An Alkali-Metal Halide-Bridged Actinide Phosphinidiide Complex

The salt metathesis reaction of the thorium methyl chloride complex [η⁵-1,3-(Me₃C)₂C₅H₃]₂Th(Cl)Me (3) with 2,4,6-(Me₃C)₃C₆H₂PHK in benzene furnishes an alkali-metal halide-bridged phosphinidiide actinide metallocene, {[η⁵-1,3-(Me₃C)₂C₅H₃]₂Th(═P-2,4,6- ^tBu₃C₆H₂)(ClK)}₂ (4), whose structure and reactivity was investigated in detail. On the basis of density functional theory (DFT) studies, the 5f orbitals in the model complex [η⁵-1,3-(Me₃C)₂C₅H₃]₂Th(═P-2,4,6- ^tBu₃C₆H₂) (4') contribute significantly to the bonding of the phosphinidene Th═P(2,4,6- ^tBu₃C₆H₂) moiety. Furthermore, compared to the related thorium imido complex, the bonds between the [η⁵-1,3-(Me₃C)₃C₅H₂]₂Th²⁺ and [P-2,4,6- ^tBu₃C₆H₂]^2- fragments are more covalent. The reactivity of compound 4 toward alkynes and a variety of heterounsaturated molecules such as nitriles, isonitriles, carbodiimides, imines, isothiocyanates, aldehydes, ketones, thiazoles, quinolines, organic azides, pyridines, and imidazoles, forming metallacycles, phospholes, imidos, metallaheterocycles, sulfidos, oxidos, pinacolates, pseudophosphinimidos, and phosphidos, was comprehensively studied. Moreover, complex 4 reacts with elemental selenium and PhSSPh, yielding selenido and sulfido compounds, respectively. DFT computations were performed to complement these experimental investigations and to provide further insights.