877169-11-4

Upstream product

• 603-35-0 triphenylphosphine 
• 877169-10-3 (CH(C(CH₃)NC₆H₃(CH(CH₃)2)2)2)Fe(benzene) 

Relevant academic research and scientific papers

Binding affinity of alkynes and alkenes to low-coordinate iron

We report the synthesis, spectroscopy, and structural characterization of iron-alkyne and -alkene complexes of the type LMeFe(ligand) [L Me = bulky β-diketiminate, ligand = HCCPh, EtCCEt, CH 2CHPh, EtCHCHEt, HCC(p-C6H4OCH3), HCC(p-C6H4CF3)]. The neutral ligand exchanges rapidly at room temperature, and the equilibrium constants have been measured or estimated. The binding affinity toward the low-coordinate Fe follows the trend HCCPh > EtCCEt > CH2CHPh > EtCHCHEt ～ PPh3 > benzene ? N2. This trend is consistent with a model in which π back-bonding from the formally FeI center is the dominant interaction in determining the relative binding affinities. In nitrogenase, alkynes are reduced while alkenes are unreactive, and this work suggests that the different binding affinities to low-coordinate Fe might explain the differential activity of the enzyme toward these two substrates.

Studies of low-coordinate iron dinitrogen complexes

Understanding the interaction of N2 with iron is relevant to the iron catalyst used in the Haber process and to possible roles of the FeMoco active site of nitrogenase. The work reported here uses synthetic compounds to evaluate the extent of NN weakening in low-coordinate iron complexes with an FeNNFe core. The steric effects, oxidation level, presence of alkali metals, and coordination number of the iron atoms are varied, to gain insight into the factors that weaken the NN bond. Diiron complexes with a bridging N2 ligand, LRFeNNFeLR (LR = β-diketiminate; R = Me, tBu), result from reduction of [LRFeCl]n under a dinitrogen atmosphere, and an iron(I) precursor of an N2 complex can be observed. X-ray crystallographic and resonance Raman data for LRFeNNFeLR show a reduction in the N-N bond order, and calculations (density functional and multireference) indicate that the bond weakening arises from cooperative back-bonding into the N2 π* orbitals. Increasing the coordination number of iron from three to four through binding of pyridines gives compounds with comparable N-N weakening, and both are substantially weakened relative to five-coordinate iron-N 2 complexes, even those with a lower oxidation state. Treatment of LRFeNNFeLR with KC8 gives K2L RFeNNFeLR, and calculations indicate that reduction of the iron and alkali metal coordination cooperatively weaken the N-N bond. The complexes LRFeNNFeLR react as iron(I) fragments, losing N2 to yield iron(I) phosphine, CO, and benzene complexes. They also reduce ketones and aldehydes to give the products of pinacol coupling. The K2LRFeNNFeLR compounds can be alkylated at iron, with loss of N2.