Tricarbonylbis(phosphine)iron(I) Cation Radicals. A Spectroscopic and Theoretical Study

: Comparison of the IR spectra of Fe(CO)3(PPh3)2 and the 17-electron complex [Fe(CO)3(PPh3)2] [PF6], each enriched 50% and 93% with 13CO, shows that the 17-electron d7 radical retains the trigonal-bipyramidal structure (D3hcoordination symmetry) of the parent complex. The IR and EPR spectra of other Fe(CO)3L2+ (L = PMe3, P(n-Bu)3, P(c-C6H11)3) complexes are similar to that of Fe(CO)3(PPh3)2+ with vco= 1974–1999 cm-1 and (g) = 2.053-2.057 (Ap= 17.5-18.7 G). SCF-Xα-DV calculations for the model complex Fe(CO)3(PH3)2+ of D3hsymmetry show a ground-state electronic configuration of 3e“4 (dxzyz) 6e‘3 (dx2-y2xy). The 3e” → 6e’ ”d-d” transition was calculated to occur at 1.06 eV in the near-IR spectral region and was found at 1.16 eV in the electronic absorption spectrum of [Fe(CO)3(PCy3)2][PF6]. An absorption at 1.89 eV in the spectrum of the latter complex is assigned to the dipole-allowed 5a1’→ 6e’ transition, where 5a1’ is the Fe-P σ–bonding orbital. Calculations for assumed C2v and Cssquare-pyramidal isomers of Fe(CO)3(PH3)2+ did not agree with the electronic absorption spectrum of [Fe(CO)3(PCy3)2][PF6]. © 1986, American Chemical Society. All rights reserved.

Duke Scholars

Author Michael J. Therien Chemistry