The Recently Synthesized Dimagnesiabutadiene and the Analogous Dimetalla‐Beryllium, ‐Calcium, ‐Strontium, and ‐Barium Compounds

Abstract

The 2014 synthesis of the remarkable dimagnesium compound Mg [C (CH ) (Si(CH ) ) ](C H ) (C H O) may point the way to a new chapter in alkaline earth organometallic chemistry. Accordingly, we have studied the known Mg compound and the analogous Be, Ca, Sr, and Ba structures. Although most of our theoretical predictions come from density functional methods, the latter have been benchmarked using coupled cluster theory including single, double, and perturbative triplet excitations, CCSD(T) using cc-pVTZ basis sets. Among our most important predictions are the energies for dissociation to the butadiene plus the RM-MR [R=(C H ) (C H O) ; M=Be, Mg, Ca, Si, and Ba] entities. The most reliable predictions for the dissociation energies are 99-104 (Be), 85-93 (Mg), 90-99 (Ca), 83-92 (Sr), and 83-94 (Ba) kcal mol . Thus, there is reason to anticipate that the four unknown compounds should be achievable synthetically. The predicted metal-metal distances (not single bonds) are 2.89 Å (Mg⋅⋅⋅Mg), 3.46 Å (Ca⋅⋅⋅Ca), 3.75 Å (Sr⋅⋅⋅Sr), and 4.04 Å (Ba⋅⋅⋅Ba). The separated RM-MR compounds have longer M-M distances but genuine metal-metal single bonds. This perhaps counter intuitive result is due to the presence of the bridging carbons in the alkaline earth butadiene compounds. All five compounds incorporate metal-carbon ionic interactions.

Synthesis and Structural Characterization of Butadienylcalcium‐based Heavy Grignard Reagents and a Ca4[O] Inverse Crown Ether Complex

“…Thel engths of (sp 2 )CÀCa bonds are in the range from 2.545(6) (C4ÀCa2) to 2.584(6) (C1ÀCa2), which are close to those of 2.The short distance between Ca1 and Ca2 (3.3632 (18) )i ndicates aw eak Ca À Ca interaction. [14] Theb ite angles 70.6(2)8 8 (C1-Ca1-C4) and 70.2(2)8 8 (C1-Ca2-C4) are also relatively small but close to that of 2. Thes tructure of 4 shown in Figure 3, the structural parameters of which are close to those of 3,c an be interpreted as ad imer of 3 with the ligation of 2.0 equiv of LiI.…”

Comparative Study of the Thermal Stabilities of the Experimentally Known High-Valent Fe(IV) Compounds Fe(1-norbornyl)4 and Fe(cyclohexyl)4

“…London dispersion forces, which are always present, become significant enough to influence the stability, structure, and reactivity of inorganic and organometallic derivatives bearing sterically large groups. The London dispersion forces in such molecules with bulky organic groups are sufficient to hold the molecule together. − In addition, for compounds containing high-valent metal centers, the strong Coulombic interactions, resulting from the high charge density on the metal atoms can also significantly affect their stabilities. The competition between dispersion and electrostatic interactions may simultaneously determine the chemical and physical properties of the inorganic and organometallic derivatives.…”

Synthesis and Structural Characterization of Butadienylcalcium‐based Heavy Grignard Reagents and a Ca4[O] Inverse Crown Ether Complex

“…ORTEP drawing of the central anionic framework of 7 with ellipsoids set at 30 %p robability. [18] Hydrogen atoms, carbon atoms in coordinated THF molecules and peripheralc ounterions are omitted for clarity.S elected bond lengths []and angles [8 8]: C1-C2 1.329 (14), C2-C3 1.542 (15), C3-C4 1.304 (13), C1-Ca1 2.644(10), C4-Ca1 2.909(10), C1-Ca2 2.671(10), C4-Ca2 2.723(10), Ca1-I1 3.230(3), Ca1-I2' 3.237-(2), Ca2-I2 3.172(3), Ca2-I1' 3.247(2), Ca1-Ca2 3.093(3), Ca1-Ca2' 3.515(3), Ca1-O1 2.332(2), Ca2-O1 2.349(2), Ca1-O2 2.366(8), Ca2-O3 2.361(8);C1-Ca1-C4 67.5(3), C1-Ca2-C4 70.0(3), Ca2-Ca1-Ca2' 90.38 (7), Ca1-Ca2-Ca1' 89.62 (7), Ca1-O1-Ca2 82.70(8), Ca1-O1-Ca2' 97.30(8).…”