The first strontium hydride complex has been obtained by simply treating Sr[N(SiMe ) ] with PhSiH in the presence of PMDTA. The Sr complex Sr H [N(SiMe ) ] ⋅(PMDTA) crystallizes as an "inverse cryptand": an interstitial H is surrounded by a Sr H cage decorated with amide and PMDTA ligands. The analogous Ca complex could also be obtained and both retain their solid-state structures in solution: H NMR spectra in C D show two doublets and one nonet (4:4:1). Up to 90 °C, no coalescence is observed. The Ca cluster was investigated by DFT calculations and shows atypically low charges on Ca (+1.14) and H (-0.59) which signifies an unexpectedly low ionicity. AIM analysis shows hydride⋅⋅⋅hydride bond paths with considerable electron densities in the bond critical point. The clusters thermally decompose into larger, undefined, metal hydride aggregates.

The highly sterically encumbered chelating β-diketiminate ligand, [HC{C(Me)N(2,6-CHPh2-4-MeC6H2)}2](-), (Ar)L(-), has been used to prepare a series of heteroleptic three-coordinate magnesium complexes. Both the bis(imine) and imine-enamine tautomers of the ligand precursor, (Ar)LH, as well as the diethyl ether adduct of the bromide complex [(Ar)LMgBr(OEt2)], the monomeric methyl complex [(Ar)LMgMe], the THF-solvated and unsolvated n-butylmagnesium complexes [(Ar)LMg(n)Bu(THF)] and [(Ar)LMg(n)Bu], and the 1-hexynyl analogue [(Ar)LMgC≡C(n)Bu] have been crystallographically characterized. Both n-butylmagnesium complexes showed remarkable stability in air, both in the solid state and in solution. Single crystals of the highly sensitive magnesium hydride, [(Ar)LMgH], underwent partial hydrolysis by solid-state water diffusion to the isostructural hydroxide compound [(Ar)LMgOH].

Reaction of Ba[N(SiMe ) ] with PhSiH in toluene gave simple access to the unique Ba hydride cluster Ba H [N(SiMe ) ] that can be described as a square pyramid spanned by five Ba ions with two flanking BaH[N(SiMe ) ] units. This heptanuclear cluster is well soluble in aromatic solvents, and the hydride H NMR signals and coupling pattern suggests that the structure is stable in solution. At 95 °C, no coalescence of hydride signals is observed but the cluster slowly decomposes to undefined barium hydride species. The complex Ba H [N(SiMe ) ] is a very strong reducing agent that already at room temperature reacts with Me SiCH=CH , norbornadiene, and ethylene. The highly reactive alkyl barium intermediates cannot be observed and deprotonate the (Me Si) N ion, as confirmed by the crystal structure of Ba H [N(SiMe ) ] [(Me Si)(Me SiCH )N] .

While magnesium hydride complexes are generally stabilized by hard, bulky N-donor ligands, softer ligands with a broad variety of coordination modes are shown to efficiently adapt themselves to the large variety of Mg centers in a growing magnesium hydride cluster. A P,N-chelating ligand is introduced that displays coordination modes between that of enamide, aza-allyl, and phosphinomethanide. Slight changes in the ligand bite angle have dramatic consequences for the structure type. The hitherto largest neutral magnesium hydride clusters are isolated either in a nonanuclear sheet-structure (brucite-type) or a dodecanuclear ring structure.

The first examples of magnesium acyls, [(Nacnac)Mg{μ-C(Ph)O}(μ-OR)Mg(Nacnac)] (R=Me, tBu or Ph; Nacnac=[HC(MeCNAr) ] ; Ar=C H Me -2,4,6 ( Nacnac), C H Et -2,6 ( Nacnac), C H iPr -2,6 ( Nacnac)), have been prepared by reductive cleavage of a series of esters using dimeric magnesium(I) reducing agents, [{(Nacnac)Mg} ]. Crystallographic studies reveal the complexes to be dimeric, being bridged by both phenyl-acyl and alkoxide/aryloxide fragments. The crystal structures, combined with results of spectroscopic and computational studies suggest that the nature of the acyl ligands within these complexes should be viewed as lying somewhere between anionic umpolung acyl and oxo-carbene. However, reactions of the acyl complexes with a variety of organic electrophiles did not provide evidence of umpolung acyl reactivity. A number of attempts to prepare alkoxide free magnesium acyls were carried out, and while these were unsuccessful, they did lead to unusual products, the crystallographic and spectroscopic details of which are discussed.