Isomeric Al₂R₄, Mg₂R₂ Species and Oligomerisation Products: Investigation of Al–Al and Mg–Mg σ Bonding

Hunting for the Magnesium(I) Species: Formation, Structure, and Reactivity of some Donor‐Free Grignard Compounds

“…(2)] to oligomeric MgS and the tetrameric donor-free Grignard- [26,27] two tetrameric species C are formed with a structure analogous to the [Mg 4 Cl 4 ] species published earlier. [3] Thereafter two Mg 2 moieties are formed ([(MgS) 2 ] (D) and [(RMgSR) 2 ] (E)) via a redox process, and finally the products F and G, that is, a tetrameric donor-stabilized MgS and a tetrameric Grignard-like compound similar to 4, are obtained exothermically.…”

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Dedicated to Professor Dieter Fenske on the occasion of his 70th birthdayIn analogy to and as a consequence of our previous work, starting with the generation of Al I /Ga I halides [1] and ending up with the formation of metalloid aluminum and gallium clusters as intermediates between the bulk element and saltlike compounds, [2] we have been interested in investigating the monovalent state of Mg as the neighbor element of Al, and in particular thermodynamic and quantum chemical considerations. [3] However, as the generation of MgCl for example is much more difficult than the formation of AlCl, [4] we worked intensively to develop suitable experimental methods for the generation of MgCl. During this time, lowvalent Group 2 element chemistry has been developed [5] and the groups of Jones and others [6, 7] were successful in presenting first examples of molecules that contain Mg I atoms within an MgÀMg s bond stabilized by chelating ligands to each Mg center: [RMgMgR] (R = [(Ar)NC(NiPr 2 )N(Ar)] À (priso) and [{(Ar)NCMe} 2 CH] À (nacnac); Ar = 2,6-diisopropylphenyl, iPr = isopropyl).

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Stable Radicals of the Heavy p‐Block Elements

“…The odd electron occupies a bonding π molecular orbital formed by overlap of the p z orbitals on the two gallium atoms resulting in a formal bond order of 1.5 for the Ga-Ga bond. The EPR spectrum of 5b shows a 64-line signal (g = 1.9947) arising from coupling of the unpaired electron with the two inequivalent gallium centers ( 69 Ga, I = 3/2, 60.1 %; 71 Ga, I = 3/2, 30.9 %). 12a The two different hfcc values (a 1 ( 69/71 Ga) = 50/64 G and a 2 ( 69/71 Ga) = 32/41 G) could not be assigned to the twoand three-coordinate gallium atoms with certainty.…”

“…The EPR spectra of 9a-d show that the central group 13 metal atom and the NBN boron atoms have non-zero spin density values arising from polarization effects. The experimental spectra of these spirocyclic neutral radicals can, therefore, be simulated by assuming hyperfine interaction of the unpaired electron with four equivalent nitrogen centers, two boron atoms and the central group 13 element ( 27 Al, I = 5 / 2 , 100 %; 69 Ga, I = 3 / 2 , 60.1 %;71 Ga, I = 3 / 2 , 39.9 %; 113 In, I = 9 / 2 , 4.3 %;…”

Snapshots of the AlAl σ‐Bond Formation Starting from {AlR2} Units: Experimental and Computational Observations

“…[7] In addition to these extensive experimental investigations, detailed quantum chemical calculations have been performed, which were published recently in a separate contribution. [9] The main computational results are summarized in Figure 1 [9,10] with a long AlÀAl separation of approximately 350 pm and with each unpaired electron residing in a p-type singly occupied molecular orbital localized on one of the Al atoms. These triplet molecules 1 can formally undergo a spinflip procedure and a subsequent disrotatorial ring closure leading to closed-shell bicyclic molecules [RAlR 2 AlR] (2, C 2 symmetry) as thermodynamically stable species (s-bond formation).…”