On the Gallanyls R*3Ga2· and R*4Ga3· As Well As Gallanides R*3Ga2− and R*4Ga3− (R* = SitBu3) − Syntheses, Characterization, Structures

Abstract

The reduction of black‐blue tris(supersilyl)digallanyl [R*2Ga−GaR*]· (R* = SitBu3 = supersilyl) in organic solvents with Na, NaC10H8, or NaR* leads to deep‐red sodium tris(supersilyl)digallanide−THF(1/3) NaGa2R*3×3THF = [R*2Ga−GaR*Na(THF)3], which transforms in the presence of 18‐crown‐6 into deep‐blue sodium tetrakis(supersilyl)trigallanide−18‐crown‐6(1/1)−THF(1/2) [Na(18‐C‐6)(THF)2]+[R*2Ga−GaR*−GaR*]−.The oxidation of the latter anion with R*Br or TCNE as well as the reaction of the digallanyl R*3Ga2· with R*Br leads to deep‐green tetra(supersilyl)cyclotrigallanyl [···R*Ga−GaR*2−GaR*···]·. The latter radical thermolizes at 100 °C to dark‐violet tetrakis(supersilyl)‐tetrahedro‐tetragallane R*4Ga4 besides the digallanyl R*3Ga2·. This is also prepared from NaR* and GaCl3 or R*2GaCl, as well as by oxidation of R*3Ga2−, and itself thermolizes with formation of the tetrahedrane R*4Ga4. According to X‐ray structure analyses of the mentioned compounds, the Ga−Ga bond of the digallanide NaGa2R*3×3THF (NMR spectroscopically observed) is comparably short (2.380 Å), approaching a bond order of 2. In fact, it is distinctly shorter than the Ga−Ga bond (2.420 Å) in the digallanyl R*3Ga2· (EPR spectroscopically observed). The Ga atoms of the trigallanyl R*4Ga3· (EPR spectroscopically observed) are located at the corners of a triangle with two shorter R*2Ga−GaR* sides (2.527 Å) and a comparably longer R*Ga−GaR* basis (2.879 Å). The mean value of the two Ga−Ga bonds in the trigallanide R*4Ga3− (NMR spectroscopically observed) is as long (2.53 Å) as the short Ga−Ga bonds in R*4Ga3·. The anion shows an intramolecular CH3···Ga contact (C−Ga 2.10 Å) between one peripheral methyl group of the R*2Ga entity and the anionic Ga atom in [R*2Ga−GaR*−GaR*]−.

Ditrielanes (R3Si)2E−E(SiR3)2 and Heterocubanes (R3Si)4E4Y4 (R3Si =tBu3Si,tBu2PhSi; E = Al, Ga, In, Tl; Y = O, Se)

“…Isolable intermediates are R*EHal 2 [1,2] and R* 2 EHal. [1,2] As already discussed elsewhere, [5] NaR* reacts with R* 2 EHal under NaHal elimination to radicals R* • and R* 2 E • . For steric reasons only the dimerization of the radicals under formation of R* 2 and (R* 2 E) 2 is possible and no recombination of both radicals to form R* 3 E occurs (the cone angle for R* amounts to 130°; [15] even R* 2 Tl ϩ and NaR* give R* 4 Tl 2 and not R* 3 Tl [7] ).…”

Ditrielanes (R3Si)2E−E(SiR3)2 and Heterocubanes (R3Si)4E4Y4 (R3Si =tBu3Si,tBu2PhSi; E = Al, Ga, In, Tl; Y = O, Se)

“…Isolable intermediates are R*EHal 2 [1,2] and R* 2 EHal. [1,2] As already discussed elsewhere, [5] NaR* reacts with R* 2 EHal under NaHal elimination to radicals R* • and R* 2 E • . For steric reasons only the dimerization of the radicals under formation of R* 2 and (R* 2 E) 2 is possible and no recombination of both radicals to form R* 3 E occurs (the cone angle for R* amounts to 130°; [15] even R* 2 Tl ϩ and NaR* give R* 4 Tl 2 and not R* 3 Tl [7] ).…”

π-Bonding and the Lone Pair Effect in Multiple Bonds Involving Heavier Main Group Elements: Developments in the New Millennium

“…These papers have described spectroscopic and theoretical studies of a matrix isolated OCBBCO at low temperature and of a B 2 (BO) 2 2− cluster in the vapor phase. − The calculations afforded BB distances near 1.45 Å in both molecules, which is in good agreement with the 1.46 Å predicted by the sum of the triple bond radii . The currently known stable species with potential triple bonding involving group 13 elements are listed in Table . ,,,− ,,− …”

Metalloid Aluminum and Gallium Clusters: Element Modifications on the Molecular Scale?

“…Therefore this Ga 2 unit (or a [Ga 2 Na 2 ] 2+ cluster) lies on the borderline between the Zintl anions on the one side104 and the metalloid gallium clusters with their intermediate oxidation states between +1 and 0 on the other. A similar analysis leads from the [Ga 3 R 3 Na 2 ] species ( 12 ; R=2,6‐C 6 H 3 Mes 2 ; Mes=2,4,6‐C 6 H 2 Me 3 )62 to the [Ga 3 Na 2 ] 3+ units63 or from the [Ga 4 R 2 K 2 ] compound ( 13 ; Figure 16 c R=2,6‐C 6 H 3 Trip 2 ) 64 to the [Ga 4 K 2 ] 2+ and [Ga 4 0 ] clusters 105. Since the GaNa and GaK bond lengths in all the clusters of this type lie in the ranges anticipated from the sum of the metal radii, an assessment with the help of additional quantum‐chemical calculations65 should lead to a deeper understanding of the bonding in these Ga clusters that goes beyond the merely descriptive use of the term GaGa multiple bonds 60…”

Ditrielanes (R3Si)2E−E(SiR3)2 and Heterocubanes (R3Si)4E4Y4 (R3Si =tBu3Si,tBu2PhSi; E = Al, Ga, In, Tl; Y = O, Se)

“…Isolable intermediates are R*EHal 2 [1,2] and R* 2 EHal. [1,2] As already discussed elsewhere, [5] NaR* reacts with R* 2 EHal under NaHal elimination to radicals R* • and R* 2 E • . For steric reasons only the dimerization of the radicals under formation of R* 2 and (R* 2 E) 2 is possible and no recombination of both radicals to form R* 3 E occurs (the cone angle for R* amounts to 130°; [15] even R* 2 Tl ϩ and NaR* give R* 4 Tl 2 and not R* 3 Tl [7] ).…”

π-Bonding and the Lone Pair Effect in Multiple Bonds Involving Heavier Main Group Elements: Developments in the New Millennium

“…These papers have described spectroscopic and theoretical studies of a matrix isolated OCBBCO at low temperature and of a B 2 (BO) 2 2− cluster in the vapor phase. − The calculations afforded BB distances near 1.45 Å in both molecules, which is in good agreement with the 1.46 Å predicted by the sum of the triple bond radii . The currently known stable species with potential triple bonding involving group 13 elements are listed in Table . ,,,− ,,− …”

Metalloid Aluminum and Gallium Clusters: Element Modifications on the Molecular Scale?

“…Therefore this Ga 2 unit (or a [Ga 2 Na 2 ] 2+ cluster) lies on the borderline between the Zintl anions on the one side104 and the metalloid gallium clusters with their intermediate oxidation states between +1 and 0 on the other. A similar analysis leads from the [Ga 3 R 3 Na 2 ] species ( 12 ; R=2,6‐C 6 H 3 Mes 2 ; Mes=2,4,6‐C 6 H 2 Me 3 )62 to the [Ga 3 Na 2 ] 3+ units63 or from the [Ga 4 R 2 K 2 ] compound ( 13 ; Figure 16 c R=2,6‐C 6 H 3 Trip 2 ) 64 to the [Ga 4 K 2 ] 2+ and [Ga 4 0 ] clusters 105. Since the GaNa and GaK bond lengths in all the clusters of this type lie in the ranges anticipated from the sum of the metal radii, an assessment with the help of additional quantum‐chemical calculations65 should lead to a deeper understanding of the bonding in these Ga clusters that goes beyond the merely descriptive use of the term GaGa multiple bonds 60…”

Ditrielanes (R3Si)2E−E(SiR3)2 and Heterocubanes (R3Si)4E4Y4 (R3Si =tBu3Si,tBu2PhSi; E = Al, Ga, In, Tl; Y = O, Se)

“…Isolable intermediates are R*EHal 2 [1,2] and R* 2 EHal. [1,2] As already discussed elsewhere, [5] NaR* reacts with R* 2 EHal under NaHal elimination to radicals R* • and R* 2 E • . For steric reasons only the dimerization of the radicals under formation of R* 2 and (R* 2 E) 2 is possible and no recombination of both radicals to form R* 3 E occurs (the cone angle for R* amounts to 130°; [15] even R* 2 Tl ϩ and NaR* give R* 4 Tl 2 and not R* 3 Tl [7] ).…”

π-Bonding and the Lone Pair Effect in Multiple Bonds Involving Heavier Main Group Elements: Developments in the New Millennium

“…These papers have described spectroscopic and theoretical studies of a matrix isolated OCBBCO at low temperature and of a B 2 (BO) 2 2− cluster in the vapor phase. − The calculations afforded BB distances near 1.45 Å in both molecules, which is in good agreement with the 1.46 Å predicted by the sum of the triple bond radii . The currently known stable species with potential triple bonding involving group 13 elements are listed in Table . ,,,− ,,− …”

Metalloid Aluminum and Gallium Clusters: Element Modifications on the Molecular Scale?

“…Therefore this Ga 2 unit (or a [Ga 2 Na 2 ] 2+ cluster) lies on the borderline between the Zintl anions on the one side104 and the metalloid gallium clusters with their intermediate oxidation states between +1 and 0 on the other. A similar analysis leads from the [Ga 3 R 3 Na 2 ] species ( 12 ; R=2,6‐C 6 H 3 Mes 2 ; Mes=2,4,6‐C 6 H 2 Me 3 )62 to the [Ga 3 Na 2 ] 3+ units63 or from the [Ga 4 R 2 K 2 ] compound ( 13 ; Figure 16 c R=2,6‐C 6 H 3 Trip 2 ) 64 to the [Ga 4 K 2 ] 2+ and [Ga 4 0 ] clusters 105. Since the GaNa and GaK bond lengths in all the clusters of this type lie in the ranges anticipated from the sum of the metal radii, an assessment with the help of additional quantum‐chemical calculations65 should lead to a deeper understanding of the bonding in these Ga clusters that goes beyond the merely descriptive use of the term GaGa multiple bonds 60…”