Self‐Assembly of Magnesium Hydride Clusters Driven by Chameleon‐Type Ligands

Abstract

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.

A Molecular Barium Hydrido Complex Stabilized by a Super‐Bulky Hydrotris(pyrazolyl)borate Ligand

“…In contrast to the side-on bond fashion in [(NCN)YH(THF)] 2 (PhCHÀCCÀCHPh), [20] the PhCHÀC CÀCHPh unit in complex 4 bonds via bridging h 5 -interactions to each barium center. (4). Complex 2 was found to mediate the hydrogenation and coupling of carbon monoxide with exclusive formation of aplanar cis-ethenediolate.Reaction of complex 2 with one equivalent of 1,4-diphenyl-1,3-butadiyne allowed the isolation and structural characterization of barium 1,4-diphenyl-2-butyne-1,4-diyl complex 4,r esulting from the double 2,1-addition of hydrides into CCt riple bonds and isomerization.…”

“…[3] Despite their propensity,w ell-defined molecular Group 2 metal-hydride complexes are limited, especially for the heavy alkaline-earth metals (Ca, Sr, Ba). [4] Only ah andful of ligands are known to stabilize calcium hydride complexes, including bulky bidentate ketiminate (DIPP-nacnac = (2,6i Pr 2 C 6 H 3 )NC(Me)C(H)C(Me)N(2,6-i Pr 2 C 6 H 3 )) [5] or amidinate ( R Am = {(2,6-i Pr 2 C 6 H 3 )NC(R)N(2,6-i Pr 2 C 6 H 3 )}, R = t Bu, adamantyl) [6] ligands,a nd tetradentate macrocyclic ligands, Me 3 TACD À ((Me 3 TACD)H = 1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane) or Me 4 TACD. [4] Only ah andful of ligands are known to stabilize calcium hydride complexes, including bulky bidentate ketiminate (DIPP-nacnac = (2,6i Pr 2 C 6 H 3 )NC(Me)C(H)C(Me)N(2,6-i Pr 2 C 6 H 3 )) [5] or amidinate ( R Am = {(2,6-i Pr 2 C 6 H 3 )NC(R)N(2,6-i Pr 2 C 6 H 3 )}, R = t Bu, adamantyl) [6] ligands,a nd tetradentate macrocyclic ligands, Me 3 TACD À ((Me 3 TACD)H = 1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane) or Me 4 TACD.…”

Super‐Bulky Penta‐arylcyclopentadienyl Ligands: Isolation of the Full Range of Half‐Sandwich Heavy Alkaline‐Earth Metal Hydrides

“…On the other hand, 1-Ca exists as af ivecoordinate mono-THF adduct in the solid state.T he ORTEP drawing of 1-Ca and 1-Ba are shown in Figure 1. TheBa1 À C1 distance of 2.810(4) is slightly shorter than those in complexes Ba[CH(SiMe 3 ) 2 ] 2 (THF) 3 (2.827(3) and 2.879-(3) ) [17] and (N^N)Ba[CH(SiMe 3 ) 2 ](THF) 2 (2.840 (7) and 2.833 (7) )( N^N = iminoanilide). [18] TheB a1-Cent1 distance of 2.799 is significantly longer than those in sandwich complexes (Cp BIG ) 2 Ba (2.667 ) [15b] and (C 5 Ph 5 ) 2 Ba (2.670 ), [19] suggesting strong steric repulsion between the Cp Ar ligand and CH(SiMe 3 ) 2 group.…”

“…Molecular alkaline-earth-metal hydrides continue to receive growing interest, [1] as they are used as low-cost and non-toxic alternatives to transition-metal catalysts in various organic transformations. [2] Thel ighter magnesium hydride complexes [3] are also regarded as potential materials for hydrogen storage. [4] Among the limited number of welldefined molecular Group 2m etal-hydride complexes,m agnesium hydrides dominate with over 40 examples.…”

“…Crystal structure of 4-Sr is similar to 2-Ca except for the coordinated donor solvent. TheS r ÀHd istances (2 .26(5) and 2.28 (5) ) are significantly shorter than those in complexes [L Ad Sr(m-H)] 2 (2.38(3) and 2.43 (3) ), [7b] Sr 6 H 9 [N(SiMe 3 ) 2 ] 3 (PMDTA) 3 (2.38(4)-2.78 (8) (4) ). [7c] Hydrogenolysis of (Cp Ar )Ba[CH(SiMe 3 ) 2 ](DABCO) x , generating in situ from the reaction of (Cp Ar )Ba[CH-(SiMe 3 ) 2 ](THF) with DABCO in hexane,a fforded the corresponding barium hydrides complex [(Cp Ar )Ba(m-H)-(DABCO)] 2 (4-Ba)a st he sole barium species.Asinglet at 9.32 ppm in the 1 HNMR spectra of 4-Ba in cyclohexane-d 12 , which integrated as 1H per Cp Ar ligand, is assigned to the hydrido ligand.…”