Diverse Reactions of α-Diimine-Ligated Mg -Mg -Bonded Compound with Carbodiimides.

The α-diimine-ligated dimagnesium(I) compound [K(thf) ] [LMg-MgL] (1, L=[(2,6-iPr C H )NC(Me)] ) displays diverse reactivities toward carbodiimides (RN=C=NR) with different R substituents. In the reaction of 1 with Me SiNCNSiMe , one of the easily leaving trimethylsilyl groups is lost to yield the Me SiNCN moiety that either bridges two Mg centers (2) or terminally coordinated (3). In contrast, with the similarly bulky tBuNCNtBu, the carbodiimide inserts into Mg-Mg bond with accompanying C-H activation of a ligand or solvent (products 4 and 5). In the case of dicyclohexyl or diisopropyl carbodiimide, reductive C-C coupling of two RNCNR molecules occurs to form the [C (NR) ] diamido moiety, which bridges two Mg centers, giving complexes [{K(dme) } LMg(μ-{C (NR) })MgL] (6, R=Cy; 7, R=iPr) and [L⋅ Mg(μ-{C (NR) })MgL⋅ ] (8). Most interestingly, upon treating 1 with Me SiC≡CSiMe , the acetylide complex [K(dme)][LMg(C≡CSiMe )(dme)] (9) was prepared, which undergoes a rare "double insertion" with CyNCNCy to afford [K(solv)][K(dme) LMg(NCy) C-C≡C-C(NCy) MgL] (10) containing an acetylenediide-coupled bis(amidinate) ligand that bridges two Mg atoms.