Reactions of Fe(CO)(3) and Fe(CO)(4) with C2Cl(4) in the gas phase monitored by transient infrared spectroscopy: Formation of Fe(CO)(4)(C2Cl4), Fe(CO)(3)(C2Cl4)(2), and novel chloride complexes resulting from the oxidative addition of C2Cl4
Dl. Cedeno et E. Weitz, Reactions of Fe(CO)(3) and Fe(CO)(4) with C2Cl(4) in the gas phase monitored by transient infrared spectroscopy: Formation of Fe(CO)(4)(C2Cl4), Fe(CO)(3)(C2Cl4)(2), and novel chloride complexes resulting from the oxidative addition of C2Cl4, J PHYS CH A, 104(34), 2000, pp. 8011-8026
The gas-phase reactions of Fe(CO)(3) and Fe(CO)(4) with perchloroethylene (
C2Cl4) have been investigated using transient infrared spectroscopy. The ad
dition of C2Cl4 to Fe(CO)(3) produces Fe(CO)(3)(C2Cl4) with a rate constant
of (3.0 +/- 0.8) x 10(-11) cm(3) molecule(-1) s(-1). A second olefin can a
dd to Fe(CO)(3)(C2Cl4) with a rate constant of (1.9 +/- 0.3) x 10(-13) cm(3
) molecule(-1) s(-1) to form the novel bisolefin complex Fe(CO)(2)(C2Cl4)(2
). Absorptions of this complex were identified at 2084 and 2057 cm(-1). C2C
l4 reacts with Fe(CO)(4) with a rate constant of (1.2 +/- 0.3) x 10(-13) cm
(3) molecule(-1) s(-1) to produce Fe(CO)(4)(C2Cl4), which is identified by
its absorptions at 2125, 2069, and 2039 cm(-1). This product isomerizes to
a novel chloride complex via an oxidative addition process, with Arrhenius
parameters E-a = 21 +/- 2 kcal/mol and in A = 28 +/- 2 in the 297-315 K tem
perature range. The chloride complex is best assigned as ClFe(CO)(4)(C2Cl3)
, and possible mechanisms for this isomerization reaction are discussed. Cl
Fe(CO)(4)(C2Cl3) can also be produced by the photolysis of Fe(CO)(4)(C2Cl4)
, and a mechanism for this process is proposed. Absorptions of ClFe(CO)(4)(
C2Cl3) were identified at 2166, 2109, and 2089 cm(-1). Where possible, the
measured rate constants and the observed infrared absorptions are compared
to those for analogous C2H4 and C2F4 complexes. Finally, simulations of a "
global" mechanism for the kinetics of this system are in good agreement wit
h experimental data. From these simulations, Delta G for the isomerization
of Fe(CO)(3)(C2Cl4) to ClFe(CO)(3)(C2Cl3) is estimated to be greater than o
r equal to 4 kcal/mol at 297 K.