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Remarkable Gallaphosphaketenes as Powerful Phosphorus Transfer Reagents

Phosphaketenes,Phosphorus,Phosphagallenes,Cycloaddition Reactions,Bond Activation Reactions,CO2 Activation,Phosphorus Radicals,Gallium

New Technologies in Phosphorus Chemistry > 4) Inorganic phosphorus chemistry

Phosphaketenes are versatile reagents in organophosphorus chemistry.^[1] We herein describe the synthesis of two novel LGa-substituted phosphaketenes (LGa(Cl)PCO 1, LGa(PCO)₂ 2; L = HC[C(Me)N(2,6-i-Pr₂C6H₃)]₂) and show on their remarkable reactions with Gallanediyl (LGa).^[2,3] Both 1 and 2 react with LGa and yield gallaphosphenes LGa(X)PGaL (X = Cl 3, OCP 4) which selectively activate the polar E−H bonds of ammonia, primary amines, water, phenol, thiophenol, and selenophenol with 1,2 addition at the polar Ga–P double bond.^[3,4] Remarkably, the reactions with ketones proceeded via an unprecedented C(sp³)‒H bond activation.^[2] Even more remarkably, 3 undergoes reversible [2+2] and [2+2+2] cycloaddition reactions with heteroallenes (CO₂, isocyanates, carbodiimides),^[2,5] while chloride abstraction with LiBAr^F₄ yielded a heteronuclear analogue of the allyl cation [LGaPGaL][BAr^F₄] (BAr^F₄ = B(C₆F₅)₄), according to quantum chemical calculations.^[2] Furthermore, the photolysis of 1 yielded a diphosphene [LGa(Cl)P]₂, which reacts with an NHC and undergoes a one-electron oxidation reaction to afford the corresponding diphosphene radical cations.^[6]



References:

1. J. M. Goicoechea, H. Grützmacher, Angew. Chem., Int. Ed. 2018, 57, 16968–16994; Angew. Chem. 2018, 130, 17214–17240.


2. M. K. Sharma, C. Wölper, G. Haberhauer, S. Schulz, Angew. Chem., Int. Ed. 2021, 60, 6784–6790; Angew. Chem. 2021, 133, 6859–6865.


3. M. K. Sharma, C. Wölper, G. Haberhauer, S. Schulz, Angew. Chem. Int. Ed. 2021, 60, 21784‒21788; Angew. Chem. 2021, 40, 21953‒21957.


4. M. K. Sharma, C. Wölper, S. Schulz, Dalton Trans. 2022, 51, 1612-1616.


5. M. K. Sharma, P. Dhawan, C. Helling, C. Wölper, S. Schulz, Chem. Eur. J. 2022, 22, e202200444.


6. M. K. Sharma, S. Chabbra, C. Wölper, H. M. Weinert, A. Schnegg and S. Schulz, Chem. Sci., 2022, 13, 12643-12650.