Base‐Initiated Formation of Fe^I–PNP Pincer Complexes

Abstract

Fe(I) PNP pincer complexes of the type [Fe(PNPNH)(CO)2]+ were prepared by treatment of the Fe(II) complexes [Fe(PNPNH)(CO)(Cl)2] with KOtBu in an aprotic solvent. The outcome of these reactions is independent of whether it is carried out under a CO atmosphere or not. The tert‐butyl analog [Fe(PNPNH‐tBu)(CO)2]Cl was obtained in a similar fashion but with [Fe(PNPNH‐tBu)(Cl)2] as starting material in the presence of CO. In all these reactions the formation of free PNP ligand together with unknown Fe(III) species is presumably due to a 2FeII → FeI and FeIII disproportionation process. The cationic complexes could be deprotonated upon treatment with KOtBu affording the neutral complexes [Fe(PNPN)(CO)2]. All compounds are low‐spin complexes as established by their solution effective magnetic moments, X‐band EPR spectra as well as DFT calculations. The solid‐state structures of two representative cationic and neutral complexes, respectively, were determined by single‐crystal X‐ray diffraction.

Combining metal–metal cooperativity, metal–ligand cooperativity and chemical non-innocence in diiron carbonyl complexes

“…These EPR results indicate that the paramagnetic center in 4 is a low spin Fe( i ) complex. 25 The calculated spin density plot of a DFT optimized (B3LYP/def2-TZVP) geometry of 4 ( S = ) shows 94% of the positive Mulliken spin density on the iron center (SOMO on d z 2 orbital) ( Fig. 2C ).…”

Structural and Electronic Properties of Iron(0) PNP Pincer Complexes

“…However, the QS values are significantly different. Therefore we calculated the two parameters for the three complexes 4 , 5 and 6 , and for one Fe(I) complex with the same type of pincer ligand, [Fe(PNP NH ‐ i Pr)(CO) 2 ] + ( 7 + ), [12] whose oxygen sensitivity prevented its Mössbauer study, using the ADF program [13] (see Computational details). The calculated QS parameter and the s‐electron density (ρ) at the Fe nucleus are given in Table 1 with the experimental ones for an easy comparison.…”