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Synthetic routes to lithium, magnesium, and zinc aluminyl complexes are reported, allowing for the first structural characterization of an unsupported lithium–aluminium bond. Crystallographic and quantum‐chemical studies are consistent with the presence of a highly polar Li−Al interaction, characterized by a low bond order and relatively little charge transfer from Al to Li. Comparison with magnesium and zinc aluminyl systems reveals changes to both the M−Al bond and the (NON)Al fragment (where NON=4,5‐bis(2,6‐diisopropylanilido)‐2,7‐di‐tert‐butyl‐9,9‐dimethylxanthene), consistent with a more covalent character, with the latter complex being shown to react with CO2 via a pathway that implies that the zinc centre acts as the nucleophilic partner. [ABSTRACT FROM AUTHOR]

We present a novel approach for constructing chains of Group 14 metal atoms linked by unsupported metal–metal bonds that exploits hemilabile ligands to generate unsaturated metal sites. The formation/nature of catenated species (oligo‐dimetallynes) can be controlled by the use of (acidic/basic) "protecting groups" and through variation of the ligand scaffold. Reduction of ArNiPr2GeCl (ArNiPr2=2,6‐(iPr2NCH2)2C6H3)—featuring hemilabile NiPr2 donors—yields (ArNiPr2Ge)4 (2), which contains a tetrameric Ge4 chain. 2 represents a novel type of a linear homo‐catenated GeI compound featuring unsupported E−E bonds. Trapping experiments reveal that a key structural component is the central two‐way Ge=Ge donor‐acceptor bond: reactions with IMe4 and W(CO)5(NMe3) give the base‐ or acid‐stabilized digermynes (ArNiPr2Ge(IMe4))2 (4) and (ArNiPr2Ge{W(CO)5})2 (5), respectively. The use of smaller N‐donors leads to stronger Ge‐N interactions and quenching of catenation behaviour: reduction of ArNEt2GeCl gives the digermyne (ArNEt2Ge)2, while the unsymmetrical system ArNEt2GeGeArNiPr2 dimerizes to give tetranuclear (ArNEt2GeGeArNiPr2)2 through aggregation at the NiPr2‐ligated GeI centres. [ABSTRACT FROM AUTHOR]

The synthesis of a novel mono‐anionic phosphino‐amide ligand based on a xanthene backbone is reported, togetherr with the corresponding GaI complex, (PON)Ga (PON = 4‐(di(2,4,6‐trimethylphenyl)phosphino)‐5‐(2,6‐diisopropylanilido)‐2,7‐di‐tert‐butyl‐9,9‐dimethylxanthene). The solid‐state structure of (PON)Ga (obtained from X‐ray crystallography) reveals very weak O⋅⋅⋅Ga and P⋅⋅⋅Ga interactions, consistent with a R2NGa fragment which closely resembles those found in one‐coordinate amidogallium systems. Strong N‐to‐Ga π donation from the amido substituent is reflected in a very short N−Ga distance (1.961(2) Å), while the P⋅⋅⋅Ga contact (3.076(1) Å) is well outside the sum of the respective covalent radii. While the donor properties of the PON ligand towards GaI are highly unsymmetrical, oxidation to GaIII leads to much stronger coordination of the pendant phosphine as shown by P−Ga distances which are up to 20 % shorter. From a steric perspective, the PON ligand is shown to be significantly bulkier than related β‐diketiminate systems, a finding consistent with reactions of (PON)Ga towards O‐atom sources that proceed without oligomerization. Despite this, the enhanced P‐donor properties brought about by oxidation at gallium are not sufficient to quench the reactivity of the highly polar Ga−O unit. Instead, intramolecular benzylic C−H activation is observed across the Ga−O bond of a transient gallanone intermediate. [ABSTRACT FROM AUTHOR]