D4h Ni4C(B4N4H8)2: Square sheet sandwich complex containing the planar tetracoordinate carbon

Abstract

The investigation on the geometrical and electronic properties of the novel square sheet sandwich complex D4h Ni4C(B4N4H8)2 containing the planar tetracoordinate carbon has been performed by density functional theory (DFT) using the B3LYP and PBE1PBE methods at the 6-311+G(d,p) level. Singlet D4h Ni4C(B4N4H8)2 is the true minimum with real frequencies and lower energy than its triplet, quintuplet, septet structures. Different from the previously reported D4h Ni4C(C8H8)2, the Ni4C2+ deck was sandwiched by two B4N4H8− ligands with the μ4-η1:η1:η1:η1(–N) coordination mode in D4h Ni4C(B4N4H8)2. The effective d–p coordination interactions between the Ni atoms and the π orbitals of the B4N4H8− ligands, the Ni–Ni and Ni–ptC covalent interactions cooperate to maintain the stability of the sandwich complex. The negative NICSzz(1) clearly indicated the ligands B4N4H8− in D4h Ni4C(B4N4H8)2 is aromatic. The negative energy change −83.53kcal/mol indicates that the insertion of a ptC atom in the center of Ni4(B4N4H8)2 to form Ni4C(B4N4H8)2 complex is favored thermodynamically. To facilitate the future experiment, the infrared (IR) spectrums of D4h Ni4C(B4N4H8)2 and Ni4C(B4N4H8)2 complexes have been simulated. The novel square sheet sandwich complex thermodynamically turn out to be stable and may be synthesized in future experiments to expand the domain of ptC complexes.