Studies on olefin-coordinating transition metal carbene complexes: XX. Synthesis of 1,3-cyclohexadiene(dicarbonyl)[ethoxy(aryl)-carbene]iron complexes and their phosphine adducts. Crystal structure of C 6H 8(CO) 2FeC(OC 2H 5)C 6H 4CH 3- o

Abstract

Reaction of 1,3-cyclohexadiene(tricarbonyl)iron ( 1) with ortho-substituted aryllithium reagents ArLi (Ar o-CH 3C 6H 4, o-CH 3OC 6H 4, o-CF 3C 6H 4) in ether at low temperature, and subsequent alkylation of the acylmetalates formed with Et 3OBF 4 in aqueous solution at 0°C or in CH 2Cl 2 at −60°C gave the 1,3-cyclohexadiene(dicarbony)[ethoxy(aryl)carbene]iron complexes (η 4-C 6H 8)(CO) 2FeC(OC 2H 5)Ar ( 3, Ar  o-CH 3C 6H 4; 4, Ar  o-CH 3OC 6H 4), and the isomerized product (η 3-C 6H 8)(CO) 2FeC(OC 2H 5)C 6H 4CF 3- o ( 5), respectively, among which the structure of 3 has been established by an X-ray diffraction study. Complex 3 is monoclinic, space group P2 1 with a = 8.118(4), b = 7.367(4), c = 14.002(6) Å, β = 104.09(3)°, V = 812.2(6) Å 3, Z = 2, D c = 1.39 g cm −3 , R= 0.056, and R w = 0.062 for 976 observed reflections. Complexes 3 and 5 were converted into the chelated allyliron phosphine adducts (η 3-C 6 H 8)(CO) 2(PR 3 1)FeC(OC 2H 5)Ar ( 6, Ar  o-CH 3C 6H 4, R 1  Ph; 7, Ar  o-CH 3C 6H 4, R 1  OPh; 9, Ar  o-CF 3C 6H 4, R 1  Ph), by reaction with phosphines in petroleum ether at low temperatures.