Encapsulation of hydride by molecular main group metal clusters: manipulating the source and coordination sphere of the interstitial ion

Abstract

The sequential treatment of Lewis acids with N,N'-bidentate ligands and thereafter with ButLi has afforded a series of hydride-encapsulating alkali metal polyhedra. While the use of Me3Al in conjunction with Ph(2-C5H4N)NH gives Ph(2-C5H4N)NAlMe2 and this reacts with MeLi in thf to yield the simple 'ate complex Ph(2-C5H4N)NAlMe3Li.thf, the employment of an organolithium substrate capable of beta-hydride elimination redirects the reaction significantly. Whereas the use of ButLi has previously yielded a main group interstitial hydride in which H- exhibits micro6-coordination, it is shown here that variability in the coordination sphere of the encapsulated hydride may be induced by manipulation of the organic ligand. Reaction of (c-C6H11)(2-C5H4N)NH with Me3Al/ButLi yields [{(c-C6H11)(2-C5H4N)N}6HLi8]+[(But2AlMe2)2Li]-, which is best viewed as incorporating only linear di-coordination of the hydride ion. The guanidine 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hppH) in conjunction with Me2Zn/ButLi yields the micro8-hydride [(hpp)6HLi8]+[But3Zn]-.0.5PhMe. Formation of the micro8-hydride [(hpp)6HLi8]+[ButBEt3]- is revealed by employment of the system Et3B/ButLi. A new and potentially versatile route to interstitial hydrides of this class is revealed by synthesis of the mixed borohydride-lithium hydride species [(hpp)6HLi8]+[Et3BH]- and [(hpp)6HLi8]+[(Et3B)2H]- through the direct combination of hppLi with Et3BHLi.

Reactivity of boryllithium with AlMe3, AlEt3, and GaMe3, including the synthesis of a lanthanum heterogallate complex

“…11 Another Al(μ-Me) 2 Li motif was obtained by the reaction of amidoalane Ph(2-C 5 H 4 N)NAlMe 2 with MeLi in THF under formation of complex Ph(2-C 5 H 4 N)NAlMe 3 Li•THF. 12 1-Alkynylaluminum ate complexes of lithium are also known and their syntheses have been achieved from AlR 3 (R = Me, Et, iBu, n-C 8 H 17 ) and 1-lithio-1-alkynes. The complexes were reported to react with electrophiles, e.g., PhSCl, under rearrangement to tetrasubstituted olefins.…”

“…H NMR (cyclohexane-d12 , 400 MHz, 26 °C): δ = 7.15 (t, 6 H, 3 J = 7.5 Hz, p-C 6 H 3 -iPr 2 ), 7.07(d, 12 H, m-C 6 H 3 -iPr 2 , 3 J = 7.4 Hz), 6.23 (s, 6 H, NCH), 3.05 (sep, 12 H, 3 J = 7.0 Hz, CHMe 2 ), 1.11 (d, 36 H, 3 J = 6.4 Hz, CHMe 2 ), 1.08(d, 36 H, 3 J = 7.0 Hz, CHMe 2 ), −0.67 (s, 27 H, GaMe 3 ) ppm 13. C { 1 H} NMR (cyclohexane-d 12 , 126 MHz, 10 °C): δ = 146.4 (o-C 6 H 3 -iPr 2 ), 141.6 (i-C 6 H 3 -iPr 2 ) (very weak), 127.7 ( p-C 6 H 3 -iPr 2 ), 123.5 (m-C 6 H 3 -iPr 2 ), 121.5 (NCH), 28.9 (CHMe 2 ), 24.8 (CHMe 2 ),23.8 …”

Alkali and alkaline earth metals

“…The mixed borohydride/lithium hydride species [(hpp) 6 HLi 8 ] + [Et 3 BH] À and [(hpp) 6 HLi 8 ] + [(Et 3 B) 2 H] À were also synthesised through the direct combination of hppLi with Et 3 BHLi. 40 Reactions mediated by lithium diisopropylamide (LDA) with added hexamethylphosphoramide (HMPA) have been described. The Nisopropylimine of cyclohexanone lithiates via monomer-based pathways while conjugate addition of LDA/HMPA to an unsaturated ester proceeds via di and tetra-HMPA-solvated dimers.…”

A pyrazolate-stabilized sodium hydride complex

“…For the alkali metals, only well-defined molecular complexes of LiH are known. 3 These include monohydride complexes with a central hydride ion in a cage compound, [4][5][6] and larger aggregates with central (LiH) 4 core, 7 or up to nanometer-sized LiH clusters 4,8,9 such as [(pz) 12 Li 37 H 25 ] and [(pz) 12 Li 37 (thf) 2 H 26 ] À (pz = 3,5-di-tertbutylpyrazolate). 4 These soluble and molecular complexes generally show different and higher reactivity compared with their parent ionic solids.…”