What is the nature of bonding in [Fe(CO)3(NO)]− and [Fe(CO)4]2−?

Maja Gruden,Matija Zlatar

doi:10.1007/s00214-020-02639-3

Abstract

To shed new light on the electronic structure of [Fe(CO)3(NO)]¯ complex ion, DFT-based analysis of the nature of chemical bonding has been performed. For this purpose, the extended transition state energy decomposition analysis alongside the natural orbitals for chemical valence has been used and results are compared to the nature and the strength of the interactions in isoelectronic [Fe(CO)4]2− complex ion. Based on orbital contribution to the interaction energy and charge flow between the fragments, the ground state can be best described as an open-shell singlet with zero formal oxidation state on iron and negative charge on the nitrosyl ligand. It is in agreement with the different nature of interactions when NO+ and CO ligands are bonded to Fe(−II).

Highlights

Maja Gruden1,* and Matija Zlatar2,* 1 University of Belgrade - Faculty of Chemistry, Studentski trg 12-16, 11000
ΔQ 0.46 a 0.45 a a charge is transferred from [Fe(CO)3]2− fragment to CO fragment i) [Fe(CO)3]2−--NO+ 126.23 -215.90 -356.01 -2.07 -447.74 57.14 -94.61 1.21a ii) 2[Fe(CO)3] ̄-- 2NO 172.73 -91.94 -124.72 -2.67 -46.59 17.69 -28.92 0.46b iii) 3[Fe(CO)3]-- 3NO 196.67 -177.83 -94.16 -3.13 -78.46 5.6 -28.92 0.29c i) closed-shell singlet [Fe(CO)3NO] ̄ ii) and iii) open-shell singlet with “non-aufbau” occupation of KSMOs [Fe(CO)3-NO] ̄ a charge is transferred from [Fe(CO)3]2− fragment to NO+ fragment b charge is transferred from [Fe(CO)3] ̄ fragment to NO fragment c charge is transferred from NOfragment to [Fe(CO)3]
I) [Fe(CO)3]2−--NO+ 92.11 -204.08 -333.58 -445.45 61.54 -31.54 1.29a ii) 2[Fe(CO)3] ̄-- 2NO 158.09 -86.58 -161.75 -90.24 40.65 -49.55 0.52b iii) 3[Fe(CO)3] -- 3NO 188.12 -172.09 -98.52 -82.50 9.1 -49.55 0.23c i) closed-shell singlet [Fe(CO)3NO] ̄ ii) and iii) open-shell singlet [Fe(CO)3-NO] ̄ a charge is transferred from [Fe(CO)3]2− fragment to NO+ fragment b charge is transferred from [Fe(CO)3] ̄ fragment to NO fragment c charge is transferred from NOfragment to [Fe(CO)3]