Formation and Characterization of a BeOBeC Multiple Radical Featuring a Quartet Carbyne Moiety

Abstract

Through reaction of beryllium dimers with carbon monoxide, a carbonyl complex BeBeCO is formed in solid neon. Upon visible light excitation, the BeBeCO complex rearranges to a BeCOBe isomer, which further isomerizes to a low‐energy BeOBeC species under UV‐visible light excitation. These species are identified on the basis of infrared absorption spectroscopy with isotopic substitutions and quantum chemical studies. The BeOBeC molecule is characterized to be a multiple radical species having an electronic quintet ground state featuring an unusual quartet carbyne unit with three unpaired electrons on the carbon center. Bonding analysis indicates that the strong Pauli repulsion between carbon 2s lone pair electrons and the σ electrons of the BeOBe fragment significantly weakens the Be−C bonding and destabilizes the triplet state of the BeOBeC radical with a doublet carbyne unit. The three‐center π‐bonding of BeOBe is also found to play a role in stabilizing the quartet carbyne.

Beryllium Atom Mediated Dinitrogen Activation via Coupling with Carbon Monoxide

“…Three absorptions were observed for species B, which is assigned to the (h 2 -N 2 )BeCO isomer involving an end-on bonded carbonyl ligand and a side-on bonded N 2 ligand. The 1988.3 cm À1 band shows quite small 15 N isotopic shift (À4.4 cm À1 ) but quite large 13 C (À41.4 cm À1 ) and 18 O (À37.0 cm À1 ) isotopic shifts (Table 1), and thus, is assigned to the carbonyl stretching vibration. The doublet isotopic structures in the mixed 12 CO + 13 CO/N 2 and C 16 O + C 18 O/N 2 experiments ( Figure S1, spectra b and c) confirm that only one CO fragment is involved in this mode.…”

Revisiting the Intriguing Electronic Features of the BeOBeC Carbyne and Some Isomers: A Quantum‐Chemical Assessment

“…Electronic Configuration A comparison of the experimentally obtained with the calculated IR spectrum of the linear BeOBeC isomer in its 5 S state revealed a good agreement. [17] The presence of a spin isomer, for instance the 3 S species ( 3 6) in which the unpaired electron at the terminal beryllium atom is antiferromagnetically coupled to one of the unpaired electrons at the carbon unit, was not discussed in the previous publication. [17] As shown in Table 1, extensive CCSD(T) calculations (for computational details, see the Supporting Information) reveal that both the triplet and quintet of BeOBeC ( 3,5 6) are almost isoenergetic at 4 K, with a tiny energetic preference for 5 6.…”

A Homoleptic Beryllium Carbonyl Complex with an End‐On and Side‐On Bridging Carbonyl Ligand

“…The other coordination modes that are quite common in transition‐metal carbonyl complexes are rarely observed in the main‐group element carbonyl complexes. Only very few dinuclear Group 13 metal carbonyl complexes were reported to involve the end‐on bridging carbonyl ligands, [20] and a high‐lying BeCOBe species has been characterized to involve a linear bridging CO unit [21] . Herein we report the generation and infrared spectroscopic detection of a homoleptic beryllium carbonyl cation complex Be 2 (CO) 5 + and its weakly bound CO‐tagged Be 2 (CO) 6 + complex in the gas phase, which are characterized to coexist two almost isoenergetic structural isomers.…”