond activation, and Fischer–Tropsch and water–gas-shift reactions. ,, Iron carbonyls are widely used in manufacturing new materials and epitaxial layers . Fe(CO) 5 is particularly used in preparation of carbon nanotubes via the catalytic chemical vapor deposition, where molecular hydrogen plays an important role in the growth and microstructure of nanotubes .…”