The nature of the chemical bonding in 5d transition-metal diatomic borides MB (M = Ir, Pt, Au)
The nature of the chemical bonding in 5d transition-metal diatomic borides MB (M = Ir, Pt, Au)
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DOI：
10.1063/5.0008484
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发表时间：
2020-05-07
影响因子：
4.4
通讯作者：
Wang, Lai-Sheng
中科院分区：
文献类型：
--
作者：
Cheung, Ling Fung;Kocheril, G. Stephen;Wang, Lai-Sheng
在双原子金属硼化物（MB）中，硼可以与过渡金属形成强键，但化学键的性质尚未得到很好的理解。最近，在Rh中发现了四重键。B，由Rh 4d（z）（2）和B 2s/2 p轨道之间形成的两个σ键和Rh 4d（xz）/4d（yz）和B 2 p（x）/2 p（y）轨道之间的两个π键组成。预计5d过渡金属和硼之间的键合甚至更强。在这里，我们报告的电子结构和化学键的5d过渡金属双原子硼化物（IrB，PtB，和AuB）使用相应的阴离子（MB-）的高分辨率光电子成像和理论计算的调查。获得了所有三种阴离子的振动分辨光电子能谱，并且测量了IrB、PtB和AuB的电子亲合势分别为1.995（1）、2.153（3）和0.877（6）eV。结果表明，Ir B（（3）Delta）和Pt B（（2）Sigma（+））的弱反键3 σ分子轨道（主要是M6s和B sp特征）被单独占据，导致这两种双原子硼化物的键级为3.5。AuB（（1）Sigma（+））中的3 σ轨道被双重占据，产生弱三键。尽管Ir B和Pt B的键级较低，但由于M 5d轨道与B sp轨道之间的相互作用较好，它们的成键强度仅略弱于Rh B.由AIP Publishing授权出版。
Boron can form strong bonds with transition metals in diatomic metal borides (MB), but the nature of the chemical bonding has not been well understood. Recently, a quadruple bond was discovered in Rh?B, consisting of two sigma bonds formed between the Rh 4d(z)(2) and B 2s/2p orbitals and two pi bonds between the Rh 4d(xz)/4d(yz) and the B 2p(x)/2p(y) orbitals. The bonding between the 5d transition metals and boron is expected to be even stronger. Here, we report an investigation on the electronic structure and chemical bonding of the 5d transition metal diatomic borides (IrB, PtB, and AuB) using high-resolution photoelectron imaging on the corresponding anions (MB-) and theoretical calculations. Vibrationally resolved photoelectron spectra are obtained for all three anions, and the electron affinities are measured for IrB, PtB, and AuB to be 1.995(1), 2.153(3), and 0.877(6) eV, respectively. It is found that the weakly anti-bonding 3 sigma molecular orbital (mainly of M 6s and B sp characters) is singly occupied in IrB ((3)Delta) and PtB ((2)Sigma(+)), resulting in a bond order of three and half for these two diatomic borides. The 3 sigma orbital is doubly occupied in AuB ((1)Sigma(+)), giving rise to a weak triple bond. Despite the lower bond order, the bonding in IrB and PtB is only slightly weaker than that in RhB due to the more favorable interactions between the M 5d orbitals and the B sp orbitals. Published under license by AIP Publishing.