TY - JOUR
T1 - Borylene complexes (BH)L 2 and nitrogen cation complexes (N +)L 2
T2 - Isoelectronic homologues of carbones CL 2
AU - Celik, Mehmet Ali
AU - Sure, Rebecca
AU - Klein, Susanne
AU - Kinjo, Rei
AU - Bertrand, Guy
AU - Frenking, Gernot
PY - 2012/4/27
Y1 - 2012/4/27
N2 - Quantum chemical calculations using DFT (BP86, M05-2X) and ab initio methods (CCSD(T), SCS-MP2) have been carried out on the borylene complexes (BH)L 2 and nitrogen cation complexes (N +)L 2 with the ligands L=CO, N 2, PPh 3, NHC Me, CAAC, and CAAC model. The results are compared with those obtained for the isoelectronic carbones CL 2. The geometries and bond dissociation energies of the ligands, the proton affinities, and adducts with the Lewis acids BH 3 and AuCl were calculated. The nature of the bonding has been analyzed with charge and energy partitioning methods. The calculated borylene complexes (BH)L 2 have trigonal planar coordinated boron atoms which possess rather short B-L bonds. The calculated bond dissociation energies (BDEs) of the ligands for complexes where L is a carbene (NHC or CAAC) are very large (D e=141.6-177.3 kcalmol -1) which suggest that such species might become isolated in a condensed phase. The borylene complexes (BH)(PPh 3) 2 and (BH)(CO) 2 have intermediate bond strengths (D e=90.1 and 92.6 kcalmol -1). Substituted homologues with bulky groups at boron which protect the boron atom from electrophilic attack might also be stable enough to become isolated. The BDE of (BH)(N 2) 2 is much smaller (D e=31.9 kcalmol -1), but could become observable in a low-temperature matrix. The proton affinities of the borylene complexes are very large, particularly for the bulky adducts with L=PPh 3, NHC Me, CAAC model and CAAC and thus, they are superbases. All (BH)L 2 molecules bind strongly AuCl either I· 1 (L=N 2, PPh 3, NHC Me, CAAC) or I· 2 (L=CO, CAAC model). The BDEs of H 3B-(BH)L 2 adducts which possess a hitherto unknown boron→boron donor-acceptor bond are smaller than for the AuCl complexes. The strongest bonded BH 3 adduct that might be isolable is (BH)(PPh 3) 2-BH 3 (D e=36.2 kcalmol -1). The analysis of the bonding situation reveals that (BH)-L 2 bonding comes mainly from the orbital interactions which has three major contributions, that is, the donation from the symmetric (Ï) and antisymmetric (π ||) combination of the ligand lone-pair orbitals into the vacant MOs of BH L→(BH)←L and the L←(BH)→L π backdonation from the boron lone-pair orbital. The nitrogen cation complexes (N +)L 2 have strongly bent L-N-L geometries, in which the calculated bending angle varies between 113.9° (L=N 2) and 146.9° (L=CAAC). The BDEs for (N +)L 2 are much larger than those of the borylene complexes. The carbene ligands NHC and CAAC but also the phosphane ligands PPh 3 bind very strongly between D e=358.4 kcalmol -1 (L=PPh 3) and D e=412.5 kcalmol -1 (L=CAAC model). The proton affinities (PA) of (N +)L 2 are much smaller and they bind AuCl and BH 3 less strongly compared with (BH)L 2. However, the PAs (N +)L 2 for complexes with bulky ligands L are still between 139.9 kcalmol -1 (L=CAAC model) and 168.5 kcalmol -1 (L=CAAC). The analysis of the (N +)-L 2 bonding situation reveals that the binding interactions come mainly from the L→(N +)←L donation while L←(N +)→L π backdonation is rather weak.
AB - Quantum chemical calculations using DFT (BP86, M05-2X) and ab initio methods (CCSD(T), SCS-MP2) have been carried out on the borylene complexes (BH)L 2 and nitrogen cation complexes (N +)L 2 with the ligands L=CO, N 2, PPh 3, NHC Me, CAAC, and CAAC model. The results are compared with those obtained for the isoelectronic carbones CL 2. The geometries and bond dissociation energies of the ligands, the proton affinities, and adducts with the Lewis acids BH 3 and AuCl were calculated. The nature of the bonding has been analyzed with charge and energy partitioning methods. The calculated borylene complexes (BH)L 2 have trigonal planar coordinated boron atoms which possess rather short B-L bonds. The calculated bond dissociation energies (BDEs) of the ligands for complexes where L is a carbene (NHC or CAAC) are very large (D e=141.6-177.3 kcalmol -1) which suggest that such species might become isolated in a condensed phase. The borylene complexes (BH)(PPh 3) 2 and (BH)(CO) 2 have intermediate bond strengths (D e=90.1 and 92.6 kcalmol -1). Substituted homologues with bulky groups at boron which protect the boron atom from electrophilic attack might also be stable enough to become isolated. The BDE of (BH)(N 2) 2 is much smaller (D e=31.9 kcalmol -1), but could become observable in a low-temperature matrix. The proton affinities of the borylene complexes are very large, particularly for the bulky adducts with L=PPh 3, NHC Me, CAAC model and CAAC and thus, they are superbases. All (BH)L 2 molecules bind strongly AuCl either I· 1 (L=N 2, PPh 3, NHC Me, CAAC) or I· 2 (L=CO, CAAC model). The BDEs of H 3B-(BH)L 2 adducts which possess a hitherto unknown boron→boron donor-acceptor bond are smaller than for the AuCl complexes. The strongest bonded BH 3 adduct that might be isolable is (BH)(PPh 3) 2-BH 3 (D e=36.2 kcalmol -1). The analysis of the bonding situation reveals that (BH)-L 2 bonding comes mainly from the orbital interactions which has three major contributions, that is, the donation from the symmetric (Ï) and antisymmetric (π ||) combination of the ligand lone-pair orbitals into the vacant MOs of BH L→(BH)←L and the L←(BH)→L π backdonation from the boron lone-pair orbital. The nitrogen cation complexes (N +)L 2 have strongly bent L-N-L geometries, in which the calculated bending angle varies between 113.9° (L=N 2) and 146.9° (L=CAAC). The BDEs for (N +)L 2 are much larger than those of the borylene complexes. The carbene ligands NHC and CAAC but also the phosphane ligands PPh 3 bind very strongly between D e=358.4 kcalmol -1 (L=PPh 3) and D e=412.5 kcalmol -1 (L=CAAC model). The proton affinities (PA) of (N +)L 2 are much smaller and they bind AuCl and BH 3 less strongly compared with (BH)L 2. However, the PAs (N +)L 2 for complexes with bulky ligands L are still between 139.9 kcalmol -1 (L=CAAC model) and 168.5 kcalmol -1 (L=CAAC). The analysis of the (N +)-L 2 bonding situation reveals that the binding interactions come mainly from the L→(N +)←L donation while L←(N +)→L π backdonation is rather weak.
KW - bonding analysis
KW - carbones
KW - donor-acceptor systems
KW - nitrogen cation complexes
KW - quantum chemistry
UR - http://www.scopus.com/inward/record.url?scp=84859974007&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84859974007&partnerID=8YFLogxK
U2 - 10.1002/chem.201103965
DO - 10.1002/chem.201103965
M3 - Article
AN - SCOPUS:84859974007
SN - 0947-6539
VL - 18
SP - 5676
EP - 5692
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 18
ER -