Isolation of Neutral, Mono-, and Dicationic B
2 P
2 Rings by Diphosphorus Addition to a Boron-Boron Triple Bond.
Angew Chem Int Ed Engl 2021;
60:13661-13665. [PMID:
33844394 PMCID:
PMC8252364 DOI:
10.1002/anie.202102218]
[Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 04/09/2021] [Indexed: 01/10/2023]
Abstract
The NHC-stabilised diboryne (B2 (SIDep)2 ; SIDep=1,3-bis(2,6-diethylphenyl)imidazolin-2-ylidene) undergoes a high-yielding P-P bond activation with tetraethyldiphosphine at room temperature to form a B2 P2 heterocycle via a diphosphoryldiborene by 1,2-diphosphination. The heterocycle can be oxidised to a radical cation and a dication, respectively, depending on the oxidant used and its counterion. Starting from the planar, neutral 1,3-bis(alkylidene)-1,3-diborata-2,4-diphosphoniocyclobutane, each oxidation step leads to decreased B-B distances and loss of planarity by cationisation. X-ray analyses in conjunction with DFT and CASSCF/NEVPT2 calculations reveal closed-shell singlet, butterfly-shaped structures for the NHC-stabilised dicationic B2 P2 rings, with their diradicaloid, planar-ring isomers lying close in energy.
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