Isolation of Carbene-Stabilized Arsenic Monophosphide [AsP] and its Radical Cation [AsP] +. and Dication [AsP] 2 .

Arsenic monophosphide (AsP) species supported by two different N-heterocyclic carbenes were prepared by reaction of (IDipp)PSiMe ₃ (1) (IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) with (IMes)AsCl ₃ (2) (IMes=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) to afford the dichloride [(IMes)As(Cl)P(IDipp)]Cl (3), which upon reduction with KC ₈ furnished heteroleptic [(IMes)AsP(IDipp)] (4). The corresponding mono- and dications [(IMes)AsP(IDipp)][PF ₆ ], [5]PF ₆ , and [(IMes)AsP(IDipp)][GaCl ₄ ] _2, [6][GaCl ₄ ] ₂ , respectively, were prepared by one-electron oxidation of 4 with ferrocenium hexafluorophosphate, [Fc]PF _6, or by chloride abstraction from 3 with two equivalents of GaCl ₃ , respectively. Compounds 4-6 represent rare examples of heterodiatiomic interpnictogen compounds, and X-ray crystal structure determinations together with density functional theory (DFT) calculations reveal a consecutive shortening of the As-P bond lengths and increasing bond order, in agreement with the presence of an arsenic-phosphorus single bond in 4 and a double bond in 6 ²⁺ . The EPR signal of the cationic radical [5] ^+. indicates a symmetric spin distribution on the AsP moiety through strong hyperfine coupling with the ⁷⁵ As and ³¹ P nuclei.
(© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)