Developments in Heterobimetallic s-Block Systems: Synthesis and Structural Survey of Molecular M/Ae (M = Li, Na, K, Cs; Ae = Ca, Sr) Aryloxo Complexes

Abstract

A series of novel heterobimetallic group 1/strontium and group 1/calcium aryloxo complexes having the composition [MAe(Odpp)3] [Ae=Sr and M=Na (1), K (2, 3), Cs (4); Ae=Ca and M=Na (5), K (6), Cs (7)] or [M2Ae(Odpp)4] [M=Li and Ae=Sr (9), Ca (10)] have been prepared using 2,6-diphenylphenol (HOdpp) as the ligand. Through the use of solid-state direct metalation, these compounds were obtained either directly from the reaction vessel or after workup in toluene. The Lewis base adduct [KCa(Odpp)3(thf)] (8) was obtained by treatment of [KCa(Odpp)3] (6) with tetrahydrofuran (thf). All of the compounds displayed extensive metal-pi-arene interactions, which provide significant stabilization in these reactive species. The thermal stabilities and volatilities of representative heterobimetallic strontium and calcium complexes were investigated using thermogravimetric analysis.

Lithium Aryloxo Magnesiates: an Examination of Ligand Size and Donor Effects

“…Compounds 4 and 5 share the sameLi 2 MgR 4 coreasthearyloxomagnesiate[Li(TMEDA) 2 Mg-(2-MeOC 6 H 4 ) 4 ], 14 which may be rationalized by the comparable ligand sizes. This structural motif is also known for several previously reported magnesiates using amide, alkyl, and enolate ligands, 21,35 as well as in the mixed Li/Ba, 16 Li/ Sr, 36 Attempts to prepare a THF solvate using m-HOdtp, which afforded the TMEDA solvate 5, yielded 6 as depicted in Figure 6. Instead of the 2:1 Li/Mg ratio as seen in 5, compound 6 displays an unprecedented 2:3 Li/Mg stoichiometry.…”

“…21 The common structural motif in compounds 2-6 is the doubly bridging aryloxide moiety pattern also seen in heterobimetallic compounds involving combinations of lithium with heavier alkaline earth metals calcium, strontium, and barium bearing the HOdpp ligand. 16,36 Interestingly, the triply bridging moiety, as observed for the heavier alkali metals, is absent for lithium, likely a consequence of the small size of the metals. As such, lithium is unable to support a facesharing motif.…”

Advances in alkaline earth-nitrogen chemistry

“…Metal· · ·C() interactions are a prevalent stabilizing force in alkaline earth metal chemistry [13][14][15][16], as summarized in Table 1. However, less is known about the role that agostic interactions of the type M· · ·H-C play in stabilizing these metal centers.…”

π-Coordination as a structure determining principle: structural characterization of [K(Odpp)]∞, and {[K2(Odpp)2H2O]2}∞

“…The capacity of steric saturation of metal centers through secondary interactions, such as MÀ ÀCp interactions, has been recently demonstrated by a series of monoand heterobimetallic compounds based on the 2,6-diphenylphenol (HOdpp) ligand [1][2][3][4][5][6]. In these complexes, extensive metal-Cp interactions support the low metal coordination numbers.…”

“…Anhydrous tetrahydrofuran (THF) and toluene were obtained utilizing the VAC atmospheres DRI-SOLV solvent system and degassed using three freeze/thaw cycles. Compounds 1 and 2 were isolated from reaction mixtures containing either Na and K aryloxides (1), or Li and K aryloxides (2), as described in detail below. Lithium aryloxide was obtained as described, but the sodium and potassium metal aryloxides (MOdpp, M ¼ Li, Na, K) were prepared using modified literature procedures [6], by refluxing the metals in toluene in the presence of 2,6-diphenylphenol.…”