Electronic structure and properties of MCO and M5CO carbonyls (M = Fe, Ni, Cu) by density functional methods

Abstract

Density functional theory (DFT) calculations of the electronic structure and properties of Fe, Ni, and Cu carbonyls with one and five transition‐element atoms are reported, due to their importance in heterogeneous catalysis (especially in Fischer‐Tropsch synthesis). The local density approximation (LDA) with the Vosko‐Wilk‐Nussain (VWN) correlation functional as well as the generalized gradient approximation (GGA) using Becke's 1988 exchange functional and Perdew's 1986 correlation functional (BP method) were applied to the study of the clusters using a triple‐zeta plus polarization (TZP) basis set. Triplet and quintuplet states for FeCO, singlet and triplet for NiCO, and doublet for CuCO were considered, and optimization of energy at the LDA/BP level for these cases was done. Dissociation energies in M and CO fragments, frequencies, and population analysis were performed. Geometry optimization of the distance between the C atom and the clusters M5 (with geometries taken from the crystals) were carried out and the dissociation energy in fragments M5 and CO as well as population analysis at the optimized geometries were also done. Comparison between our results and some others published using ab initio and density functional methods were performed. © 1996 John Wiley & Sons, Inc.

Spectroscopic and Theoretical Investigations of Vibrational Frequencies in Binary Unsaturated Transition-Metal Carbonyl Cations, Neutrals, and Anions

“…On the theoretical side, there has been long discussion on the ground state of FeCO. ,− ,− Berthier and co-workers found 3 Σ - to be the ground state, with a 5 Σ - state lying 12 kcal/mol higher in energy using the CIPSI method . At the MCPF level, the quintet state was predicted to be 1.6 kcal/mol more stable than the triplet state .…”

Infrared Photodissociation Spectroscopy of Mass Selected Homoleptic Copper Carbonyl Cluster Cations in the Gas Phase

“…Matrix isolation experiments show that the Cu 2 (CO) n species were readily synthesized at very low temperatures. ,− Multinuclear Cu n CO clusters with n = 1–4 were formed via the interaction of CO with small copper clusters and were identified spectroscopically in solid noble gas at cryogenic temperatures . The reactivity of copper cluster cations, neutrals, and anions with CO has been studied in the gas phase, and the dissociation energies of small anionic copper clusters monocarbonyls (Cu n CO – , n = 3–7) were measured via the threshold collision-induced dissociation method. − The bonding of carbon monoxide to small copper clusters was theoretically studied. − Density functional theory calculations indicate that the optimal unsaturated Cu 2 (CO) n ( n = 1–6) structures are generated by joining 18-electron tetrahedral, 16-electron trigonal, 14-electron linear copper carbonyl building blocks, and/or bare copper atoms with copper–copper single bonds rather than by joining 18-electron copper carbonyl units with multiple copper–copper bonds …”

Low-Energy Vibrations of the Group 10 Metal Monocarbonyl MCO (M = Ni, Pd, and Pt): Rotational Spectroscopy and Force Field Analysis

“…Historically, the group 10 metal monocarbonyls, MCO (M = Ni, Pd, and Pt), have been extensively studied by theoretical calculations, because such metals belong to an especially well exploited group of metals in heterogeneous and homogeneous catalytic systems. Lots of ab initio calculations ,− predicted that the group 10 metal monocarbonyls have 1 ∑ + electronic ground states. In contrast, experimental evidence for the group 10 metal monocarbonyls is sparse, and matrix-isolation infrared spectroscopy has been the only method for studying MCO experimentally. ,,,− This method has been mainly applied to the study of the ν 1 C−O stretching band (around 2000 cm −1 ) to investigate the π-back-donation contribution to the M−C bond.…”