Diverse Reactions of α‐Diimine‐Ligated MgI−MgI‐Bonded Compound with Carbodiimides

The α‐diimine‐ligated dimagnesium(I) compound [K(thf)3]2[LMg−MgL] (1, L=[(2,6‐iPr2C6H3)NC(Me)]22−) displays diverse reactivities toward carbodiimides (RN=C=NR) with different R substituents. In the reaction of 1 with Me3SiNCNSiMe3, one of the easily leaving trimethylsilyl groups is lost to yield the Me3SiNCN− moiety that either bridges two MgII 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 [C2(NR)4]2− diamido moiety, which bridges two Mg centers, giving complexes [{K(dme)2}2LMg(μ‐{C2(NR)4})MgL] (6, R=Cy; 7, R=iPr) and [L⋅−Mg(μ‐{C2(NR)4})MgL⋅−] (8). Most interestingly, upon treating 1 with Me3SiC≡CSiMe3, the acetylide complex [K(dme)][LMg(C≡CSiMe3)(dme)] (9) was prepared, which undergoes a rare “double insertion” with CyNCNCy to afford [K(solv)][K(dme)2LMg(NCy)2C−C≡C−C(NCy)2MgL] (10) containing an acetylenediide‐coupled bis(amidinate) ligand that bridges two Mg atoms. Diverse reaction types: Reactions of dimagnesium(I) [LMg−MgL] (L=α‐diimine) with carbodiimides proceed via four pathways: 1) Release of one Me3Si of Me3SiNCNSiMe3 to yield either bridging or mononuclear complexes; 2) N=C=N insertion into the Mg−Mg bond; 3) coupling of two carbodiimides; and 4) double insertion of carbodiimides into a Mg−C bond to form an alkyne‐bridged bis(amidinate) [(NCy)2C−C≡C−C(NCy)2]2−.