Synthesis and structural characterization of iron–sulfur complexes with hydrophilic nitrogen–phosphorus ligands

PNP-Chelated and -Bridged Diiron Dithiolate Complexes Fe2(μ-pdt)(CO)4{(Ph2P)2NR} Together with Related Monophosphine Complexes for the [2Fe]H Subsite of [FeFe]-Hydrogenases: Preparation, Structure, and Electrocatalysis

“…It is worth pointing out that the phosphorus signals of 2a – c are shifted much upfield by about 5 ppm with respect to those of 2d – f , apparently owing to the stronger electron-donating capabilities of N-alkyl substituents of PNP ligands in 2a – c in comparison to those of the N-aryl substituents in 2d – f . Meanwhile, the 31 P­{ 1 H} NMR spectra of the monophosphine complexes 3a – c show only one singlet at 92.35, 92.71, and 93.96 ppm assigned to the respective coordinated-P atoms, which matches well with the 31 P NMR signals in the range of 90–100 ppm reported in their analogues such as Fe 2 (μ-pdt)­(CO) 5 {κ 1 -Ph 2 P­(NHR)} (R = C 6 H 4 Cl- p , C 6 H 4 NO 2 - p , C 6 H 4 CO 2 Et- p , C 6 H 4 Br- p , C 6 H 4 Me- p ). , …”

“…In addition, the 1 H NMR spectra of 1a – f , 2a – f , and 3a – c all display the typical proton signals in the downfield region of 7.9–6.0 ppm for their phenyl groups and in the upfield region of 2.5–1.6 ppm for their pdt bridges. Obviously, in comparison to those of 1a – f and 2a – f , the 1 H NMR spectra of 3a – c exhibit an additional broad singlet at 5.45 and 5.24 ppm as well as a doublet at 5.78 ppm with the coupling contact 2 J PH = 17.4 Hz for their NH groups, respectively. , This reveals that the molecular structures of 3a – c are distinct from those of 1a – f and 2a – f , which is further confirmed by the following X-ray single-crystal diffraction analysis.…”

“…112 (for 1a−c) or 117 (for 1d−f) ppm attributed to their dibasal and apical−basal isomers, respectively. Such an observation is consistent with the fact that the 31 P{ 1 H} NMR spectra usually contain a strong phosphorus signal in the region of 97−101 ppm for the dibasal isomer and a weak phosphorus signal in the range of 112−118 ppm for the apical−basal isomer, as observed in the similar chelated complexes Fe 26,27 In addition, the 1 H NMR spectra of 1a−f, 2a−f, and 3a−c all display the typical proton signals in the downfield region of 7.9−6.0 ppm for their phenyl groups and in the upfield region of 2.5−1.6 ppm for their pdt bridges. Obviously, in comparison to those of 1a−f and 2a−f, the 1 H NMR spectra of 3a−c exhibit an additional broad singlet at 5.45 and 5.24 ppm as well as a doublet at 5.78 ppm with the coupling contact 2 J PH = 17.4 Hz for their NH groups, respectively.…”

“…Similar reactions of A and the other type of PNP ligands with N-aryl substituents (R = C 6 H 5 , C 6 H 4 OMe- p , C 6 H 4 CO 2 Me- p ) resulted in the obtainment of the target complexes 1d – f in very low yields and the unexpected formation of the monophosphine complexes Fe 2 (μ-pdt)­(CO) 5 {κ 1 -Ph 2 P­(NHR)} ( 3a – c ) as the major products. In addition, although the true reason for the unexpected formation of 3a – c is unclear, we consider that both N-aryl substituents (R) in PNP ligands and water molecules in Me 3 NO·2H 2 O may play an important role in the generation of 3a – c on the basis of the experimental results observed from Schemes and as well as the reported similar cases. − Thus, a possible pathway for the concomitant formation of 3a – c during the preparation of 1d – f is proposed as follows: (i) the reaction of A with 1 equiv of Me 3 NO·2H 2 O in dry MeCN gives the species [Fe 2 (μ-pdt)­(CO) 5 L] ( B , L = NCMe, NMe 3 ), (ii) the intermediate B further reacts with (Ph 2 P) 2 N­(aryl) to afford the species [Fe 2 (μ-pdt)­(CO) 5 {κ 1 -(Ph 2 P) 2 N­(aryl)}] ( C ), , and (iii) the species C undergoes two pathways, with one being observed for the hydrolysis of C with H 2 O to form the monophosphine complexes 3a – c and the other being observed for the intramolecular decarbonylation of C with one free phosphorus atom of the PNP ligand to produce the chelated complexes 1d – f . However, this proposed mechanism needs to be investigated further.…”

Amine‐containing tertiary phosphine‐substituted diiron ethanedithioate (edt) complexes Fe2(μ‐edt)(CO)6‐nLn (n= 1, 2): Synthesis, protonation, and electrochemical properties

“…[ 5,6 ] The Fe2‐P1 bond distances of 1 (2.2153(6) Å) and 3 (2.2217(14) Å) are closer to those observed for Fe 2 ( μ ‐dithiolate)(CO) 5 { κ 1 ‐Ph 2 P(NHR)} with the amine‐containing tertiary phosphines. [ 28,29,32,33,46–50 ] In addition, the P apical ‐Fe‐Fe angles ( i.e. , P1‐Fe2‐Fe1) of 1 and 3 are 4.03 o and 1.73 o are wider than the respective C apical ‐Fe‐Fe ones ( i.e.…”