Optical spectroscopy of RuC: 18 000–24 000 cm−1

Quadruple chemical bonding in the diatomic anions TcN- , RuC- , RhB- , and PdBe. J Comput Chem 2021;42:1126-1137. [PMID: 33851470 DOI: 10.1002/jcc.26527]

Quadruple bonding is uncommon for main group elements and the identification of species forming such bonds is remarkably interesting particularly in diatomic anions for which there is a lack of information. Here, it is found that the MX^- anions, TcN^- , RuC^- , RhB^- , and PdBe^- , present quadruple bonding, as do the corresponding MX neutrals, even though a different type of σ² bond is involved in ∑⁺ states of neutral and anions. Specifically, the ground states (X² Δ or X² ∑⁺ ) of the four anions and their first excited states (A² ∑⁺ or A² Δ) of TcN^- , RuC^- , and RhB^- present quadruple bonds consisting of two σ and two π bonds: (4d_z2  - 2p_z )² , 5p_z ⁰  ← 2s² , (4d_xz  - 2p_x )² , and (4d_yz  - 2p_y )² . Bond lengths, dissociation energies, spectroscopic data and electron affinities were calculated via high-level multireference and coupled-cluster methodology using the aug-cc-pV5Z_X (-PP)_M basis set. Strong bonding results in short bond lengths ranging from 1.602 (TcN^- ) to 1.944 (PdBe^- ) Å. Adiabatic (diabatic) binding energies reach up to 139 (184) kcal/mol. Electron affinities (EA) were calculated at 1.368 (TcN), 1.242 (RuC), 0.873 (RhB), 0.743 (PdBe) eV. Only for RhB has EA been measured experimentally at 0.961 eV, in good agreement with the value reported here.

Rotationally resolved spectra of jet-cooled RuSi

We report the first gas-phase spectroscopic investigation of diatomic ruthenium silicide (RuSi). The molecules were produced by laser ablation of a Ru disk into a flow of helium carrier gas containing 0.5% SiH(4), and were cooled in a supersonic expansion. The RuSi molecules were then studied using resonant two-photon ionization spectroscopy. Investigations conducted in the spectral range from 18,800 to 23,800 cm(-1) show a large number of excited vibronic levels that cannot readily be grouped into electronic band systems. The ground state is been demonstrated to be of (3)Delta(3) symmetry, deriving from the 2delta(3)14sigma(1) electronic configuration. Correcting for the effects of the spin-uncoupling operator, the ground state bond length (r(0)) is determined to be 2.0921+/-0.0004 A (1sigma error limit). Diatomic RuSi is shown to have strong dpi-ppi bonds, unlike the isovalent AlCo molecule.