Bonding analysis of ylidone complexes EL2 (E = C–Pb) with phosphine and carbene ligands L

2016 ◽  
Vol 94 (12) ◽  
pp. 1006-1014 ◽  
Author(s):  
Diego M. Andrada ◽  
Nicole Holzmann ◽  
Gernot Frenking
Keyword(s):  
Quantum Chemical ◽  
Lone Pair ◽  
Linear Structure ◽  
Decomposition Methods ◽  
Energy Decomposition ◽  
Proton Affinities ◽  
Carbene Ligands ◽  
Lewis Bases ◽  
Bonding Analysis ◽  
Equilibrium Structures

Quantum chemical calculations using DFT and ab initio methods have been carried out of the compounds EL2 with atoms E = C–Pb and the ligands L = PPh3, N-heterocyclic carbene (NHC), bicyclic NHC, and cyclic alkyl-amino carbene (cAAC). The equilibrium structures are reported and the bonding situation was analyzed with a variety of charge- and energy decomposition methods. Some of the molecules are experimentally known, but most molecules have not yet been prepared. The bonding analysis suggests that all but one molecule should be considered as ylidones that possess dative bonds L→E←L. The sole exception is C(cAAC)2, which has a linear structure and classical double bonds (cAAC)=C=(cAAC). The ylidones EL2 have two lone-pair orbitals at atom E with σ and π symmetry. The π lone pair is somewhat delocalized due to L←E→L π-backdonation. The contribution of L←E→L π-backdonation relative to L→E←L σ-donation increases for the heavier elements. The compounds have rather large first and second proton affinities, which is a characteristic feature of ylidones. They are thus double Lewis bases that could be utilized in chemical reactions.

scholarly journals Structures, Energies, and Bonding Analysis of Monoaurated Complexes with N-Heterocyclic Carbene and Analogues

2017 ◽  
Vol 32 (1) ◽  
pp. 1 ◽  
Author(s):  
T.A.N. NGUYEN ◽  
T.P.L. HUYNH ◽  
T.X.P. VO ◽  
T.H. TRAN ◽  
D.S. TRAN ◽  
...  
Keyword(s):  
Lone Pair ◽  
Decomposition Methods ◽  
Basis Sets ◽  
Bonding Analysis ◽  
Donor Acceptor ◽  
Equilibrium Structures ◽  
Lone Pair Electrons ◽  
Back Donation ◽  
Ligand Bond ◽  
Vacant Orbital

In this work, we computationally investigated from quantum chemical calculations (DFT) at the BP86 level with the various basis sets def2-SVP, def2-TZVPP, and TZ2P+, chemical bonding issues of the recently described carbene-analogues gold(I) complexes AuCl-NHEMe (Au1-NHE) with E = C – Pb. The optimized structures and the metal-ligand bond dissociation energy (BDE) were calculated, and the nature of the E→Au bond was studied with charge and energy decomposition methods. The equilibrium structures of the system showed that there were major differences in the bonded orientation from the ligands NHC-NHPb to gold(I) complex between the lighter and the heavier homologues. The BDEs results showed that the metal-carbene analogues bonds were very strong bonds and the strongest bond was calculated for Au1-NHC which had the bond strength De = 79.2 kcal/mol. Bonding analysis of Au1-NHE showed that NHE ligands exhibited donor-acceptor bonds with the σ lone pair electrons of NHE donated into the vacant orbital of the acceptor fragment (AuCl). The EDA-NOCV results indicated that the ligand NHE in Au1-NHE complexes were strong σ-donors and very weak π donor and the bond order in complexes was Au1-NHC > Au1-NHSi > Au1-NHGe > Au1-NHSn > Au1-NHPb. We also realised that the gold-ligand bond was characterized by a π back-donation component from the Au to the ligand. All investigated complexes in this study were suitable targets for synthesis and gave a challenge in designing Au nano-crystals of narrow size distribution from gold(I) complexes that carried versatile N-heterocyclic carbene-analogues NHE.

scholarly journals Quantum chemical investigation for structures and bonding analysis of molybdenum tetracarbonyl complexes with N-heterocyclic carbene and analogues: helpful information for plant biology research

2014 ◽  
Vol 6 (2) ◽  
pp. 142-148
Author(s):  
Thi Ai Nhung Nguyen ◽  
Thi Phuong Loan Huynh ◽  
Van Tat Pham
Keyword(s):  
Quantum Chemical ◽  
Density Functional ◽  
Energy Levels ◽  
Plant Biology ◽  
Basis Sets ◽  
Equatorial Position ◽  
Strong Electron ◽  
Bonding Analysis ◽  
Equilibrium Structures ◽  
Biology Research

Quantum chemical calculations at the gradient-corrected (BP86) density-functional calculations with various basis sets (SVP, TZVPP) have been carried out for Mo(CO)4 complexes of N-heterocyclic carbene and analogues-NHEMe (called tetrylenes) with E = C, Si, Ge, Sn, Pb. The equilibrium structures of complexes [Mo(CO)4-NHEMe] (Mo4-NHEMe) exhibit an interesting trend which the lightest adduct Mo4-NHCMe has a trigonal bipyramidal coordination mode where the ligand NHCMe occupies an equatorial position. In contrast, the heavier species from Mo4-NHSiMe to Mo4-NHPbMe possess a square pyramidal structure where the ligands from NHSiMe to NHPbMe occupy a basal position. The slighter complexes Mo4-NHEMe possess end-on-bonded NHEMe ligands when E = C, Si, Ge with the bending angles, , are 180° whereas the heavier adducts Mo4-NHSnMe and Mo4-NHPbMe exhibit strongly side-on-bonded ligands which the bending angle,  become more acute. The trend of the bond dissociations energies-De [kcal/mol] (BDEs) for the Mo-E bonds is Mo4-NHCMe > Mo4-NHSiMe > Mo4-NHGeMe > Mo4-NHSnMe > Mo4-NHPbMe. Bonding analysis shows that the Mo-E bonds have a significant contribution from (CO)4Mo ← NHEMe π-donation. This is because the energy levels of the π-type donor orbitals of Mo4-NHCMe − Mo4-NHPbMe are higher lying than the σ-type donor orbitals. The NHEMe ligands in Mo4-NHEMe are strong electron donors. This review intends to provide a comprehensive data for plant biology research in the future. Tính toán hóa lượng tử sử dụng lý thuyết phiếm hàm mật độ kết hợp điều chỉnh gradient (BP86) từ các bộ hàm cơ sở khác nhau (SVP, TZVPP) được thực hiện cho việc tính toán lý thuyết của phức giữa Mo(CO)4 và phối tử N-heterocyclic carbene và các phức tương tự NHEMe (gọi là tetrylenes) với E = C, Si, Ge, Sn, Pb. Cấu trúc của phức [Mo(CO)4-NHEMe] (Mo4-NHEMe) thể hiện sự khác biệt khá thú vị từ Mo4-NHCMe đến Mo4-NHPbMe, phức Mo4-NHCMe có cấu trúc phối trí lưỡng tháp tam giác trong đó phối tử NHCMe chiếm ở vị trí xích đạo. Ngược lại, những phức có phân tử khối lớn hơn từ Mo4-NHSiMe đến Mo4-NHPbMe lại có cấu trúc tháp vuông và các phối tử từ NHSiMe đến NHPbMe chiếm vị trí cạnh (basal – cạnh hướng về bốn đỉnh của đáy vuông). Các cấu trúc của phức Mo4-NHEMe cho thấy các phối tử NHEMe với E = C-Ge tạo với phân tử Mo(CO)4 một góc thẳng =180.0°, ngược lại, các phức nặng hơn Mo4-NHEMe thì phối tử NHEMe với E = Sn, Pb liên kết với phân tử Mo(CO)4 tạo góc cong và góc cong, , càng trở nên nhọn hơn khi nguyên tử khối của E càng lớn. Năng lượng phân ly liên kết của liên kết Mo-E giảm dần: Mo4-NHCMe > Mo4-NHSiMe > Mo4-NHGeMe > Mo4-NHSnMe > Mo4-NHPbMe. Phân tích liên kết Mo-E cho thấy có sự đóng góp đáng kể của sự cho liên kết π (CO)4Mo ← NHEMe. Điều này có thể do mức năng lượng của orbital π-cho của Mo4-NHCMe − Mo4-NHPbMe nằm cao hơn orbital σ-cho. Từ kết quả tính toán có thể kết luận rằng phối tử NHEMe trong phức Mo4-NHEMe là chất cho điện tử mạnh. Kết quả nghiên cứu lý thuyết về hệ phức Mo4-NHEMe lần đầu tiên cung cấp một cơ sở dữ liệu hoàn chỉnh cho các nghiên cứu về sinh học thực vật trong tương lai.

scholarly journals Direct estimate of the internal π-donation to the carbene centre within N-heterocyclic carbenes and related molecules

2015 ◽  
Vol 11 ◽  
pp. 2727-2736 ◽  
Author(s):  
Diego M Andrada ◽  
Nicole Holzmann ◽  
Thomas Hamadi ◽  
Gernot Frenking
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Decomposition Analysis ◽  
Heterocyclic Carbenes ◽  
Energy Decomposition Analysis ◽  
Energy Decomposition ◽  
Direct Estimate ◽  
Functional Theory ◽  
Bonding Analysis

Fifteen cyclic and acylic carbenes have been calculated with density functional theory at the BP86/def2-TZVPP level. The strength of the internal X→p(π) π-donation of heteroatoms and carbon which are bonded to the C(II) atom is estimated with the help of NBO calculations and with an energy decomposition analysis. The investigated molecules include N-heterocyclic carbenes (NHCs), the cyclic alkyl(amino)carbene (cAAC), mesoionic carbenes and ylide-stabilized carbenes. The bonding analysis suggests that the carbene centre in cAAC and in diamidocarbene have the weakest X→p(π) π-donation while mesoionic carbenes possess the strongest π-donation.

scholarly journals A G2(MP2) theoretical study of substituent effects on H3BNHnCl3−n (n= 3-0) donor-acceptor complexes

2008 ◽  
Vol 6 (3) ◽  
pp. 400-403 ◽  
Author(s):  
Hafid Anane ◽  
Soufiane Houssame ◽  
Abdelali Guerraze ◽  
Abdeladim Guermoune ◽  
Abderrahim Boutalib ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Substituent Effects ◽  
Lone Pair ◽  
Proton Affinities ◽  
Lone Pair Orbital ◽  
Chlorine Substitution ◽  
Donor Acceptor ◽  
Nitrogen Lone Pair ◽  
The Stability ◽  
N Compounds

AbstractThe complexation energies of H3BNHnCl3−n (n= 3-0) complexes and the proton affinities of NHnCl3−n compounds have been computed at the G2(MP2) level of theory. G2(MP2) results show that the successive chlorine substitution on the ammonia decreases both the basicity of the NHnCl3−n ligands and the stability of H3BNHnCl3−n complexes. The findings are interpreted in terms of the rehybridisation of the nitrogen lone-pair orbital. The NBO partitioning scheme shows that the variation of the N-H and N-Cl bond lengths, upon complexation, is due to variation of “s” character in these bonds.

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