Gas Phase Complexes MX₃·4,4‘Bpy·M‘X₃ (M,M‘ = Al, Ga; X = Cl, Br):  Experiment and Theory

Abstract

Donor-acceptor (DA) complexes MX 3 ‚LL‚M′X 3 (M, M′ ) Al, Ga; X ) Cl, Br; LL ) 4,4′-bipyridyl) have been theoretically investigated at the B3LYP/pVDZ level of theory. Addition of the first molecule of MX 3 to 4,4′-bipyridyl has a similar exothermicity compared to complexes with the monodentate donor pyridine. Addition of the second molecule of MX 3 is significantly (by about 15 kJ mol -1 ) less exothermic. Nevertheless all 2:1 complexes (including heteroacceptor) are predicted to be stable in the vapor phase up to 660, 760, 830 and 920 K for GaBr 3 , GaCl 3 , AlBr 3 , and AlCl 3 , respectively. Four homoacceptor MX 3 ‚4,4′bpy‚MX 3 complexes have been synthesized for the first time, and their existence in the vapor phase has been proven by mass spectrometry. The theoretically predicted order of the complex stability AlCl 3 > AlBr 3 > GaCl 3 > GaBr 3 correlates well with the experimental observations of M 2 X 5 bpy + ion abundances in the mass spectra. The results obtained show for the first time that the synthesis of the gas-phase stable heteroacceptor complexes is feasible, which opens the prospect for their future use as single-source precursors to the stoichiometrycontrolled synthesis of 13-15 alloys.

Ring and cage compounds from complexes of group 13 metal halides with ethylenediamine: Experiment and theory

“…Among potential SSP, 13-15 ring and cage compounds and donor acceptor (DA) complexes of group 13 metal halides MX 3 with nitrogen containing polydentate ligands attracted some attention [2]. Existence of gaseous complexes of the type MX 3 AE L-L AE MX 3 (where bidentate donor ligand LL is 4,4 0 -bipyridine [3], tetramethylethylenediamine [4] and pyrazine [5]) was experimentally confirmed by mass spectrometry and tensimetry methods. Ethylenediamine NH 2 CH 2 CH 2 NH 2 (en) is a well known chelating ligand, which with group 13 metal trications forms ionic complexes, for example [Ga(en) 3 ]Cl 3 [6].…”

“…Methane elimination and formation of dimeric amido complexes was evidenced in reaction of Al(CH 3 ) 3 with NH 2 CH 2 (o-C 5 H 4 N) in hexane at 0°C [9]. It is expected, that thermolysis of MX 3 recently [10], however, there is a little information about their thermal stability in the gas phase. We suppose that substitution of the organometallic acceptors by group 13 metal halides will allow stabilization of the ring and cage compounds in the gas phase.…”

Thermodynamics of the Decomposition Processes of Donor–Acceptor Complexes MX3⋅en⋅MX3 and MX3⋅en

“…The existence of gaseous MX 3 ·(4,4'-bipy)·MX 3 complexes with 4,4'-bipyridine was theoretically predicted and experimentally confirmed. [3] Herein, we theoretically examine the structures and stability of molecular complexes of Group 13 metal halides with ethylenediamine (en). En is a well-known chelating ligand, which with Group 13 metal halides forms ionic complexes of the type [M(en) 3 ]X 3 .…”

“…[3] Herein, we theoretically examine the structures and stability of molecular complexes of Group 13 metal halides with ethylenediamine (en). En is a well-known chelating ligand, which with Group 13 metal halides forms ionic complexes of the type [M(en) 3 ]X 3 . [4] However, besides these ionic complexes where en acts as a chelating ligand towards the Group 13 metal trication, there is a possibility of forming molecular DA complexes in which en has nonchelating coordination.…”

“…Two such complexes with MX 3 /en ratios of 1:1 (X 3 M·NH 2 C 2 H 4 NH 2 ) and 2:1 (X 3 M·NH 2 C 2 H 4 NH 2 ·MX 3 ) are theoretically possible. These molecular DA complexes are expected to be volatile compounds in contrast to the low-volatile ionic species [M(en) 3 ]X 3 with strong crystal lattices, and complexes of 2:1 composition with two different metal centers attached to the nonchelating en ligand are promising single-source precursors towards Group 13-15 composites.…”