Substituent Effect Parameters: Extending the Applications to Organometallic Chemistry

Abstract

Typically, metal complexes are constituted of an acceptor metal ion and one or more Iigands containing the donor atoms. Accordingly, the properties of a metal complex are equally dependent on the nature of the metal ion and the ligands. Minute structural variations in the ligand will may result in linear changes in the respective energetic parameters and such linear relationships have paramount importance in organometallic chemistry. The variation in ligands is virtually limitless and substantial because of the extent of organic chemistry available for the modelling of desirable ligands, apart from the variation in metal ions. Anyhow, there is still a need for new parameters for the design and quantification of new ligands which in turn leads to the synthesis of metal complexes with possibly predictable chemical properties. Previous studies have demonstrated that quantum chemically derived molecular electrostatic potential (MESP) parameters can be listed as one of the superior quantifiers in this regard, which can act as an effective ligand electronic parameter. The interaction between the ligand part and metal-containing part will be crucial in assessing the reactivity of organometallic complexes. Here we are applying MESP based substituent constants derived from substituted benzenes to forecast the interaction energies in (pyr*)W(CO) 5 , (NHC*)Mo(CO) 5 and (η 6 -arene*)Cr(CO) 3 complexes. Ligands and metal ions are varied in each case for better understanding and transparency.[a] G.

Molecular electrostatic potential analysis: A powerful tool to interpret and predict chemical reactivity

“…Recently, the electron-rich/deficient character of lone-pair bearing nitrogen (V N ) centers in substituted 1, 10-phenanthroline (phen*) systems and their coordination ability with Mo(CO) 4 were quantified using MESP parameters. 171,172 The MESP-based substituent parameter (ΔV C ) deduced for benzene systems showed transferability property to the metal complex and it was used to predict reactivity patterns of various metal carbonyls. The electron donation from the phenanthroline ligands to the metal center led to increased negative character for MESP at CO ligands which decreased the CO stretching frequency.…”

Adsorption of Gases on Fullerene-like X12Y12 (X = Be, Mg, Ca, B, Al, Ga, C; Y = C, Si, N, P, O) Nanocages

“…NO is found to be strongly adsorbed on B 12 P 12 , Be 12 O 12 , Ca 12 O 12 , and C 24 , and CO is strongly adsorbed on B 12 N 12 , B 12 P 12 , Be 12 O 12 , and C 24 . The deepest molecular electrostatic potential (MESP) minimum, V min , indicates the electron-rich sites such as lone pairs and π-bonds of the molecules. − An interesting finding is that the V min values of the X 12 Y 12 nanocages are linearly proportional to their CO 2 or NO adsorption energies. The insights from this work will further assist in the design and development of efficient materials for gas capture and storage applications.…”

Molecular electrostatic potential as a general and versatile indicator for electronic substituent effects: statistical analysis and applications

“…11,12 Further research was conducted to establish a strong linear correlation between the Hammett (and other related) parameters and the electrostatic potentials at the critical points of substituted aromatic rings, [13][14][15][16] reaction sites, 17 or the centres of the specific atoms, including the nitrogen atoms from amine groups 16,18 or carbon atoms on aromatic rings. 19 Furthermore, it was reported that MESP can be applied to linear regression with calculated electronic properties such as Tolman electronic parameter, 20,21 the interaction energy between transition metal complex and chelate, 21 and that between cation and substituted p-conjugated ring. 22 The usage of MESP is not limited to the ground state of molecule.…”