Signet-Ring-Shaped Octaphosphorus-Cobalt Complexes: Synthesis, Structure, and Functionalization Reactions with Carbene Analogs

Chengbo Yang; Xuebin Jiang; Qi Chen; Xuebing Leng; Jie Xiao; Shengfa Ye; Liang Deng

doi:10.1021/jacs.2c08647

Signet-Ring-Shaped Octaphosphorus-Cobalt Complexes: Synthesis, Structure, and Functionalization Reactions with Carbene Analogs

J Am Chem Soc. 2022 Nov 16;144(45):20785-20796. doi: 10.1021/jacs.2c08647. Epub 2022 Nov 2.

Authors

Chengbo Yang¹, Xuebin Jiang², Qi Chen¹, Xuebing Leng¹, Jie Xiao¹, Shengfa Ye², Liang Deng^{1

3}

Affiliations

¹ State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai, 200032, China.
² State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Dalian 116023, China.
³ School of Chemistry and Materials Science, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, 1 Sub-lane Xiangshan, Hangzhou 310024, China.

PMID: 36322575
DOI: 10.1021/jacs.2c08647

Abstract

White phosphorus activation with low-valent metal species has proved to be very effective in converting P₄ into small P_n-containing molecules with n ≤ 4. Much less developed are metal-mediated P₄-coupling reactions that can yield selectively large polyphosphorus clusters. Herein, we report P₄-activation reactions with three-coordinate N-heterocyclic carbene(NHC)-cobalt(0)-alkene complexes, which produce the P₈ complexes of cobalt [(NHC)₂Co₂(μ-η⁶:η⁶-P₈)] (NHC = 1,3-dimesitylimidazol-2-ylidene (IMes), 1; 1,3-bis(2,6-diethylphenyl)imidazol-2-ylidene (IDep), 2) in high yields. The P₈ ligand in 1 and 2 exhibits a signet-ring type structure that was predicted by theoretical study but has never been obtained in synthetic molecules. Theoretical studies suggest that [(NHC)₂Co₂(μ-η⁶:η⁶-P₈)] is best described as a Co⁰-[P₈]⁰-Co⁰ complex featuring a Co-Co σ-bond and discernible Co-to-P₈ back-donation. By treating with N-heterocyclic silylene, phosphinidene precursor, organic azides, and NHCs, complex 1 was transformed into [(IMes)₂Co₂(μ-η⁶:η⁶-P₈X)] (X = 1,3-bis(tert-butyl)-1,3-diaza-2-silacyclopent-4-en-2-ylidene, 3; PNMe₂, 4), [(IMes)₂Co₂(σ:(μ-η⁴:η⁶)-RNPPP₆)] (R = SO₂-C₆H₄-p-Me, 5; C(CF₃)₂Ph, 6), and [(IMes)₂Co₂(μ-η²:η²-cyclo-P₄P(IPrⁱ₂))(μ-η³:η³-P₃)] (7), respectively. Complexes 3-7 can be viewed as the adducts of 1 with the corresponding carbene analogous SiR₂, PR, NR, and CR₂, but their core structures are distinct. Under similar conditions, white phosphorus is inert toward these reagents. These cage functionalization reactions showcase the enhanced reactivity of the P₈ ligand in [(NHC)₂Co₂(μ-η⁶:η⁶-P₈)] over that of P₄, and indicate the amphiphilicity of the P₈ ligand toward electrophiles and nucleophiles.