Alkali-metal-mediated manganation(II) of naphthalenes: constructing metal la-anthracene and metalla-phenanthrene structures

Alkali-metal-mediated manganation (AMMMn) reactions of the synergic base sodium monoalkyl-bisamidomanganate [(tmeda)Na(tmp)(CH2SiMe3)Mn(tmp)] (1) with naphthalene, 1-methoxynaphthalene, or 2-methoxynaphthalene are reported. These novel direct manganation [Mn(II)] reactions produced the crystalline ortho-manganated naphthyl products [(tmeda)Na(tmp)(2-C10H7)Mn(tmp)] (3), [(tmeda)Na(tmp){2-(1-MeOC10H6)}Mn(CH2SiMe3)] (4), and [(tmeda)Na(tmp){3-(2-MeOC10H6)}Mn(tmp)] (5) in reasonable to good isolated yields of 88, 65, and 85%, respectively. All three new complexes have been crystallographically characterized, showing discrete molecular structures with trigonal planar Mn centers forming σ bonds to the deprotonated C atoms of the naphthyl ligands, whereas Na interacts with the aromatic π system in 3 or with the MeO substituent in 4 and 5. These latter interactions lead to interesting 5,6,7,8-tetrahydrophenanthrene-like and 1,2,3,4-tetrahydroanthracene-like metallacyclic motifs in 4 and 5, respectively. The sensitivity of these AMMMn reactions to impurities has been illustrated in the serendipitous preparation of the benzenediide complex [(tmeda)2Na2(tmp)2(1,4-C6H4)Mn2(tmp)2] (6) from one attempted repeat synthesis of 5. An 'open inverse crown' arrangement with a 1,4-dimanganated benzene molecule is revealed in the crystal structure of 6.