Syntheses, Structures, and Bonding Analyses of Carbenestabilized Stibinidenes

Reactions of two equivalents of LGa {L = HC[C(Me)NAr]2; Ar = 2,6‐iPr2‐C6H3} with SbX3 (X = Cl, Br) yield double‐inserted products (LGaX)2SbX (X = Cl 1, Br 2), which were isolated at –40 °C. Warming solutions of 1 and 2 to ambient temperature results in intramolecular elimination of LGaX2 and formation of Ga‐substituted stibinidenes L(X)GaSb as reaction intermediates, which were stabilized by coordination of strong σ‐donating carbenes. Four carbene‐stabilized stibinidenes MeCAAC‐SbGa(X)L {MeCAAC = [H2C(CMe2)2NAr]C, Ar = 2,6‐iPr2‐C6H3, X = Cl 3, Br 4} and IDipp‐SbGa(X)L {IDipp = 1,3‐bis(2,6‐diisopropylphenyl)‐imidazol‐2‐ylidene, X = Cl 5, Br 6} were characterized by single‐crystal X‐ray diffraction and the nature of the bonding in 36 was further investigated by quantum chemical methods. The studies reveal substantial Sb–Ccarbene π‐backbonding contributions in 3 and 4, whereas the IDipp‐stabilized derivatives 5 and 6 exhibit Sb–Ccarbene single bonds. DFT computations with and without dispersion corrections reveal that dispersion interactions mainly from the bulky aryl groups decisively contribute to the stability of 36.

Dedicated to Prof. E. Niecke on the occasion of his 80th birthday.


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