Photochemical Synthesis of Bis(η‐methyl acrylate)tricarbonyliron

Iron Carbonyl-Promoted Isomerization of Olefin Esters to Their α,β-Unsaturated Esters: Methyl Oleate and Other Examples

“…Figure a also shows the appearance of several new bands, indicating the formation of Fe(CO) 4 (η 2 -CH 3 CH CHCO 2 Me) ( 1 ) and Fe(CO) 3 (η 4 -CH 3 CHCHCO 2 Me) ( 2 ). The bands at 2059 (m), 1991 (s), and 1976 (s) cm -1 are assigned to the ν(CO) absorptions of Fe(CO) 3 (η 4 -CH 3 CH CHCO 2 Me) ( 2 ) by comparing them with ν(CO) bands of the known complex Fe(CO) 3 (η 4 -CH 2 CHCO 2 Me) at 2064 (m), 1994 (s), and 1979 (s) cm -1 (Table ) . The absorptions at 2096 (m), 2029 (s), 2014 (s), and 1991 (s) cm -1 are assigned to the ν(CO) bands of Fe(CO) 4 (η 2 CH 3 CHCHCO 2 Me) ( 1 ) following the previous assignments 19 for this compound.…”

“…To achieve these yields, the following conditions were used: 13 mM olefin ester and 13 mM Fe(CO) 5 in hexanes solvent at 0 °C under UV photolysis for approximately 3 h. Ultraviolet photolysis is necessary to promote the dissociation of the CO groups. This occurs via initial dissociation of one CO group and coordination of the olefin group of the olefin ester to the Fe(CO) 4 unit (eqs 3 and 6). − ,, Additional photolysis removes another CO ligand, which allows the double bond to migrate to the α,β-position and the ester carbonyl group to bind to the metal to give the Fe(CO) 3 (η 4 -α,β-ester) complex. For our conditions, photolysis times shorter than approximately 3 h give lower yields (Table ), because of incomplete reaction between Fe(CO) 5 and the olefin ester (eqs 3, 4, and 6).…”

“…19 Even at -5 °C, Fe(CO) 3 (η 4 -H 2 CdCHCO 2 Me) has been observed in n-hexane where it is in equilibrium with Fe(CO) 3 (η 2 -H 2 CdCHCO 2 Me) 2 , whose concentration depends on the concentrations of the complex and added methyl acrylate. 20,21 These studies suggest that it may be possible to stabilize the R,β-ester isomer of methyl oleate by η 4 coordination to Fe(CO) 3 if the complex (of type A) is produced at relatively low temperatures. This, of course, means that Fe(CO) 5 must catalyze the isomerization at low temperature and that the inexpensive Fe(CO) 5 be used in stoichiometric amount so as to capture the R,β-ester as its η 4 complex.…”

“…Isolable Fe(CO) 3 complexes of η 4 α,β-unsaturated aldehydes (RCHCHC(O)H), ketones (RCHCHC(O)R‘), and imines (RCHCHC(NR‘)H) are well known. ,, The olefin esters, η 4 methyl acrylate and methyl trans -crotonate, also form η 4 complexes, Fe(CO) 3 (η 4 -H 2 CCHCO 2 Me) and Fe(CO) 3 (η 4 -CH 3 CHCHCO 2 Me), that have been detected in ultraviolet-irradiated, low-temperature matrices (10−12 K) containing Fe(CO) 5 and the α,β-unsaturated esters , These studies suggest that it may be possible to stabilize the α,β-ester isomer of methyl oleate by η 4 coordination to Fe(CO) 3 if the complex (of type A ) is produced at relatively low temperatures. This, of course, means that Fe(CO) 5 must catalyze the isomerization at low temperature and that the inexpensive Fe(CO) 5 be used in stoichiometric amount so as to capture the α,β-ester as its η 4 complex.…”

Enantiomeric recognition during cyclopentanone formation with iron(0)

“…Reaction of 2-Methyl-2-norbornene (6) with Fe(CO)s. A reaction mixture containing a 2:1 mole ratio of 2-methyl-2-norbornene to Fe(CO)s was treated according to the general procedure. There was no evidence of olefin iron tricarbonyl complex or cyclopentanone formation after heating for 48 h at 125 °C.…”