Preparation, Characterization, and Theoretical Analysis of Group 14 Element(I) Dimers: A Case Study of Magnesium(I) Compounds as Reducing Agents in Inorganic Synthesis

A synthetic route to the new amidine (DipNH)(DipN)C(C6H4But-4) (ButisoH; Dip = C6H3Pri2-2,6) has been developed. Its deprotonation with either LiBun or KN(SiMe3)2 yields the amidinate complexes [M(Butiso)] (M = Li or K). Their reactions with group 14 element halides/pseudohalides afford the heteroleptic group 14 complexes [(Butiso)SiCl3], [(Butiso)ECl] (E = Ge or Sn), and [{(Butiso)Pb(μ-O3SCF3)(THF)}∞], all of which have been crystallographically characterized. In addition, the synthesis and spectroscopic characterization of the homoleptic complex [Pb(Butiso)2] is reported. Reductions of the heteroleptic complexes with a soluble magnesium(I) dimer, [{(MesNacnac)Mg}2] (MesNacnac = [(MesNCMe)2CH]−; Mes = mesityl), have given moderate-to-high yields of the group 14 element(I) dimers [{(Butiso)E}2] (E = Si, Ge, or Sn), the X-ray crystallographic studies of which reveal trans-bent structures. The corresponding lead(I) complex could not be prepared. Comprehensive spectroscopic and theoretical analyses of [{(Butiso)E}2] have allowed their properties to be compared. All complexes possess E–E single bonds and can be considered as intramolecularly base-stabilized examples of ditetrelynes, REER. Taken as a whole, this study highlights the synthetic utility of soluble and easy to prepare magnesium(I) dimers as valuable alternatives to the harsh, and often insoluble, alkali-metal reducing agents that are currently widely employed in the synthesis of low-oxidation-state organometallic/inorganic complexes.