Miguel-Ángel Muñoz-Hernández

Tetrametallic Group 13 ‘Mitsubishi’ Molecules

Abstract Under fairly disparate conditions tetrametallic aluminum complexes can be isolated that feature a central six-coordinate aluminum connected by bridging heteroatoms to three peripheral four-coordinate aluminum atoms. Based upon their striking resemblance to the Mitsubishi emblem these molecules will be given the name ‘Mitsubishi™’ [1] . This review will discuss the formation of these compounds and will seek to establish the guiding principles under which additional ‘Mitsubishi™’ compounds may be formed. The impact of these compounds on the formation of solid-state materials, particularly aluminum oxide, will be briefly discussed.

Inorganic rings with group 13 organometallics and iminodiphosphinechalcogenides

Herein we report the synthesis and characterization of the organometallic complexes [R 2 Al{(SePPh 2 ) 2 N}] (R=Me ( 1 ), Et ( 2 ), i Bu ( 3 )) and [Et 2 Ga{(SePPh 2 ) 2 N}] ( 4 ) which were obtained through alkane elimination reactions. The compounds were characterized by physical (m.p.); chemical (C, H, analysis), and spectroscopic techniques (multinuclear NMR and IR). In addition, the crystal structure of 4 was obtained by single crystal X-ray diffraction. The molecular structure of 4 reveals a metallacycle with a diethylgallium fragment coordinated symmetrically to the imidophosphinoselenate ligand in a distorted tetrahedral environment.

Calix[4]arenes of aluminum and gallium with benzimidazolyl ligands: steric control of the conformation via substitution on the ligand.

Complexes [bzimAlR(2)](4) [bzim = benzimidazolate; R = Et (2), (i)Bu (3)], [mbzimAlR(2)](4) [mbzim = 2-methylbenzimidazolate; R = Et (6), (i)Bu (7)], [dmbzimAlR(2)](4) [dmbzim = 5,6-dimethylbenzimidazolate; R = Me (9), Et (10), (i)Bu (11)], and [tmbzimAlR(2)](4) [tmbzim = 2,5,6-trimethylbenzimidazolate; R = Me (12), Et (13), (i)Bu (14)] have been prepared via alkane elimination and coordinative self-assembly upon the reaction of benzimidazole ligands with aluminum alkyls in benzene, toluene, or xylene. Characterization of the complexes was achieved by spectroscopic methods, microanalysis, and X-ray crystallography of 2, 7, 10, 11, 13, and 14. The complexes reported herein and the aluminum and gallium analogues 1, 4, 5, and 8 reported in a previous paper (1) are predominantly tetranuclear aggregates related to calix[4]arenes in which the benzimidazolyl ligands bind two metal atoms in a η(1):η(1) fashion. X-ray crystallography demonstrates that modulation of the conformation adopted by these metallacalix[4]arenes is achieved by proper substitution on the C atom at the 2 position of the benzimidazolyl ligand. An H substituent for 1, 2, 4, 10, and 11 favors a chair conformation with a small cavity and approximate C(2h) symmetry, while a CH(3) substituent for 5, 7, 8, 13, and 14 introduces enough repulsion to switch the conformation to a 1,3-alternate or double cone with a concomitant larger cavity and approximate C(2v) symmetry.

Aluminium complexes derived from tridentate thioetherbis(phenolate) ligands and their activity in Diels–Alder catalysis

Organoaluminium(III) thioetherbis(phenolate) complexes derived from 2,2-thiobis(4,6-diterbuthylphenolate) (Stdiol) and 2,2-thiobis(4,6-dimethylphenolate) (Smdiol) were prepared by reaction of AlMe3 with the diol proligands LH2 (SmdiolH2, StdiolH2). Monomeric complexes of general formulae [LAlR(L)] (L = Stdiol, R = Me, L = THF (1); L = Stdiol, R = Me, L = Et2O (2); L = Stdiol, R = iBu, L = THF) (3); L = Smdiol, R = Me, L = THF (4); L = Smdiol, R = iBu, L = THF (5)) and [LAlCl(THF)] (L = Stdiol (6); L = Smdiol (7)) were obtained when the reactions were performed in THF or Et2O in hexane or toluene, species of formulae [(L2Al)AlR2] (L = Stdiol, R = Me (8); L = Stdiol, R = iBu (9); L = Smdiol, R = Me (10)) were formed as evidenced by spectroscopic methods. Crystals suitable for X-ray diffraction studies were obtained for 2, 3, 4, 6, 8, 9 and 10. In these cases the sulfur atom coordinates to the aluminium center with Al-S bond lengths between 2.43-2.75 A adopting boat-boat conformations. Compounds 1, 3, 4, and 8 were tested in the catalytic Diels-Alder cycloaddition reaction between methacrolein and cyclopentadiene showing excellent regioselectivities with good conversion yields.

Examination of dibenzyl aluminum and gallium azides as potential precursors to AlN and GaN

Abstract This publication summarizes our attempts to prepare precursor molecules of formula Bn2MN3-THF [where Bn=benzyl, M=Ga (3) and Al (8)] and to use them in the low-temperature synthesis of AlN and GaN. Compound 3 was prepared from Bn2GaCl-THF (2) and Me3SiN3. Compound 8 was obtained by a different route which requires the combination of Cl2AlN3 and BnMgCl in toluene. During the course of this work two new amides, [Bn2AlNMe2]2 (4) and Bn2AlN(SiMe3)2-THF (5) were prepared and structurally characterized by X-ray crystallography.

Chelated aluminum alkoxides

The present contribution will demonstrate that monomeric alkoxide compounds can be formed by the use of the Salen(tBu) ligand. These alkoxides, LAlOR (with L=Salen (tBu), R=Me (1), Salomphen(tBu), R=Me (3) and L=Salen(tBu), R=Et (4)) feature five-coordinate monomeric aluminum (Salen(tBu)=N,N′-ethylenebis(3,5-di-tert-butylsalicylideneimine) and Salomphen(tBu)=N,N′-(4,5-di-methyl)phenylenenebis(3,5-di-tert-butylsalicylideneimine). Crystallization of 1 from MeOH affords the six-coordinate complex, Salen(tBu)AlOMe(MeOH) (2). The manner in which these compounds may be obtained, as well as the structures of 2 and 4 will be described

Conformational trends in arsocane dithiophosphinates X(CH2CH2S)2AsS2PR2(X = O or S; R = Me, Et or Ph)

Six arsocane diorganodithiophosphinates X(CH2CH2S)2AsS2PR2(X = O or S; R = Me, Et or Ph) have been prepared in CH2Cl2 or benzene from X(CH2CH2S)2AsCl (X = O or S) and the corresponding sodium or ammonium dithiophosphinates. The compounds were characterised by IR, mass and 1H, 13C and 31P NMR spectroscopy. The single-crystal structures of O(CH2CH2S)2AsS2PPh2 and S(CH2CH2S)2AsS2PPh2 were determined. Both show an endocyclic, transannular As ⋯ X interaction and an exocyclic As ⋯ S secondary interaction. The co-ordination geometry can be described as trigonal bipyramidal with a face-capping intramolecular As ⋯ S secondary bonding. The oxa derivative is the first example of an arsocane of the type X(CH2CH2S)2AsY with a chair–chair conformation, while the thia derivative, as with other thiaarsocanes, shows a boat–chair conformation.

Syntheses and reactions of tetrazole-group 13 complexes

Abstract The combination of 5-phenyl-1-H-tetrazole (tet) with A1R3 in stoichiometries of 1–3 leads to the compounds [(tet)A1R2]n R = Me (1), Et (2), iBu (3), [(tet)2A1Me]n (4), and [(tet)3Al]n (5). The addition of pyridine to 1 leads to a soluble compound with the formulation, [(tet)A1Me2-pyridine]n (6). Likewise the addition of AlMe3 to 1 and 4 leads to the products [(tet)AlMe2-AlMe3]2 (7) and [(tet)2AlMe-AlMe3]n (8). The compounds were characterized by standard techniques and, in the case of 7 by X-ray crystallography. Compounds 1, 4 and 5 were examined (unsuccessfully) as potential unimolecular precursors to aluminum nitride.

Synthesis and characterization of aluminum complexes incorporating Schiff base ligands derived from pyrrole-2-carboxaldehyde

The reaction of 1,2-Ethylendiamine-N,N′-bis(1H-pyrrol-2-yl)methylene (L1H), 1,2-benzenediamine-N,N′-bis(1Hpyrrol-2-yl)methylene (L2H) and 3,4-Dimethyl-1,2-benzenediamine-N,N′-bis(1 H-pyrrol-2-yl)methylene (L3H) with one equivalent of AlR2R′ (R = alkyl, R′ = alkyl, Cl) in toluene afforded the monometallic complexes [LAlR′] (1–12). All the complexes were characterized by analytical and spectroscopic methods. Compounds 1, 3, 4, 6, 7, and 11 were characterized bya singlecrystal X-ray structural analyses. Due to the rigidity imposed by the ligand, 1, 3 and 4, with an ethylene “backbone” connecting the two nitrogens, adopt a severely distorted tbp geometry (av. = 0.68). On the other hand 6, 7 and 11, with a phenylene backbone, adopt an intermediate tbp-sqp geometry (av. = 0.43). The study of the X-ray crystal structures suggests that, like group 13 Salen complexes, flexible bridges between the two imine groups favor a tbp geometry while more rigid backbones, like phenylene rings, lead to an intermediate sqp and tbp geometry. Based on the geometrical parameter for previously reported aluminum complexes with Schiff base ligands and those presented herein, it is possible to propose that upon the coordination geometries of five coordinated aluminum complexes are less tbp distorted ( ≈ 1) the catalytic activity on ROP increases.

Unusual dicationic trimetallic aluminum chelates

Abstract The bimetallic compounds, L(AlMeCl)2 with L=Salpen(tBu) (N,N′-1,3-propylenenebis(3,5-di-tert-butylsalicylideneimine), Salben(tBu) (N,N′-1,4-butylenebis(3,5-di-tert-butylsalicylideneimine)) and Salhen(tBu) (N,N′-1,6 hexylenebis(3,5-di-tert-butylsalicylideneimine)) form the unusual trimetallic dicationic complexes, {[Salpen(tBu)∗]2(AlCl)3]}2+[GaCl4]−[GaMe2Cl2]− (1), {[Salben( t Bu) ∗ ] 2 (AlCl) 3 ]} 2+ [GaCl 4 ] − [GaMe 2 Cl 2 ] − (2) and {[Salhen( t Bu) ∗ ] 2 (AlCl) 3 ]} 2+ [GaCl 4 ] − [GaMe2Cl2]− (3) when combined with GaCl3 in toluene. In their formation, the ligands of the compounds undergo a unique dealkylation reaction to lose one tBu group from each ligand (marked with an asterisk). These compounds are a new and unique class of aluminum cations. The compounds were characterized by Mp, analyses, IR, 1H NMR, and in the case of 1 and 2, by single-crystal X-ray diffractometry.