N-heterocyclic carbone: computational prediction of a divalent carbon (0) compound

Figures & data

Figure 1 Schematic representation of carbodicarbene, (1) C(NHC)₂ and (2) CDP.

Abbreviations: NHC, N-heterocyclic carbene; CDP, carbodiphosphoranes.

Figure 2 Schematic representation of bis(imidazolin-2-iminium) cation (A) and the boron cation compound (B).

Figure 3 Donor–acceptor interaction in B.

Figure 4 Optimized geometries at BP86/TZVP level of theory and relative energies (kcal/mol at MP2/aug-cc-pVDZ//BP86/TZVP) of different conformers of 3H.

Notes: Bond lengths are in Å and angles are in degrees. Number of imaginary frequencies (i) is also provided.

Figure 5 Shape of frontier Kohn–Sham orbitals of 3H and orbital energies ε in eV at the BP86/TZVP level of theory.

Abbreviation: HOMO, highest occupied molecular orbital.

Figure 6 BP86/TZVP optimized first and second protonated derivatives of 3H.

Table 1 MP2/aug-cc-pVDZ//BP86/TZVP calculated proton affinities (in gas phase); PAs (kcal/mol) of 1–3

Molecule	PA1	PA2
1H	283.2 (292.3)	151.2 (155.3)
2Me	278.3 (278.4)	158.9 (156.2)
3H	287.5	192.1

Note: Data from Tonner R, Frenking G. C(NHC)2: divalent carbon(0) compounds with N-heterocyclic carbene ligands-theoretical evidence for a class of molecules with promising chemical properties. Angew Chem Int Ed Engl. 2007;46:8695.¹

Abbreviation: PA, proton affinity.

Figure 7 BP86/BSI (BSI = TZVP for H, C, N, Cl and SDD for Au) optimized protonated derivatives of 3H.

Note: The Au–Au distance in 3H-(AuCl)₂ is 3.351 Å, which is longer than the typical Au–Au distance of ~3.0 Å. Data from Schmidbaur H. The aurophilicity phenomenon: a decade of experimental findings, theoretical concepts and emerging applications. Gold Bull. 2000;33:3.⁵⁰
Abbreviation: SDD, Stuttgart/Dresden.

Table 2 Calculated reaction Gibbs free energies (kcal/mol) of reactions 1 and 2 at T=298.15 K and P=1 atm

Reaction	∆G
	BP86		B3LYP		B3PW91
	Gas	Solution	Gas	Solution	Gas	Solution
1	−194.6	−14.7	−192.3	−15.2	−188.4	−13.6
2	−232.4	−11.6	−229.5	−12.4	−224.2	−10.8

Note: Values are zero-point corrected.

Schmidbaur H. The aurophilicity phenomenon: a decade of experimental findings, theoretical concepts and emerging applications. Gold Bull. 2000;33:3.

 Web of Science ®Google Scholar