Activation of N2O and SO2 by the P-B Bond System. Reversible Binding of SO2 by the P-O-B Geminal Frustrated Lewis Pair.

Natalia Szynkiewicz,Rafał Grubba,Jarosław Chojnacki

doi:10.1021/acs.inorgchem.0c00435

Natalia Szynkiewicz, Rafał Grubba + Show 1 more

Open Access

https://doi.org/10.1021/acs.inorgchem.0c00435

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Journal: Inorganic chemistry	Publication Date: Apr 14, 2020
Citations: 24	License type: cc-by

Affiliation: Gdańsk University of Technology

Abstract

Herein, we present the first transformation of borylphosphine into borylphosphinite using nitrous oxide. Borylphosphine reacts with N2O via insertion of a single oxygen atom into the P–B bond and formation of a P–O–B bond system. Borylphosphine and borylphosphinite capture SO2 and activate it in an irreversible and reversible manner, respectively.

Highlights

Metal-free catalysis based on systems that mimic the reactivity of transition metal compounds toward hydrogen and greenhouse gases is currently one of the most widely studied fields of main-group element chemistry.[1,2] We are searching for compounds that capture small molecules and enable their clean and efficient conversion into complex organic derivatives or their decomposition into more environmentally friendly species
N2O may be achieved by N-heterocyclic carbenes (NHCs),[7,8] leading to the formation of stable adducts involving an intact N2O moiety: R3PNNOBR3 or NHCNNO, respectively
X-ray structure determination unambiguously confirmed the identity of 2 and showed that a single oxygen atom was inserted into the P−B bond (Figure 1)

Summary

INTRODUCTION

Metal-free catalysis based on systems that mimic the reactivity of transition metal compounds toward hydrogen and greenhouse gases is currently one of the most widely studied fields of main-group element chemistry.[1,2] We are searching for compounds that capture small molecules and enable their clean and efficient conversion into complex organic derivatives or their decomposition into more environmentally friendly species. SO2 reacts with a wide range of organic species, typically as an oxidizing agent, and forms stable adducts with amines, of which solid adducts are utilized as handled sulfur dioxide surrogates in organic syntheses.[10] While nitrogen base−SO2 adducts are well characterized, reaction with phosphines results in the formation of phosphine oxides and phosphine sulfides in a 2:1 ratio.[11] Very recently, Dielmann et al isolated the first phosphine−SO2 adducts.[12] The slow decomposition of these compounds helped to elucidate the mechanism of their oxidation: nucleophilic attack by the phosphine at the sulfur atom of SO2 followed by the formation of a P−O bond with elimination of SO.[12] Phosphine−SO2 adducts may be stabilized in the presence of Lewis acids, for instance, by using FLPs. Inter- and intramolecular FLPs bind SO2, yielding the corresponding R3P/N−S(O)−O−B/SiR3 as a linear or cyclic zwitterions upon formation of P−S (or N−S) and B−O (or Si−O and Al−O) bonds, respectively.[13−15] Unlike FLPs, stable boryl(phosphino)carbene was found to capture and to activate the SO2 molecule in an unprecedented manner, giving sulfine derivatives R2P(O)− C(SO)−BR2.16. From a series of monomeric diaminophosphinoboranes recently synthesized by us, we tested the reactivity of tBu2P−B(NiPr2)[2] (1)[19] due to its high nucleophilicity and the presence of tBu and NiPr2 substituents, which should promote the crystallization of activation products

RESULTS AND DISCUSSION

CONCLUSIONS

EXPERIMENTAL SECTION

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