A Mixed-Valence Tri-Zinc Complex, [LZnZnZnL] (L = Bulky Amide), Bearing a Linear Chain of Two-Coordinate Zinc Atoms

Reduction of a variety of extremely bulky amido Group 12 metal halide complexes, [LMX(THF)(0,1)] (L = amide; M = Zn, Cd, or Hg; X= halide) with a magnesium(I) dimer gave a homologous series of two-coordinate metal(I) dimers, [L'MML'] (L'=N(Ar dagger)(SiMe3), Ar dagger= C6H2{C(H)Ph-2}(2)Pr-i-2,6,4); and the formally zinc(0) complex, [L*ZnMg((Mes)Nacnac)] (L*= N(Ar*)(SiPr3i); Ar*= C6H2{C(H)Ph-2}(2)Me-2,6,4; (Mes)Nacnac=[(MesNCMe)(2)CH](-), Mes= mesityl), which contains the first unsupported Zn-Mg bond. Two equivalents of [L*ZnMg((Mes)Nacnac)] react with ZnBr2 or ZnBr2(tmeda) to give the mixed valence, two-coordinate, linear tri-zinc complex, [L*(ZnZnZnL)-Zn-I-Zn-0-L-I*], and the first zinc(I) halide complex, [L*ZnZnBr(tmeda)], respectively. The analogues [L*ZnMZnL*] (M= Cd or Hg), were also prepared, the Cd species contains the first Zn-Cd bond in a molecular compound. Metal-metal bonding was studied by DFT calculations.