The chemistry of the p-block elements is a huge playground for fundamental and applied work.

Group 13 MI compounds often disproportionate into M0 and MIII. Here, however, we show that the reaction of the MI salt of the weakly coordinating alkoxyaluminate [GaI(C6H5F)2]+[Al(ORF)4]− (RF=C(CF3)3) with 2,2'-bipyridine (bipy) yields the paramagnetic and distorted octahedral [Ga(bipy)3]2+•{[Al(ORF)4]−}2 complex salt. While the latter appears to be a GaII compound, both, EPR and DFT investigations assign a ligand-centred [GaIII{(bipy)3}•]2+ radical dication. Surprisingly, the application of the heavier homologue [InI(C6H5F)2]+[Al(ORF)4]− leads to aggregation and formation of the homonuclear cationic triangular and rhombic [In3(bipy)6]3+, [In3(bipy)5]3+ and [In4(bipy)6]4+ metal atom clusters. Typically, such clusters are formed under strongly reductive conditions. Analysing the unexpected redox-neutral cationic cluster formation, DFT studies suggest a stepwise formation of the clusters, possibly via their triplet state and further investigations attribute the overall driving force of the reactions to the strong In−In bonds and the high lattice enthalpies of the resultant ligand stabilized [M3]3+{[Al(ORF)4]−}3 and [M4]4+{[Al(ORF)4]−}4 salts.

The scope of the univalent gallium salts [Ga-(C 6 H 5 F) 2 ] + [Al(OR F ) 4 ] − and the new completely characterized [Ga(1,3,5-Me 3 C 6 H 3 ) 2 ] + [Al(OR F ) 4 ] − (R F = C(CF 3 ) 3 ) was investigated in terms of initiating or catalyzing the synthesis of highly reactive poly(2-methylpropylene)highly reactive polyisobutylene (HR-PIB)in several solvents. A series of polymerization reactions proved the high efficiency and quality of the univalent gallium salts for the polymerization of isobutylene. The best results were obtained using very low concentrations of [Ga-(C 6 H 5 F) 2 ] + [Al(OR F ) 4 ] − (down to 0.007 mol%) while working at reaction temperatures of up to ±0 °C and in the noncarcinogenic and non-water hazardous solvent toluene. Under these conditions, HR-PIB with an α-content of terminal olefinic double bonds up to 91 mol% and a molecular weight of 1000−2000 was obtained in good yields. Upon changing [Ga(C 6 H 5 F) 2 ] + [Al(OR F ) 4 ] − for the electron richer [Ga(1,3,5-Me 3 C 6 H 3 ) 2 ] + [Al-(OR F ) 4 ] − , polymerization temperatures could be increased to +10 °C. The reactivity of the gallium(I) cations therefore seems to be tunable through ligand exchange reactions. Experimental results, density functional theory calculations, and mass spectrometric investigations point toward a coordinative polymerization mechanism. Article pubs.acs.org/Organometallics

Using [Ga(C6 H5 F)2 ](+) [Al(OR(F))4 ](-) (1) (R(F) =C(CF3)3) as starting material, we isolated bis- and tris-η(6) -coordinated gallium(I) arene complex salts of p-xylene (1,4-Me2 C6 H4), hexamethylbenzene (C6 Me6 ), diphenylethane (PhC2 H4 Ph), and m-terphenyl (1,3-Ph2 C6 H4): [Ga(1,4-Me2 C6 H4 )2.5 ](+) (2(+)), [Ga(C6 Me6 )2 ](+) (3(+)), [Ga(PhC2 H4 Ph)](+) (4(+)) and [(C6 H5 F)Ga(μ-1,3-Ph2 C6 H4)2 Ga(C6 H5 F)](2+) (5(2+)). 4(+) is the first structurally characterized ansa-like bent sandwich chelate of univalent gallium and 5(2+) the first binuclear gallium(I) complex without a Ga-Ga bond. Beyond confirming the structural findings by multinuclear NMR spectroscopic investigations and density functional calculations (RI-BP86/SV(P) level), [Ga(PhC2 H4 Ph)](+) [Al(OR(F))4](-) (4) and [(C6 H5 F)Ga(μ-1,3-Ph2 C6 H4)2 Ga(C6 H5 F)](2+) {[Al(OR(F) )4] (-)}2 (5), featuring ansa-arene ligands, were tested as catalysts for the synthesis of highly reactive polyisobutylene (HR-PIB). In comparison to the recently published 1 and the [Ga(1,3,5-Me3 C6 H3)2](+) [Al(OR(F))4](-) salt (6) (1,3,5-Me3 C6 H3 =mesitylene), 4 and 5 gave slightly reduced reactivities. This allowed for favorably increased polymerization temperatures of up to +15 °C, while yielding HR-PIB with high contents of terminal olefinic double bonds (α-contents=84-93 %), low molecular weights (Mn =1000-3000 g mol(-1)) and good monomer conversions (up to 83 % in two hours). While the chelate complexes delivered more favorable results than 1 and 6, the reaction kinetics resembled and thus concurred with the recently proposed coordinative polymerization mechanism.

Transformations of alkene and alkyne substrates relevant to p-Lewis acid catalysis have been performed using low-valent Ga(I) species for the first time. [Ga(I)(PhF) 2 ] + [Al(OR F ) 4 ] À and gallium dichloride (i. e. [Ga(I)] + [GaCl 4 ] À ) proved to be efficient catalysts for cycloisomerizations, Friedel-Crafts reactions, transfer hydrogenations, and reductive hydroarylations. Their activity is compared to more common Ga(III) complexes. This study shows that even the readily available and yet overlooked gallium dichloride salt can be a more active p-Lewis acid catalyst than gallium trichloride or other Ga(III) species.

To answer the question as to whether gallium in its oxidation state +1 favors a σ‐ or a π‐coordination of aromatic nitrogen bases, we reacted [Ga(C6H5F)2]+[Al(ORF)4]– {RF = C(CF3)} with pyrazine and 2,6‐di‐tert‐butyl‐4‐methylpyridine (DTBMP). In doing so, we obtained the first tricoordinate, nonchelated, homoleptic N‐donor complex of gallium(I): [Ga(pyrazine)3]+[Al(ORF)4]–, in which each gallium(I) cation is coordinated in a trigonal‐pyramidal fashion by three η1‐donating pyrazine ligands. Hence, the gallium(I) cations favor σ‐ over π‐coordination. Depending on the reaction conditions, and due to the bifunctionality of pyrazine, 1D coordination polymers of {[Ga(μ‐pyrazine)2(η1‐pyrazine)]+[Al(ORF)4]–}∞ were also obtained. With the sterically demanding DTBMP, which is conventionally used as a proton scavenger, the mixed complex [Ga(C6H5F)2(DTBMP)]+[Al(ORF)4]– was isolated, thus proving incorrect the perception of DTBMP being “non‐nucleophilic”. The structural findings were confirmed by multinuclear NMR investigations and density functional performed at the RI‐BP86/SV(P) level.

… Similar to a Japanese bento box, gallium(I) chemistry offers a wide range of "different tastes" regarding fundamental and applied science. In their Full Paper on page 157 ff., I. Krossing et al. describe the ansa-arene complexes [Ga(PhC 2 H 4 Ph) 2 ] + and [(C 6 H 5 F)Ga(m-1,3-Ph 2 C 6 H 4) 2 Ga(C 6 H 5 F)] 2 + , featuring the weakly coordinating [Al(OC(CF 3) 3) 4 ] À anion, that not only deliver interesting insights into the bonding nature of univalent gallium, but also are highly efficient catalysts for the polymerization of isobutylene. WCA = weakly-coordinating anions. PIB = polyisobutylene.

Using [Ga(C H F) ] [Al(OR ) ] (1) (R =C(CF ) ) as starting material, we isolated bis- and tris-η -coordinated gallium(I) arene complex salts of p-xylene (1,4-Me C H ), hexamethylbenzene (C Me ), diphenylethane (PhC H Ph), and m-terphenyl (1,3-Ph C H ): [Ga(1,4-Me C H ) ] (2 ), [Ga(C Me ) ] (3 ), [Ga(PhC H Ph)] (4 ) and [(C H F)Ga(μ-1,3-Ph C H ) Ga(C H F)] (5 ). 4 is the first structurally characterized ansa-like bent sandwich chelate of univalent gallium and 5 the first binuclear gallium(I) complex without a GaGa bond. Beyond confirming the structural findings by multinuclear NMR spectroscopic investigations and density functional calculations (RI-BP86/SV(P) level), [Ga(PhC H Ph)] [Al(OR ) ] (4) and [(C H F)Ga(μ-1,3-Ph C H ) Ga(C H F)] {[Al(OR ) ] } (5), featuring ansa-arene ligands, were tested as catalysts for the synthesis of highly reactive polyisobutylene (HR-PIB). In comparison to the recently published 1 and the [Ga(1,3,5-Me C H ) ] [Al(OR ) ] salt (6) (1,3,5-Me C H =mesitylene), 4 and 5 gave slightly reduced reactivities. This allowed for favorably increased polymerization temperatures of up to +15 °C, while yielding HR-PIB with high contents of terminal olefinic double bonds (α-contents=84-93 %), low molecular weights (M =1000-3000 g mol ) and good monomer conversions (up to 83 % in two hours). While the chelate complexes delivered more favorable results than 1 and 6, the reaction kinetics resembled and thus concurred with the recently proposed coordinative polymerization mechanism.