Crystalline Half-Parent Vinyl-tetrylenes: Synthesis and Coordination Chemistry

A family of stable, crystalline half-parent vinyl-tetrylenes ^RL(C₂H₃)E: (4-6; ^RL = {[R₂PCH₂Si(ⁱPr)₂](Dipp)N}^-; Dipp = 2,6-ⁱPr₂C₆H₃; R = Ph, Cy) is reported, accessed via a straightforward salt-metathesis pathway, and their electronic properties and initial reactivity explored. All compounds display downfield-shifted signals in both the ¹H and ¹³C NMR spectra for their [C₂H₃] ligand, being most extreme for Pb due to relativistic effects. UV-vis spectra of compounds 4-6 reveal bathochromic shifts relative to the halo-tetrylene derivatives (i.e., ^RLEX; X = Cl, Br), due to stabilization of the LUMO through overlap of the E-centered p-orbital and the π*-orbital of the [C₂H₃] unit. Vinyl group elimination is demonstrated in the plumbylene system, whereby reaction with the strong electrophile [Ph₃C][BAr^F₄] (Ar^F = 3,5-(CF₃)₂C₆H₃) afforded low-coordinate Pb^II cation 7, stabilized by the chelating ligand and secondary interactions with the weakly coordinating BAr^F₄ anion. Finally, addition of vinyl-germylenes (4) to Ni⁰ synthons enabled the synthesis of mono- and bis(vinylgermylene)-nickel(0) complexes 8 and 9, whereby binding occurs through the tetryl centers and not the vinyl fragment, representing the first examples of vinyl-tetrylene coordination complexes reported to date.