Mono- and bis-ortho-chelated lithium and sodium phenolates. Molecular structures of the first lithium phenolate with a stable, trinuclear structure and of a tetranuclear sodium analog, [MOC6H2(CH2NMe2)2-2,6-Me-4]x (M = Li, x = 3; M = Na, x = 4)

The lithium and sodium phenolates of 2-[ (dimethylamino)methyl]phenol, la and 2a, 2-[(dimethylamino)methyl]-4,6-dimethylphenol, l b and 2b, and 2,6-bis[(dimethylamino)methyl]-4-methylphenol, IC and 2c, respectively, have been synthesized.The structures of these complexes in solution were studied by variable-temperature lH and l3C NMR spectroscopy and cryoscopic molecular weight measurements.The solid-state structures of complexes IC and 2c derived from 2,6-bis[ (dimethylamino)methyl]-4-methylphenol, were determined by X-ray diffraction.The complexes containing only one ortho-chelating (dimethy1amino)methyl group, i.e. la,b and 2a,b, are soluble in weakly polar solvents, like tetrahydrofuran.Complexes la and l b are tetramers in benzene.These tetramers occur in solution in two isomeric forms, Le. as aggregates with 0 2 and S 4 symmetry.The lithium "pincer-phenolate" containing two ortho-chelating (dimethy1amino)methyl groups (IC) is a trimer in apolar solvents as well as in the solid-state.It is the first example of a phenolate complex with a stable, trinuclear structure.In contrast, the sodium analog (2c) is a dimer in solution and crystallizes as a tetramer with a cubic-likeNa404 core.Crystals of Li3C3&N603, lc,aremonoclinic,spacegroupP21/n,withunit celldimensionsa= 42.381(5)A,b=8.8417(11)&~=11.1802(10) A, fi = 90.539(8)", and Z = 4.The structure was refined to R = 0.068 for 4106 reflections and 610 parameters.The trimeric structure contains a Li303-ring which is almost perfectly planar (within 0.05 A), and very short Li-0 and C-0 bond lengths (averages of 1.865(9) and 1.317(6) A, respectively).As a result of intramolecular amine coordination IC is a "propeller-like" molecule with screw-type chirality.Crystals of Na4C52Hg4N8O4.C6H6, 2c, are monoclinic, space group P2/c, with a = 16.021(2)A, b = 10.275(1)A, c = 24.190(2)A, B = 130.35(1)O, 2 = 2, and final R = 0.064 for 3476 reflections and 400 parameters.This tetramer consists of a double dimer in which the NMe2 groups of one dimer do exclusively coordinate to the sodium atoms of the same dimer.