The effect of fluorine, trifluoromethyl and related substitution on the donor properties of triarylphosphines towards [Fe(CO)4]

Homogeneous Catalysis in Supercritical Carbon Dioxide

“…The phosphines P(4-CF 3 C 6 H 4 ) 3 and P(3-CF 3 C 6 H 4 ) 3 showed identical electronic behavior and almost identical activity/selectivity behavior, while P[3,5-(CF 3 ) 2 C 6 H 3 ] 3 , with a much higher ν(CO) value, also had a significantly higher activity. The results were in agreement with an earlier report that the electronic effect of trifluoromethyl substitution is independent of ortho, meta, or para placement and that the effects of multiple trifluoromethyl substitutions are cumulative (42). The ability of oxygen and methylene groups to insulate against the electron withdrawing effects of the fluoroalkyl moieties could be observed for phosphines P(4-CF 3 OC 6 H 4 ) 3 and P[4-F(CF 2 ) 4 (CH 2 ) 3 C 6 H 4 ] 3 , where significant decreases in ν(CO) were accompanied by 50% and 70% decreases in activity, respectively.…”

“…The rate of hydroformylation correlated very well with the IR stretching frequency of metal carbonyls, ν(CO), for the various catalysts, showing a linear dependence. The ν(CO) is a sensitive indicator of electron density at the metal center, yielding a relative measure of the amount of π-back-bonding from an occupied metal d orbital to the empty π * orbital of the carbonyl (41)(42)(43). The trend in ν(CO) corresponded well with the amount and proximity of the electron-withdrawing fluoroalkyl or fluoroalkoxy groups of the phosphines, with P[3,5-(CF 3 ) 2 C 6 H 3 ] 3 having the greatest effect and P[4-F(CF 2 ) 4 (CH 2 ) 3 C 6 H 4 ] 3 having the least effect relative to the value for PPh 3 .…”

Iron carbonyl complex containing bis[2‐(diphenylphosphino)phenyl]ether enhancing efficiency in the palladium‐catalyzed Suzuki–Miyaura reaction

“…It may be mentioned that the majority of structurally characterized Fe(CO) 4 (phosphine) complexes showed that the phosphine group occupied the axial position . To the best of our knowledge, only two structures appeared in the literature in which phosphine occupied the equatorial position . Since we could not develop diffraction‐quality crystals for X‐ray analysis, we carried out a geometry optimization study for complex 1 using a DFT method.…”

Tetracarbonyl(tricyclohexylphosphine)iron(0)

“…All of these compounds show similar molecular structures to (I), with a trigonal-bipyramidal ligand arrangement and the phosphine adopting one of the axial positions. Nevertheless, there is one compound with a P-Fe-C(trans) bond angle of only 143.9 (Howell et al, 1998), presumably due to a very bulky phosphine ligand with ortho-isopropylphenyl substituents. It is remarkable that the Fe-P bond length in (I) is almost the longest that has been reported until now.…”

“…It is remarkable that the Fe-P bond length in (I) is almost the longest that has been reported until now. Only the abovementioned derivative with a tris(ortho-isopropylphenyl)phosphine (2.289 Å ; Howell et al, 1998), the complex with a tri-tert-butylphosphine ligand (2.363 Å ; Pickardt et al, 1976), the compound exhibiting a tris(ortho-methylphenyl)phos-phine ligand (2.306 Å ; Howell et al, 1991Howell et al, , 1993) and a trinuclear iron-carbonyl compound in which a diphenylphosphine ligand bearing a coordinated methoxycarbonylethenyl group is attached to an Fe(CO) 4 group (2.283 Å ; Montio et al, 1990) show similar or even slightly longer Fe-P bonds.…”