Terphenyl Substituted Derivatives of Manganese(II): Distorted Geometries and Resistance to Elimination


Reaction of Li(THF)Ar′MnI 2 2 (Ar′ = C 6H 3-2,6-(C 6H 2-2,6- iPr 3) 2) with LiAr′, LiCCR (R = tBu or Ph), or (C 6H 2-2,4,6- iPr 3)MgBr(THF) 2 afforded the diaryl MnAr′ 2 (1), the alkynyl salts Ar′Mn(CC tBu) 4Li(THF) 3 (2) and Ar′Mn(CCPh) 3Li 3(THF)(Et 2O) 2(μ 3-I) (3), and the manganate salt Li(THF)Ar′Mn(μ-I)(C 6H 2-2,4,6- iPr 3) (4), respectively. Complex 4 reacted with one equivalent of (C 6H 2-2,4,6- iPr 3)MgBr(THF) 2 to afford the homoleptic dimer Mn(C 6H 2-2,4,6- iPr 3)(μ-C 6H 2-2,4,6- iPr 3) 2 (5), which resulted from the displacement of the bulkier Ar′ ligand in preference to the halogen. The reaction of the more crowded Li(THF) Ar*MnI 2 2 (Ar* = C 6H 3-2,6-(C 6H 2-2,4,6- iPr 3) 2) with Li tBu gave complex Ar*Mn tBu (6). Complex 1 is a rare monomeric homoleptic two-coordinate diaryl Mn(ii) complex; while 6 displays no tendency to eliminate β-hydrogens from the tBu group because of the stabilization supplied by Ar*. Compounds 2 and 3 have cubane frameworks, which are constructed from a manganese, three carbons from three acetylide ligands, three lithiums, each coordinated by a donor, plus either a carbon from a further acetylide ligand (2) or an iodide (3). The Mn(ii) atom in 4 has an unusual distorted T-shaped geometry while the dimeric 5 features trigonal planar manganese coordination. The chloride substituted complex Li 2(THF) 3Ar′MnCl 2 2 (7), which has a structure very similar to that of Li(THF)Ar′MnI 2 2, was also prepared for use as a possible starting material. However, its generally lower solubility rendered it less useful than the iodo salt. Complexes 1-7 were characterized by X-ray crystallography and UV-vis spectroscopy. Magnetic studies of 2-4 and 6 showed that they have 3d 5 high-spin configurations. © The Royal Society of Chemistry 2010.



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