Germyl Cation Research Articles

Synthesis of Germacyclic Compounds by Cyclization and Annulation Reactions Utilizing In Situ Generated Germyl Cations

Germyl cations are one of the heavier group 14 element analogues of carbocations and have been extensively studied for their structures, spectroscopic features, and reactivities to various molecule...

Functionalized alkynyl-chlorogermanes: hydrometallation, Ge-Cl bond activation, Ge-H bond formation and chlorine-tert-butyl exchange via a transient germyl cation.

Treatment of alkynyl-arylchlorogermanes ArylnGe(Cl)(C[triple bond, length as m-dash]C-(t)Bu)3-n (n = 1, 2) with HM(t)Bu2 (M = Al, Ga) yielded mixed Al or Ga alkenyl-alkynylchlorogermanes via hydrometallation reactions. Intramolecular interactions between the Lewis-basic Cl atoms and the Lewis-acidic Al or Ga atoms afforded MCGeCl heterocycles. The endocyclic M-Cl distances were significantly lengthened compared to the starting compounds and indicated Ge-Cl bond activation. Dual hydrometallation succeeded only with HGa(t)Bu2. One Ga atom of the product was involved in a Ga-Cl bond, while the second one had an interaction to a C-H bond of a phenyl group. In two cases treatment of chlorogermanes with two equivalents of HAl(t)Bu2 resulted in hydroalumination of one alkynyl group and formation of unprecedented Ge-H functionalized germanes, Aryl-Ge(H)(C[triple bond, length as m-dash]C-(t)Bu)[C(Al(t)Bu2)[double bond, length as m-dash]C(H)-(t)Bu] (Aryl = mesityl, triisopropylphenyl). The Al atoms of these compounds interacted with the α-C atoms of the alkynyl groups. Ph(Cl)Ge(C[triple bond, length as m-dash]C-(t)Bu)[C(Al(t)Bu2}[double bond, length as m-dash]C(H)-(t)Bu] reacted in an unusual Cl/(t)Bu exchange to yield the tert-butylgermane Ph((t)Bu)Ge(C[triple bond, length as m-dash]C-(t)Bu)[C{Al((t)Bu)(Cl)}[double bond, length as m-dash]C(H)-(t)Bu]. Quantum chemical calculations suggested the formation of a germyl cation as a transient intermediate.

Cooperative Ge-N Bond activation in aluminium-functionalised aminogermanes and spontaneous imine elimination via an intermediate germyl cation.

Hydrometallation of iPr2 N-Ge(CMe3 )(C≡C-CMe3 )2 with H-M(CMe3 )2 (M=Al, Ga) affords alkenyl-alkynylgermanes in which the Lewis-acidic metal atoms are not coordinated by the amino N atoms but by the α-C atoms of the ethynyl groups. These interactions result in a lengthening of the Ge-C bonds by approximately 10 pm and a comparably strong deviation of the Ge-CC angle from linearity (154.3(1)°). This unusual behaviour may be caused by steric shielding of the N atoms. Coordination of the metal atoms by the amino groups is observed upon hydrometallation of Et2 N-Ge(C6 H5 )(C≡C-CMe3 )2 , bearing a smaller NR2 group. Strong M-N interactions lead to a lengthening of the Ge-N bonds by 10 to 15 pm and a strong deviation of the M atoms from the MC3 plane by 52 and 47 pm, for Al and Ga, respectively. Dual hydrometallation is achieved only with HAl(CMe3 )2 . In the product, there is a strong Al-N bond with converging Al-N and Ge-N distances (208 vs. 200 pm) and an interaction of the second Al atom to the phenyl group. Addition of chloride anions terminates the latter interaction while the activated Ge-N bond undergoes an unprecedented elimination of EtN=C(H)Me at room temperature, leading to a germane with a Ge-H bond. State-of-the-art DFT calculations reveal that the unique mechanism comprises the transfer of the amino group from Ge to Al to yield an intermediate germyl cation as a strong Lewis acid, which induces β-hydride elimination, with chloride binding being crucial for providing the thermodynamic driving force.

Germyl Cations with Ge–S Bonds: An Experimental and Theoretical Study on the Gaseous FnGe(SH)+3–n (n = 0–2)

The germyl cations F(2)Ge(SH)(+), FGe(SH)(2)(+) and Ge(SH)(3)(+) were obtained from ionized mixtures of GeF(4) and H(2)S. Ion trap mass spectrometry revealed the occurrence of three consecutive addition-HF elimination reactions between GeF(3)(+), F(2)Ge(SH)(+) and FGe(SH)(2)(+) and H(2)S. The structure and the mechanism of formation of the observed F(n)Ge(SH)(3-n)(+) (n = 0-2) were investigated by ab initio calculations performed at the MP2 and coupled cluster level of theory. It was also possible to note regular trends in the geometries and Lewis acidities of the F(n)Ge(SH)(3-n)(+) (n= 0-3).

Gaseous germyl cations: A theoretical investigation on the structure, properties, and mechanism of formation of [formula omitted] and [formula omitted] (n = 0–2)

The six germyl cations FnGe(OH)3-n+ and FnGe(NH2)3-n+ (n=0–2), recently observed in the gas phase from the cascade reactions between GeF3+ and H2O or NH3 (J. Mass Spectrom. 46 (2011) 465–477), were theoretically investigated by MP2 and CCSD(T) calculations. The bond distances and the electronic properties of these ions, and the stabilities of their complexes with H2O, NH3, and HF are regularly affected by the nature of the substituents. In particular, any Ge–X bond (X=F, OH, NH2) becomes progressively shorter by increasing the electronegativity of the two adjacent groups, and the most electronegative substituents produce also highest atomic charges at the Ge atom. In addition, replacing F with OH and NH2, the thermochemical stability of the cations substantially increases. This reflects in Lewis acidities of the F2Ge(X)+ and FGe(X)2+ (X=OH, NH2) which are invariably lower than GeF3+. The mechanisms of formation of the FnGe(OH)3-n+ and FnGe(NH2)3-n+ (n=0–2) were also investigated and found to be describable by the initial formation of encounter complexes between the reactant ions GeF3+, F2Ge(X)+ and FGe(X)2+ (X=OH, NH2) and H2O or NH3, which eventually dissociate into FnGe(OH)3-n+ and FnGe(NH2)3-n+ (n=0–2) and HF passing through two consecutive isomerizations.

(OtBu)2C6H3]3Ge+a free germyl cation with aryl ligands

The reaction of Ar(3)GeBr (Ar = 2,6-(OtBu)(2)C(6)H(3)), which is the side product of the synthesis of the metalloid germanium cluster compound Ge(8)Ar(6), with the silver salt of the weakly coordinating anion (WCA) [Al(OR(f))(4)](-) (R(f) = C(CF(3))(3)) gives the free germyl cation Ar(3)Ge(+). Quantum chemical calculations open an insight into the bonding situation of this first free cation exhibiting aryl ligands and a first reaction leading to Ar(3)GeOH is presented.

1,4,5-trigermabicyclo[2.1.0]pent-2-en-5-ylium: the isolable bishomocyclopropenylium ion containing a heavier group 14 element.

The isolable bishomoaromatic cation containing a heavier Group 14 element, (2,3,5-deloc)-2-phenyl-1,4,5-tris(tri-tert-butylsilyl)-1,4,5-trigermabicyclo[2.1.0]pent-2-en-5-ylium TPFPB- (2+.TPFPB-; TPFPB- = tetrakis(pentafluorophenyl)borate) was synthesized by the reaction of 5-bromo-2-phenyl-1,4,5-tris(tri-tert-butylsilyl)-1,4,5-trigermabicyclo[2.1.0]pent-2-ene (1) with [Et3Si(benzene)]+.TPFPB- in benzene at room temperature. The characteristic bishomoaromatic structure was unambiguously determined by X-ray crystallographic analysis. NMR measurements on 2+.TPFPB- confirmed the nonclassical germyl cation structure in solution and showed strong shielding of homoconjugative carbon atoms. The bishomoaromaticity in 2+ was also investigated by theoretical calculations.

Ligand exchange ion–molecule reactions of simple silyl and germyl cations

The gas-phase reaction of Me 3Si + with Si(OMe) 4, studied under FT-ICR conditions, reveals that aside from the expected silyl ion– n-donor base association an exchange mechanism exists that gives rise to Me 2SiOMe +. Further reaction of this ion was observed to result in a second exchange of a methyl group by a methoxy group in the silyl ion. The similar reaction between Me 3Si + and Ge(OMe) 4 yields not only the silyl ions with progressive exchange of methyl by methoxy but the different germyl ions, Me n Ge(OMe) 3− n + ( n=0–3). Ab initio calculations for the simple model system MeSiH 2 ++MeOGeH 3 reveal that these reactions proceed by initial formation of a very strong Lewis acid–base complex where migration of the germyl or silyl group can result in a moiety held together by an alkyl bridge. Methide abstraction in this intermediate can then give rise to silyl and germyl cations. The present results suggest that other Si and Ge systems may display this very same kind of rich chemistry.

Reaction of Bis[bis(trimethylsilyl)methyl]germylene with Tris(4-tert-butylphenyl)methylium Ion: Formation of a Unique Germyl Cation Weakly σ-Coordinated to Aromatic Group

Abstract The reaction of bis[bis(trimethylsilyl)methyl]germylene with tris(4-tert-butylphenyl)methylium TPFPB− in toluene produced an unexpected germyl cation, {[(Me3Si)2CH]Me2Si}{[(4-tert-BuC6H4)3C]Me2Si}-HCMe2Ge+, which was formed through several consecutive rearrangements of the methyl, bis(trimethylsilyl)methyl, and triarylmethyl groups.

The Cation Cluster of Heavier Group 14 Elements: A Free Germyl Cation with Trishomoaromaticity

The heavier group 14 element cation cluster compound, [(tBu3Si)6Ge10I]+.TTFPB- (3+. TTFPB-; TTFPB- = tetrakis(2,3,5,6-tetrafluorophenyl)borate), was unexpectedly obtained by thermolysis of in situ prepared iodocyclotrigermene, (tBu3Si)3Ge3I, in toluene in the presence of KI and K+.TTFPB-. The molecular structure of 3+.TTFPB- has been unambiguously determined by X-ray crystallography, showing that 3+ is a free germyl cation. The three "naked" cationic germanium atoms in the framework constitute a three-center two-electron (3c-2e) bond with a trishomocyclotrigermenylium character, which is well-supported by a theoretical calculation on the model compound Ge10H7+.

Synthesis and Structure of Cyclotrigermenium Salts of Tetrakis{3,5-bis(trifluoromethyl)phenyl}borate, Tetrakis(pentafluorophenyl)borate and Tetrakis{4-[tert-butyl(dimethyl)silyl]-2,3,5,6-tetrafluorophenyl}borate: A Stable Free Germyl Cation in the Condensed Phase

Synthesis and Structure of Cyclotrigermenium Salts of Tetrakis{3,5-bis(trifluoromethyl)phenyl}borate, Tetrakis(pentafluorophenyl)borate and Tetrakis{4-[tert-butyl(dimethyl)silyl]-2,3,5,6-tetrafluorophenyl}borate: A Stable Free Germyl Cation in the Condensed Phase

Synthesis and Structure of Cyclotrigermenium Salts of Tetrakis{3,5‐bis(trifluoromethyl)phenyl}borate, Tetrakis(pentafluorophenyl)borate and Tetrakis{4‐[tert‐butyl(dimethyl)silyl]‐2,3,5,6‐tetrafluorophenyl}borate: A Stable Free Germyl Cation in the Condensed Phase

The reaction of tetrakis(tri-tert-butylsilyl)cyclotrigermene (1a) with Ph3C+[3,5-(CF3)2C6H3]4B− (TFPB−), Ph3C+(C6F5)4B− (TPFPB−), and Ph3C+[4-(tBuMe2Si)C6F4]4B− (TSFPB−) in benzene produced the stable free tris(tri-tert-butylsilyl)cyclotrigermenium ion (2a+) with the corresponding tetraarylborate as the counterion. The crystal structures of 2a+TFPB− and 2a+TSFPB− reveal a free germyl cation with a two π-electron system. The three-membered ring of germanium atoms constitutes an almost equilateral triangle. The cyclotrigermenium tetraarylborates, 2a+TFPB−, 2a+TPFPB−, and 2a+TSFPB−, are stable in solution. The spectroscopic data show that 2a+ is a free germyl cation, does not coordinate to either the solvent molecules (dichloromethane, chloroform, toluene, or diethyl ether) or the counter anions (TFPB−, TPFPB−, or TSFPB−). The tris(tri-tert-butylgermyl)cyclotrigermenium ion (2b+) was also characterized.

Novel Heteroleptic Germanium(II) Compounds from [2,4-Di-tert-butyl-6-((dimethylamino)methyl)phenyl]germanium Chloride: Synthesis, Structure, and Derivatization

The synthesis of novel heteroleptic germanium(II) compounds starting from [2,4-di-tert-butyl-6-((dimethylamino)methyl)phenyl]germanium chloride, MamxGeCl (1), is reported. 1 reacts with potassium alkoxides to give the alkoxy-substituted compounds MamxGeO-t-Bu (2), MamxGeO-i-Pr (3), MamxGeOEt (4), and MamxGeOMe (5). The ethynyl-substituted species MamxGe(C⋮CPh) (6) and MamxGe(C⋮CH) (7) are obtained by the reaction of 1 with LiC⋮CPh and NaC⋮CH, respectively. The alkyl-substituted germanium(II) species MamxGeR (R = t-Bu (8), n-Bu (9), Me (10)) are formed by the reaction of 1 with the corresponding alkyllithium compounds. Derivatization of 8−10 with MeI leads to the formation of compounds containing the germyl cations [MamxGe(t-Bu)(Me)]+ (11a), [MamxGe(n-Bu)(Me)]+ (12a), and [MamxGe(Me)2]+ (13a), respectively. All new species have been characterized by NMR, MS, and microanalytical data. X-ray crystal structure determinations are presented for 3, 4, 6, 7, and 11.

Cyclotrigermenium Ion by Oxidation of Cyclotrigermene with Trityl Tetrakis {3,5-Bis(Trifluoromethyl)Phenyl}Borate and Trityl Tetrakis(Pentafluoro-Phenyl)Borate. A Stable Free Germyl Cation in the Condensed Phase

The reaction of tetrakis(tri-t-butylsilyl) cyclotrigermene with Ph3C+z [3,5-(CF3)2C6H3]4B− (TFPB) and Ph3C+z(C6F5)4B− (TPFPB) in benzene produced the stable free tris (tri-t-butylsilyl)cyclotrigermenium ion (2a) with the corresponding tetraarylborate as a counter anion. The crystal structure of 2azTFPB reveals a free germyl cation with 2π-electron system. The three-membered germanium atoms constitute almost an equilateral triangle, similar to that of 2azTPB (TPB = Ph4B−). In contrast to 2azTPB, both 2azTFPB and 2azTPFPB are thermally stable in solution.

Cyclotrigermenium Ion by Oxidation of Cyclotrigermene with Trityl Tetrakis {3,5-Bis(Trifluoromethyl)Phenyl}Borate and Trityl Tetrakis(Pentafluoro-Phenyl)Borate. A Stable Free Germyl Cation in the Condensed Phase

The reaction of tetrakis(tri-t-butylsilyl) cyclotrigermene with Ph3C+z [3,5-(CF3)2C6H3]4B− (TFPB) and Ph3C+z(C6F5)4B− (TPFPB) in benzene produced the stable free tris (tri-t-butylsilyl)cyclotrigermenium ion (2a) with the corresponding tetraarylborate as a counter anion. The crystal structure of 2azTFPB reveals a free germyl cation with 2π-electron system. The three-membered germanium atoms constitute almost an equilateral triangle, similar to that of 2azTPB (TPB = Ph4B−). In contrast to 2azTPB, both 2azTFPB and 2azTPFPB are thermally stable in solution.

Synthesis and Structure of Cyclotrigermenium Salt of the Tetrakis{3,5-bis(trifluoromethyl)phenyl}borate Anion. A Stable Free Germyl Cation in the Condensed Phase

Abstract The reaction of tetrakis(tri-t-butylsilyl)cyclotrigermene with Ph3C+·[3,5-(CF3)2C6H3]B− (TFPB) and Ph3C+·(C6F5)4B− (TPFPB) in benzene produced the stable free tris(tri-t-butylsilyl)cyclotrigermenium ion (2a) with the corresponding tetraarylborate as a counter anion. The crystal structure of 2a·TFPB reveals a free germyl cation with a 2π-electron system.

Germylenes and Germyl Cations with the 2,4-Di-tert-butyl-6-(N,N-dimethylaminomethyl)phenyl Ligand

The 2,4-di-tert-butyl-6-(N,N-dimethylaminomethyl)phenyl (Mamx) ligand allows the synthesis of the germylenes MamxGeCl (I), Mamx(2)Ge (2), Mamx(Tip)Ge (3; Tip = 2,4,6-iPr(3)C(6)H(2)), MamxGeN(3) (4), MamxGeN(SiMe3)(2) (5), and MamxGe[Fe(CO)(2)Cp*] (6), which are all stabilized by coordination of the amino side chain. Reactions of 2 and 3 with Mel yield the ionic compounds Mamx(Tip)(Me)Ge+I-(7) and Mamx(2)(Me)Ge+I- (8), respectively; the X-ray crystal structure of 7 shows a trigonal-planar coordination at the Ge center and a nearly perpendicular Ge-N bond.

ChemInform Abstract: Free or Not, That is the Question: Silyl and Germyl Cations in Condensed Phases

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Free or Not, That Is the Question: Silyl and Germyl Cations in Condensed Phases

“The search for an isolable silyl cation must continue” was the title of a paper in this journal a few years ago. Recently, J. Lambert et al. reported the latest results of this continued search: the trimesitylsilyl cation is a practically free silyl cation in aromatic solvents. Kinetic and thermodynamic stabilization have now also allowed the isolation of the noncoordinated germirene cation 1 by A. Sekiguchi et al.

Cyclotrigermenium Ion, a Free Germyl Cation with 2π-Electron System

The reaction of tetrakis(tri-t-butylsilyl)cyclotrigermene with trityl tetraphenylborate in benzene produced tris(tri-t-butylsilyl)cyclotrigermenium tetraphenylborate [(t-Bu3SiGe)3 +BPh4 -], which can be isolated as yellow solids stable in the absence of air. The crystal structure of the cyclotrigermenium ion reveals a free germyl cation with 2π-electron system.