New Structural Features in Heavy Alkaline Earth‐Metal Chemistry — Molecular Heterobimetallic Group 1, Ba Complexes

Abstract

The preparation of heterobimetallic complexes consisting of alkali and heavy alkaline earth metals remains a challenge due to limited available synthetic strategies. Here we present a new class of group 1, Ba compounds of the type [M(n){Ba(Odpp)(2+n)}] (M=Na(n=1) (1), K(n=1) (2), Cs(n=1) (3), Li(n=2) (4); HOdpp=2,6-diphenylphenol) and the Lewis base adducts [Li(2)(thf)(2){Ba(Odpp)(4)}]PhMe (5) and [K{Ba(Odpp)(3)(diglyme)}] (6) (diglyme=[bis(2-methoxy)ethyl ether]) as the first representatives of heterobimetallic group 1, Ba species of low nuclearity. The compounds display a significant degree of metal-arene interaction, believed to be a key factor in stabilizing these highly reactive species. Obtained by solid-state direct metalation, the target compounds are available without further work-up.

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}∞

“…In an attempt to expand this work to combinations of two alkali metals, identical reaction conditions were utilized to those used previously [1][2][3]. In analogy to prior work, a distinct sensitivity toward solvents was detected; the use of polar THF has previously resulted in the isolation of homometallic species [2].…”

“…This route had been used successfully to prepare aryloxide based heterobimetallic species containing combinations of alkali-alkaline earth metals [1][2][3], two different alkaline earth metals [3], and alkali-lanthanide metal combinations [3,4,11].…”

“…The low formal coordination number of three requires the large potassium center to form extensive KÀ ÀCp interactions. A typical cutoff for these interactions is 3.5 Å [1,5], as such each potassium is involved in nine p-interactions (see Figure 2); five in a Z 2 :Z 3 bonding mode from one ligand and four (Z 2 :Z 2 ) from the next one in the chain, with an average KÀ ÀCp distance of 3.02 Å . The propensity for metalÀ ÀCp interactions is also evident in the rubidium congener [Rb(Odpp)] ?…”

“…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.…”