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

Abstract

Arsenic monophosphide (AsP) species supported by two different N‐heterocyclic carbenes were prepared by reaction of (IDipp)PSiMe3 (1) (IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene) with (IMes)AsCl3 (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 KC8 furnished heteroleptic [(IMes)AsP(IDipp)] (4). The corresponding mono‐ and dications [(IMes)AsP(IDipp)][PF6], [5]PF6, and [(IMes)AsP(IDipp)][GaCl4]2, [6][GaCl4]2, respectively, were prepared by one‐electron oxidation of 4 with ferrocenium hexafluorophosphate, [Fc]PF6, or by chloride abstraction from 3 with two equivalents of GaCl3, 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 75As and 31P nuclei.