Synthesis and reactivity of N,N-dialkylcarbamato complexes of manganese(II). Crystal and molecular structure of [Mn6(O2CNEt2)12], a hexamer with four five-co-ordinated manganese(II) atoms

Abstract

The compounds [{Mn(O₂CNR₂)₂}_n](R = Me, Et, or Prⁱ) have been prepared by treating [Mn(cp)₂](cp =η⁵-C₅H₅) with CO₂–NHR₂ in organic solvents. These reactions may possibly involve the addition compound [Mn(cp)₂]·NHR₂. In the case of R = Et, the adduct has been isolated and characterized, and the space group, crystal data, and metal connectivity established. The structure of the N,N-diethylcarbamato complex has been solved by X-ray diffraction. Crystal data: monoclinic, space group C2/c, a= 18.546(3), b= 19.287(3), c= 24.877(3)Å, β= 95.38(2)°, R= 0.078. It consists of hexameric units [Mn₆(O₂CNEt₂)₁₂], containing four five-co-ordinated Mn atoms, joined by bridging carbamato ligands. It was found to be unreactive towards nucleophiles, while by reaction with [{Ti(cp)₂Cl}₂] the new complex [Ti(cp)₂(O₂CNEt₂)] has been obtained. Organic electrophiles react regioselectively at the oxygen or at the nitrogen atom of the carbamato ligand of the manganese complexes, and in the former case the CO₂ fragment is retained in the reaction products.