Bimetallic Complexes with Unusual Main Group Bridging Ligands

We report the synthesis and characterization of several mono- and bimetallic complexes with uncommon phosphorus and germanium bonding motifs. These complexes were accessed from two different rhenium compounds: the metalate Na[(BDI)ReCp] and the terminal nitride (BDI)Re(≡N)(η³-Cp) (BDI = N,N'-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate). The reaction of three equivalents of Na[(BDI)ReCp] with one equivalent of PCl₃ generates a neutral, open shell bridging phosphido complex [{(BDI)ReCp}₂(μ-P)]^•, for which the cationic closed shell analogue is readily accessible. The reaction of this same metalate with an equimolar amount of the dioxane adduct of GeCl₂ was found to yield a stable, unsupported chlorometallogermylene complex. Investigations of this complex revealed unintuitive synthetic routes to a trichlorogermyl complex and a germanium-substituted triketimine complex. Using the same chlorometallogermylene complex as a starting material, rational syntheses of an aminometallogermylene complex and a heterobimetallic μ-germanido complex were achieved. The reactions of two equivalents of (BDI)Re(≡N)(η³-Cp) with phosphorus and germanium main group electrophiles gave cationic dirhenium complexes bridged by a {NEN} fragment (E = P, GeCl). We have undertaken these investigations with a focus on how π-bonding with the main group element stabilizes the complexes and facilitates electronic delocalization.