Reactivity of bulky Ln(ii) amidinates towards P4, As4, and As4S4.

The reduction of P4, As4 and As4S4 (realgar) with the sterically encumbered reductants [(DippForm)2Ln(thf)2] (Ln = Sm, Yb; DippForm = {(2,6-iPr2C6H3)NC(H) = N(2,6-iPr2C6H3)}-) is reported. For the first time, purely f-element containing inverse inorganic sandwich complexes [{(DippForm)2Sm}2(μ2-η4:η4-E4)] (E = P, As), featuring a π-aromatic cyclo [E4]2- middle deck, were obtained upon reaction with P4 and As4. The reaction with realgar leads to a cage disruption and the formation of the unusual species [{(DippForm)(DippForm-AsS2)}Ln(thf)]. The reactivity of divalent Ln amidinates towards main group molecules is in comparison to metallocenes faster, more efficient and thus significantly influenced by the ligand environment. Experimental results are supported by DFT calculations.