Arylcalcium Hydrides as Precursors to Alkoxides and Aryloxides of Calcium

Abstract

Calcium atoms react with +I-substituted benzene derivatives under cocondensation conditions to yield arylcalcium hydrides. With toluene, tert-butylbenzene, and trimethyl(phenyl)silane the reaction showed no selectivity for C−H activation, resulting in the formation of each of the three possible isomers, while with m-xylene the reaction resulted in selective activation of the bond meta to the CH 3 groups. Treatment of (tert-butylphenyl)calcium hydride with di-and trisubstituted phenols such as 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, and 2,4,6-tri-tert-butylphenol resulted in the formation of calcium aryloxides in yields Ͼ 95%.[Ca(2,4,6-tBu 3 C 6 H 2 O) 2 (THF) 3 ] crystallises from a THF solution as a distorted trigonal bipyramid, with two THF ligands in the trans-axial positions and the third THF ligand and both aryloxide groups in equatorial positions. The Ca−O Aryl bond

Heavy Grignard Reagents: Challenges and Possibilities of Aryl Alkaline Earth Metal Compounds

“…[22] The co-condensation of calcium with benzene and alkylbenzenes yielded the insertion products, namely the arylcalcium hydrides. [23,24] However, neither NMR data nor structural parameters were reported. [25] Only very recently, Harder published the first molecular structure of a heteroleptic organocalcium hydride.…”

Monoanionic N,P,S‐Janus Head Tripods in s‐Block Metal Coordination

“…[34] The reported mean Rb-N bond length of 3.197 Å is close to the value for Rb1-N3 [3.0458(16) Å] in 3. Another compound with the composition [(tBuO) 8 Li 4 Rb 4 ] contains neither nitrogen nor phosphorus atoms, which is also the case with the other examples in the CSD. [35] Interestingly, there are two signals in the 7 Li{ 1 H} NMR spectrum of 3.…”

“…The use of benzyl calcium as a precatalysis for the hydrosilylation of 2-vinylpyridine has been studied by Souter et al [12] [a] Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstr. 4 Heterobimetallic complexes have gained ever increasing attention in preparative chemistry, [9] above all for use in deprotonation reactions. Usually, lithium organic reagents like BuLi or LDA are used for such purposes.…”

“…[3] These aryl alkaline earth metal halides and hydrides [4] show increased reactivity in metallation reactions, [5] metathesis [6] and addition reactions [7] in comparison to their magnesium counterparts. Organocalcium compounds are used as initiators for ring-opening polymerisations of cyclic esters.…”

Synthesis and characterization of rare examples of stable potassium and arylcalcium triethylboranate complexes

“…Harder and co-workers demonstrated that R-Ca-H is a valuable synthon [5] for the hydrogenation of alkenes [6], an intermediate during hydrosilylation of ketones [7], and reacts also as a strong reducing reagent [8]. Phenylcalcium hydride (R = Ph) was prepared via a cocondensation reaction of calcium with benzene yielding extremely reactive PhCaH [9,10]. Stability of an organylcalcium hydride can be enhanced if R represents an extremely bulky β-diketiminate ligand which is able to prevent the precipitation of insoluble CaH 2 via a dismutation reaction [11].…”