Heteroborospherene clusters Nin ∈ B40 (n = 1–4) and heteroborophene monolayers Ni2 ∈ B14 with planar heptacoordinate transition-metal centers in η7-B7 heptagons

• Published in: Scientific reports 2017-07, Vol.7 (1), p.1-7, Article 5701
• Main Authors: Li, Hai-Ru, Tian, Xin-Xin, Luo, Xue-Mei, Yan, Miao, Mu, Yue-Wen, Lu, Hai-Gang, Li, Si-Dian
• Format: Article
• Language: English
• Subjects: 119/118; 639/301; 639/638; Boron; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-017-06039-9

With inspirations from recent discoveries of the cage-like borospherene B 40 and perfectly planar Co ∈ B 18 − and based on extensive global minimum searches and first-principles theory calculations, we present herein the possibility of the novel planar Ni ∈ B 18 (1), cage-like heteroborospherenes Ni n  ∈ B 40 (n = 1–4) (2–5), and planar heteroborophenes Ni 2  ∈ B 14 (6, 7) which all contain planar or quasi-planar heptacoordinate transition-metal (phTM) centers in η 7 -B 7 heptagons. The nearly degenerate Ni 2  ∈ B 14 (6) and Ni 2  ∈ B 14 (7) monolayers are predicted to be metallic in nature, with Ni 2  ∈ B 14 (6) composed of interwoven boron double chains with two phNi centers per unit cell being the precursor of cage-like Ni n  ∈ B 40 (n = 1–4) (2–5). Detailed bonding analyses indicate that Ni n  ∈ B 40 (n = 1–4) (2–5) and Ni 2  ∈ B 14 (6, 7) possess the universal bonding pattern of σ + π double delocalization on the boron frameworks, with each phNi forming three lone pairs in radial direction (3d z2 2 , 3d zx 2 , and 3d yz 2 ) and two effective nearly in-plane 8c-2e σ-coordination bonds between the remaining tangential Ni 3d orbitals (3d x2−y2 and 3d xy ) and the η 7 -B 7 heptagon around it. The IR, Raman, and UV-vis absorption spectra of 1–5 are computationally simulated to facilitate their experimental characterizations.