Fe-P Bond Research Articles

Preparation and Spectroscopic Characterization of trans-Fe(CO)3L1L2 (L1, L2 = Phosphine or Phosphite)

The 57Fe Mößbauer spectra of mixed ligand complexes of the type trans-Fe(CO)3L1L2 (L1 = triphenylphosphine or triphenylphosphite and L2 = phosphine or phosphite) show a quadrupolesplitting doublet typical of the disubstituted iron carbonyls in trigonal bipyramidal symmetry. The inverse linear dependence of the isomer shifts on the CO stretching frequencies is interpreted on the basis of the strengthening triple-bond nature of the carbonyl ligands with increasing iron-to-phosphorus π-back donation. A linear correlation, with a positive slope, between the isomer shifts and the quadrupole splittings has revealed that the phosphorus-to-iron σ-donation is offset by the iron-to-phosphorus π-back donation. A correlation between the coordination shifts and the isomer shifts demonstrates that the iron-to-phosphorus π-back donation plays an important role in the Fe-P bond. The relatively large coupling constant of 2J(P,P) reflects a strong interaction between trans-phosphorus ligands through the P-Fe-P bond

57Fe Mössbauer and 31P NMR Spectroscopic Characterisation of Fe(CO)3L2 Complexes (L=Phosphite and Phosphine)

Abstract A series of mixed ligand complexes of the type [Fe(CO)3L1L2] (L1=tri-phenylphosphite and L2=phosphine or phosphite) have been prepared to study the Fe-P bond. The 57Fe Mössbauer spectra of trans-[Fe(CO)3L1L2] showed a quadrupole splitting doublet characteristic of the disubstituted iron carbonyls in trigonal bipyramidal symmetry. The linear dependence of the quadrupole splittings on the isomer shifts with a positive slope has revealed that the iron-to-phosphorus σ-donation is offset by the phosphorus-to-iron π-back donation. The 31P{1H} NMR spectra showed a couple of doublets assigned to the coordinated phosphite and the coordinated phosphine. The doublet of the phosphite site was generally observed at the down field compared with that of the phosphine site. The coordination shifts increase with the Mössbauer isomer shifts, suggesting that the iron-to-phosphorus π-back donation plays an important role in the Fe-P bond of trans-[Fe(CO)3L1L2]. The relatively large coupling constants due to 2J(P,P) have demonstrated that there exists a strong interaction between trans phosphorus ligands through the dπ orbitals of the central iron. The coupling constant is a measure of the bond strength between Fe-P, while the Mössbauer isomer shift reflects the electron density at the iron nucleus. Thus, a linear correlation has been established between these two spectroscopic parameters.

ChemInform Abstract: COMPARISON OF THE PHOTOCATALYTIC BEHAVIOR OF PHOSPHINATED POLYMER‐ANCHORED IRON CARBONYL SPECIES AND HOMOGENEOUS PHOSPHINE SUBSTITUTED IRON CARBONYL SPECIES: ALKENE ISOMERIZATION AND REACTION WITH TRIALKYLSILANES

AbstractDie photokatalytische Aktivität von Suspensionen eines Styrol‐1% Divinylbenzol‐Harzes, an dessen Phenylgruppen Diphenylphosphino‐Gruppen eingeführt sind, die wiederum Fe(CO)n‐Gruppen (n: 3, 4) binden, wird mit der photokatalytischen Aktivität von Carbonyltriphenylphosphin‐Fe‐Komplexen Fe(CO)n(PPh3)5‐n inhomogenen Lösungen verglichen, Beide Systeme photokatalysieren die Isomerisierung von Penten‐(1) zu trans‐ und cis‐Penten‐(2) sowie die Reaktion von Penten‐(1) mit Triethylsilan zu Pentan, Pentyl‐triethylsilan, cis‐ und trans‐Penten‐(l)‐yl‐ und trans‐Penten‐(2)‐yl‐triethylsilan.

Comparison of the photocatalytic behavior of phosphinated polymer-anchored iron carbonyl species and homogeneous phosphine substituted iron carbonyl species: alkene isomerization and reaction with trialkylsilanes

Abstract : A styrene-1% divinylbenzene resin whose phenyl rings have been derivatized with --PPh2 groups serves as an 'anchor' for Fe(CO)(n)(n = 3,4) groups; the anchor is the Fe-P bond. The photocatalytic activity of suspensions of the polymer-anchored Fe(CO)(n) has been compared to homogeneous solutions of Fe(CO)(n)(PPh3)(5-n)(n = 5,4,3). 1-Pentene isomerization and reaction with HSiEt3 can be effected with each system. Observed quantum yields for 1-pentene isomerization exceed unity for each catalyst precursor and the initial trans- to cis-2-pentene ratio depends on the catalyst precursor implicating the retention of the triarylphospine groups in the actual catalytically active species. Irradiation of Fe(CO)n(PPh3)(5-n)(n = 4) results in loss of CO, not PPh3, suggesting a photoinert anchor to the Fe(CO)n groups in the polymer systems. These experiments establish the viability of photogenerating catalysts anchored to polymer supports without destruction of the the anchor bond in the photogeneration procedure. (Author)