The hydrogallation of CN double bonds—reactions of GaH3·NMe2Et with tetramethyl-2,3-diazabutadiene

Syntheses, Characterization, and Multifaceted Coordination Chemistry of Hydrazonido Titanium Complexes

The reaction of hydrazones with bis(π-η5:σ-η1-pentafulvene)titanium complexes leads to both hydrazonido and hydrazido complexes depending on the interaction of the hydrazone with the fulvene ligand of the metal complex. The molecular structures mostly reveal κ2N,N side-on coordination of the hydrazonido ligand due to the deprotonation of the N-H bond by one of the fulvene moieties. Instead of deprotonation, the reaction of the bis(adamantylidene fulvene)titanium complexes with cinnamon aldehyde phenylhydrazone leads to κ1N coordination. By using donating groups in the backbone of the hydrazone ligands, there are exceptions to this coordination mode due to the insertion of the C═N double bond into the Ti-Cexo bond of the pentafulvene moiety. Using 2-pyridinecarboxaldehyde phenylhydrazone, a formal κ3N,N,N ligand system is formed by the coordination of the pyridine nitrogen atom to the metal center via consecutive N-H deprotonation and insertion. Finally, the use of salicylaldehyde phenylhydrazone ultimately produces a complex with the κ3N,N,O coordination mode by double deprotonation of the hydrazone N-H and O-H functions. Because of its slow conversion to the final product, the intermediate was isolated as an insertion product with consecutive O-H deprotonation, showing a κ2N,O coordination mode of the hydrazido ligand.

Molecular Main Group Metal Hydrides

This review serves to document advances in the synthesis, versatile bonding, and reactivity of molecular main group metal hydrides within Groups 1, 2, and 12-16. Particular attention will be given to the emerging use of said hydrides in the rapidly expanding field of Main Group element-mediated catalysis. While this review is comprehensive in nature, focus will be given to research appearing in the open literature since 2001.

Hydrogallation of Alkynes with H−GaCl2: Formation of Organoelement Dichlorogallium Compounds Potentially Applicable as Chelating Lewis Acids

Treatment of trimethylsilylethynylbenzenes C6H6-x(C[TRIPLE BOND]C-SiMe3)x(x=1-3) with the hydridodichlorogallium compound H-GaCl2 afforded, almost quantitatively, the alkenylphenyl compounds C6H6-x[C(H)C(SiMe3)-GaCl2]x[x=1 (6), 2 (7), and 3 (8)] by hydrogallation. Only compound 6 was readily soluble in n-hexane; it formed dimers via Ga-Cl bridges. The bisalkenyl compound 7 was only sparingly soluble; its molecular structure consisted of a singular dimeric formula unit with a cyclophane-type constitution and two bridging Ga 2Cl 2 heterocycles. The overall structure may be described by a molecular box formed by a large macrocycle comprising 22 Ga, C, and Cl atoms. Compound 8 proved to be insoluble in hydrocarbon solvents. Its molecular structure could not be detected. Extraction of the solid raw products of 7 and 8 with diethyl ether yielded small quantities of the ether adducts C6H6-x[C(H)C(SiMe3)-GaCl2(OEt2)]x(x=2, 3) [7(OEt2)2 and 8(OEt2)3], both of which are monomeric because of the coordinative saturation of their gallium atoms. The tetraalkyne 1,2,4,5-tetrakis(trimethylsilylethynyl)benzene gave a different reaction course. Complete hydrogallation resulted in the release of 2 equiv of GaCl3, and neighboring alkenyl groups of the product 9 were connected by GaCl bridges to form seven-membered heterocycles and an overall tricyclic compound. Compound 9 was characterized as a diethyl ether adduct.

The reactions of dialkylgallium hydrides with tert-butylethynylbenzenes—a systematic investigation into the course of hydrogallation reactions

The reactions of bis- and tris(tert-butylethynyl)benzenes with dialkylgallium hydrides afforded two different types of products. 1,4-Di(tert-butylethynyl)benzene and dialkylgallium hydrides R(2)GaH bearing relatively small substituents (R = Et, nPr) gave the expected addition products with each C triple bond C triple bond inserted into a Ga-H bond. The intact GaR(2) groups are attached to those carbon atoms which are in alpha-position to the benzene rings, and intermolecular Ga-C interactions led to the formation of one-dimensional coordination polymers. In contrast secondary reactions with the release of the corresponding trialkylgallium derivatives GaR(3) (R = Et, nPr, iPr, CH(2)tBu, tBu) were observed for all hydrogallation reactions involving the trisalkyne 1,3,5-tris(tert-butylethynyl)benzene. A similar reaction was observed upon treatment of the 1,4-bisalkyne with a dialkylgallium hydride bearing a relatively bulky substituent (R = neopentyl). Cyclophane type molecules are formed in all these cases with two or three gallium atoms in the bridging positions between both benzene rings.

1,1,3,3-Tetramethylguanidine–gallane, (Me2N)2CN(H)·GaH3: an unusually strongly bound gallane adduct

The novel adduct 1,1,3,3-tetramethylguanidine-gallane, (Me2N)2CN(H).GaH3, has been prepared by the reaction of [(Me2N)2CNH2]+Cl- with LiGaH4 in Et2O solution. Its spectroscopic properties indicate a monomeric species with an unusually strong coordinate link between the imido function and GaH3, an inference confirmed by the crystal structure at 150 K which also reveals significant secondary interactions through non-classical N-H...H-Ga bridges. Despite the intrinsic strength of the Ga-N bond, however, vaporisation at ca. 310 K occurs with partial dissociation, and decomposition via more than one pathway proceeds at temperatures >330-350 K to give a variety of products, including the free base, Me2NH, H2, and a novel gallium-nitrogen compound composed of a Ga4N4 cubane-like core bridged on three edges by -N{C(NMe2)2}GaH2- units.