A bis(silylene)pyridine pincer ligand can stabilize mononuclear manganese(0) complexes: facile access to isolable analogues of the elusive d(7)-Mn(CO)(5) radical

Using the potentially tridentate N,N'-bis(N-heterocyclic silylene)pyridine [SiNSi] pincer-type ligand, 2,6-N,N'-diethyl-bis[N,N'-di-tert-butyl(phenylamidinato)silylene] diaminopyridine, led to the first isolable bis(silylene)pyridine-stabilized manganese(0) complex, {kappa(3)-[SiNSi]Mn(dmpe)} 4 (dmpe = (Me2P)(2)C2H4), which represents an isolobal 17 VE analogue of the elusive Mn(CO)(5) radical. The compound is accessible through the reductive dehalogenation of the corresponding dihalido (SiNSi)Mn(II) complexes 1 (Cl) and 2 (Br) with potassium graphite. Exposing 4 towards the stronger pi-acceptor ligands CO and 2,6-dimethylphenyl isocyanide afforded the related Mn(0) complexes kappa(2)-[SiNSi]Mn(CO)(3) (5) and kappa(3)-[SiNSi] Mn(CNXylyl)(2)(kappa(1)-dmpe) (6), respectively. Remarkably, the stabilization of Mn(0) in the coordination sphere of the [SiNSi] ligand favors the d(7) low-spin electronic configuration, as suggested by EPR spectroscopy, SQUID measurements and DFT calculations. The suitability of 4 acting as a superior pre-catalyst in regioselective hydroboration of quinolines has also been demonstrated.