Magnesepin, 1,4‐dimagnesocin, 1,4,7‐trimagnesonin, and their C₆H₆Mg_n, n=1‐3, isomers: A density functional computational investigation

Abstract

The seven-, eight-, and nine-membered magnesium-containing heterocycles magnesepin, C 6 H 6 Mg, 1,4-dimagnesocin, C 6 H 6 Mg 2 , and 1,4,7-trimagnesonin, C 6 H 6 Mg 3 , have been examined computationally at the density functional B3LYP/6-311++G** level of theory. The MgH-substituted benzene isomers of these heterocycles [C 6 H 5 MgH; 1,2-; 1,3-; and 1,4-C 6 H 4 (MgH) 2 ; and 1,2,3-; 1,2,4-; and 1,3,5-C 6 H 3 (MgH) 3 ], the mono-and di-MgH-substituted magnesepins [2-; 3-; and 4-C 6 H 5 Mg(MgH) and 2,3-; 2,4-; 2,5-; 2,6-; 2,7-; 3,4-; 3,5-; 3,6-; and 4,5-C 6 H 4 Mg(MgH) 2 ], and the mono-MgHsubstituted 1,4-dimagnesocins [2-; 5-; and 6-C 6 H 5 Mg 2 (MgH)] have also been investigated for comparative purposes. Magnesepin optimizes as a planar heterocyclic triene with no significant aromatic character, while both 1,4-dimagnesocin and 1,4,7-trimagnesonin optimize as nonplanar, twisted molecules. In all cases, the isomeric MgH-substituted benzene systems were found to contain planar rings and were more stable than the isomeric magnesium-containing heterocycles, but the nonplanar mono-MgH-substituted magnesepins were found to be less stable than 1,4-dimagnesocin, and the nonplanar di-MgH-substituted 1,4-dimagnesocins were generally less stable than the mono-MgH-substituted magnesepins and were more stable than 1,4,7-trimagnesonin. Evidence for intramolecular, unsymmetrical μ 2 -bridging hydrogen atoms was observed in those molecules containing adjacent MgH substituents.

Main-Group Metal Complexes of Benzene: Predicted Features of Stabilization and Isomerization

“…Among a huge multitude of such systems, intermolecular complexes of second-group metal atoms (mainly Be and Mg) were previously investigated from the viewpoint of nonlinear optical properties, such as hyperpolarizability [ 1 , 2 ], in relation to astrochemistry and radioastronomy [ 3 , 4 ], metal-containing heterocycles [ 5 ], intra- and intermolecular cooperativity of binding [ 6 ], and as potential units for a charge-governed structure manipulation [ 7 ]. In particular, one such very uncommon compound, diberyllocene (with a Be-Be bond), was produced in experiments very recently [ 8 ].…”