Unexpected Reactivity and Coordination in Gallium(III) and Indium(III) Chloride Complexes With Geometrically Constrained Thio- and Selenoether Ligands

Abstract

Reaction of GaCl(3) with 1 mol equiv of [14]aneS(4) in anhydrous CH(2)Cl(2) gives the exocyclic chain polymer [GaCl(3)([14]aneS(4))] (1) whose structure confirms trigonal bipyramidal coordination at Ga with a planar GaCl(3) unit. In contrast, using [16]aneS(4) and GaCl(3) or [16]aneSe(4) and MCl(3) (M = Ga or In) in either a 1:1 or a 1:2 molar ratio produces the anion-cation complexes [GaCl(2)([16]aneS(4))][GaCl(4)] (2) and [MCl(2)([16]aneSe(4))][MCl(4)] (M = Ga, 3 and M = In, 4) containing trans-octahedral cations with endocyclic macrocycle coordination. The ligand-bridged dimer [(GaCl(3))(2){o-C(6)H(4)(SMe)(2)}] (5) is formed from a 2:1 mol ratio of the constituents and contains distorted tetrahedral Ga(III). This complex is unusually reactive toward CH(2)Cl(2), which is activated toward nucleophilic attack by polarization with GaCl(3), producing the bis-sulfonium species [o-C(6)H(4)(SMeCH(2)Cl)(2)][GaCl(4)](2) (6), confirmed from a crystal structure. In contrast, the xylyl-based dithioether gives the stable [(GaCl(3))(2){o-C(6)H(4)(CH(2)SEt)(2)}] (8). However, replacing GaCl(3) with InCl(3) with o-C(6)H(4)(CH(2)SEt)(2) preferentially forms the 4:3 In:L complex [(InCl(3))(4){o-C(6)H(4)(CH(2)SEt)(2)}(3)] (9) containing discrete tetranuclear moieties in which the central In atom is octahedrally coordinated to six bridging Cl's, while the three In atoms on the edges have two bridging Cl's, two terminal Cl's, and two mutually trans S-donor atoms from different dithioether ligands. GaCl(3) also reacts with the cyclic bidentate [8]aneSe(2) to form a colorless, extremely air-sensitive adduct formulated as [(GaCl(3))(2)([8]aneSe(2))] (10), while InCl(3) gives [InCl(3)([8]aneSe(2))] (14). Very surprisingly, 10 reacts rapidly with O(2) gas to give initially the red [{[8]aneSe(2)}(2)][GaCl(4)](2) (11) and subsequently the yellow [{[8]aneSe(2)}Cl][GaCl(4)] (12). The crystal structure of the former confirms a dimeric [{[8]aneSe(2)}(2)](2+) dication, derived from coupling of two mono-oxidized {[8]aneE(2)}(+•) cation radicals to form an Se-Se bond linking the rings and weaker transannular 1,5-Se···Se interactions across both rings. The latter (yellow) product corresponds to discrete doubly oxidized {[8]aneSe(2)}(2+) cations (with a primary Se-Se bond across the 1,5-positions of the ring) with a Cl(-) bonded to one Se. Tetrahedral [GaCl(4)](-) anions provide charge balance in each case. These oxidation reactions are clearly promoted by the Ga(III) since [8]aneSe(2) itself does not oxidize in air. The new complexes have been characterized in the solid state by IR and Raman spectroscopy, microanalysis, and X-ray crystallography where possible. Where solubility permits, the solution characteristics have been probed by (1)H, (77)Se{(1)H}, and (71)Ga NMR spectroscopic studies.

Telluroether and Selenoether Complexes as Single Source Reagents for Low Pressure Chemical Vapor Deposition of Crystalline Ga2Te3 and Ga2Se3 Thin Films

“…20 All of the complexes containing mono-or simple acyclic dichalcogenoethers adopt distorted tetrahedral coordination environments, with a single chalcogen donor ligand, whereas using macrocyclic tetrathioethers or tetraselenoethers leads to higher chalcogen coordination at Ga, leading to five-or six-coordinate species. 24 While the thioether and selenoether complexes are stable under a dry N 2 -atmosphere, the telluroether complexes are more sensitive. No materials deposition studies on these types of reagents have been made prior to the present study.…”

Phosphine complexes of aluminium(iii) halides – preparation and structural and spectroscopic systematics

“…5 DFT calculations predict that the bond lengths involving neutral ligands for a fixed metal (Al, Ga or In) generally increase (for gas phase molecules) Cl < Br < I, reflecting decreasing Lewis acidity down the series. 5,[7][8][9] However, in some cases solid state effects ( packing effects, intermolecular interactions, hydrogen bonding or interaction with solvent molecules) can mask this trend. 9 In order to explore the issue of size between Al and Ga centres, we compared d(M-X) (X = Cl, Br or I) for the fourcoordinate [MX 4 ] − ions, with data taken from the Cambridge Structural Database.…”

“…The trend to higher coordination numbers found for aluminium(III) is thus an electronic effect, resulting from higher Lewis acidity towards phosphine ligands, as predicted by the DFT studies. 7,15…”

Thio-, seleno- and telluro-ether complexes of aluminium(iii) halides: synthesis, structures and properties

“…or dinuclear [X 3 Ga(μ-L-L)GaX 3 ] (L-L = RS-(CH 2 ) 2 SR, MeSe(CH 2 ) 2 SeMe, MeTe(CH 2 ) 3 TeMe etc.). [11][12][13][14] Higher coordination numbers are rare in the gallium systems, but found with the thia-macrocycle [14]aneS 4 , ‡ which binds exodentate via two sulfur centres, affording the chain polymer [GaCl 3 ([14]aneS 4 )] with a trigonal bipyramidal geometry. 15 15,16 We have recently reported that [GaCl 3 ( n Bu 2 E)] (E = Se or Te) or [GaCl 3 {μ-n BuE(CH 2 ) n E n Bu)GaCl 3 ] are effective single source precursors for low pressure chemical vapour deposition (LPCVD) of Ga 2 E 3 thin films, and that preferential deposition occurs onto TiN in photolithographically patterned SiO 2 /TiN substrates.…”