Computational Investigation of Carbene–Phosphinidenes: Correlation between ³¹P Chemical Shifts and Bonding Features to Estimate the π-Backdonation of Carbenes

Abstract

Detailed investigations of the electronic structure and bonding scenario in different carbene-phosphinidenes have been presented using state-of-the-art computational methods (BP86/def2-TZVPP//BP86/def2-SVP). We have endeavored to find the correlation of the calculated P chemical shifts with different bonding parameters of compounds to access the relative π-acceptor strengths of the carbenes.P chemical shifts exhibit a weak correlation with σ-polarizations of C-P bonds toward phosphorus; however excellent correlations are obtained in the case of π-polarizations of C-P bonds toward the carbene carbon (C) and NPA charges on phosphorus atoms. P chemical shifts also show excellent correlations with the electron densities and energy densities of C-P bonds at BCPs, as suggested by QTAIM calculations. Moreover, EDA-NOCV analysis is implemented to gain brief insight into the bonding scenario in this class of compounds. Good correlation exists between the interaction energies between the carbene and PPh fragments and P chemical shifts. Additionally, we have investigated the correlations of calculatedP chemical shifts with different bonding parameters of the corresponding free carbenes. The bonding scenario in different carbene-substituted phosphinidenes is also explored to see how the bonding situation depends on various substituents on phosphinidenes. The other substituted carbene-phosphinidenes show correlations similar to those of carbene-phenylphosphinidenes.

How to Bend a Cumulene

“…Other carbenes that have been used in the synthesis of carbones are CAACs. These ligands are stronger π acceptors than NHCs . Moreover, the syntheses of [3]cumulenes with CAACs as terminal groups have been successful, contrary to NHCs .…”

“…These ligands are stronger p acceptors than NHCs. [48][49][50][51] Moreover,t he syntheses of [3]cumulenes with CAACsa st erminal groups have been successful, [39,40] contrary to NHCs. [30,38] TheP ESs of CAAC [2n]cumulenes are also shallower than those of the odd cumulenes, but the two sets are more similart han in the case of the NHC cumulenes (Figure 2b).…”

Computational Ligand Descriptors for Catalyst Design

“…Frenking's group have made a considerable contribution in this area, [168][169][170][171] using energy and charge partitioning approaches to assess the bonding in a wide range of transition metal-carbene complexes. By comparing calculated structural parameters with quantitative measures of backbonding, 169 their work has helped to lay the foundations for other analyses (see for example references 142,143,153,158,172,173); we note that other approaches to the analysis of backbonding have also been reported. 174 When initially reported, such calculations tended to be focussed on comparing carbenes with each other, but some of these descriptors have found their way into catalytic applications more recently and so merit inclusion here.…”

Modeling ligand electrochemical parameters by repulsion‐corrected eigenvalues

“…[10][11][12][13][14][15] These are but a few of the cases where E L parameters have been utilized in leading scientific fields. [16][17][18][19][20][21][22][23][24][25][26][27] Although originally parameterized for octahedral complexes, E L parameters are also reliable predictors of redox potentials of four 28 and five 29 coordinate species, macrocycles 30 and sandwich organometallics. 31 Although empirically well characterized, Lever parameters have not been well understood at a theoretical level, although it has long been recognized that highly π-accepting ligands tend to electrons of Ru should be primarily influenced by ligand π-effects,…”