Metallaphosphaketenes with the general formula M‒P=C=O (M = p- and d-block metal) contain weak P‒C bonds. These compounds can serve as versatile reagents in organophosphorus chemistry. While several mono-phosphaketenes have been prepared, bis-phosphaketenes had remained unknown so far.
Stephan Schulz, University of Duisburg-Essen, Germany, and colleagues have prepared the first metal bis-phosphaketenes LM(PCO)2 (pictured above; M = Ga, In; L = HC[C(Me)N(Ar)]2; Ar = 2,6-i-Pr2C6H3). The compounds were prepared via salt elimination reactions of β-diketiminate-stabilized group-13 dihalides of the type LMCl2 with two equivalents of Na(OCP)(dioxane)2.5.
The products were fully characterized using NMR and infrared (IR) spectroscopy and single-crystal X-ray diffraction analysis. Reactivity studies showed that the metal bis-phosphaketenes undergo CO elimination reactions upon treatment with the gallanediyl LGa to give unprecedented group-13 metallaphosphenes of the type LGa(OCP)PML (pictured below; M = Ga, In). Both of these metallaphosphenes were found to readily activate polar X‒H bonds (X = N, O) in small molecules such as aniline and phenol. This work demonstrates the synthetic potential of LM(PCO)2 as a possible new class of reagents for organophosphorus chemistry.
- Bis‐phosphaketenes LM(PCO)2 (M = Ga, In): A new class of reactive group 13 metal–phosphorous compounds,
Mahendra K. Sharma, Pratima Dhawan, Christoph Helling, Christoph Wölper, Stephan Schulz,
Chem. Eur. J. 2022.