Synthesis and reactivity of a six-membered heterocyclic 1,3-diphosphaallene

Mahendra K Sharma; Christoph Wölper; Hannah Siera; Gebhard Haberhauer; Stephan Schulz

doi:10.1039/d4sc06371f

Synthesis and reactivity of a six-membered heterocyclic 1,3-diphosphaallene

Chem Sci. 2024 Nov 29. doi: 10.1039/d4sc06371f. Online ahead of print.

Authors

Mahendra K Sharma¹, Christoph Wölper¹, Hannah Siera², Gebhard Haberhauer², Stephan Schulz^{1

3}

Affiliations

¹ Institute of Inorganic Chemistry, University of Duisburg-Essen Universitätsstraße 5-7 D-45141 Essen Germany [email protected] https://www.uni-due.de/ak_schulz/index_en.php.
² Institute of Organic Chemistry, University of Duisburg-Essen Universitätsstraße 5-7 D-45141 Essen Germany.
³ Center for Nanointegration Duisburg-Essen (CENIDE), University of Duisburg-Essen Carl-Benz-Straße 199 47057 Duisburg Germany.

Abstract

1,3-Diphosphaallenes are a new class of heavier heteroallenes and show a fascinating chemical behavior and reactivity. Herein we report on the room temperature transformation of gallaphosphene LGa(OCP)PGaL 1 (L = HC[C(Me)N(Ar)]₂, Ar = 2,6-i-Pr₂C₆H₃) to the six-membered metallaheterocycle LGa(PCP)OGaL 2 featuring a LGa-substituted 1,3-diphosphaallene unit. The possible mechanism of formation of 2 is supported by quantum chemical calculations, which revealed that the formation of 2 is energetically more favorable (ca. 2 kcal mol^-1) than the formation of 1 at ambient temperature. Remarkably, 2 reacts with singlet carbenes selectively to new five-membered metallaheterocycles LGa(PC)OGaL(P)NHC (NHC = [CMeN(R)]₂C; R = Me 3, ⁱPr 4; C{(NAr)CMe₂CH₂CMe₂ = cAAC (5) featuring a 1,3-diphospha-1,3-butadiene unit. In stark contrast, its reaction with trimethylsilyldiazomethane yields (LGa)₂O(P₂C₂H)SiMe₃6 featuring a 1,3-diphosphacyclobutene unit. Compounds 2-6 were characterized by heteronuclear NMR (¹H, ¹³C, ³¹P), UV-vis, and IR spectroscopy. Compounds 2-4 and 6 were also characterized by single crystal X-ray diffraction (sc-XRD) and their bonding nature was investigated by quantum chemical calculations.