Solid Phase Synthesis of a Functionalized Bis-Peptide Using …
Published 5/15/2012
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In JoVE (1)
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Articles by Miriam M. Gillett-Kunnath in JoVE
Synthesis of Nine-atom Deltahedral Zintl Ions of Germanium and their Functionalization with Organic Groups
Department of Chemistry and Biochemistry, University of Notre Dame
We present the high-temperature synthesis of intermetallic precursors K4Ge9, their dissolution in ethylenediamine to form Ge94- deltahedral Zintl ions, and the reaction of the clusters with alkynes to form organo-Zintl ions. The latter are characterized by electrospray mass spectrometry in solutions and by single-crystal X-ray diffraction in the solid state.
Other articles by Miriam M. Gillett-Kunnath on PubMed
BiPh3--a Convenient Synthon for Heavy Alkaline-earth Metal Amides
Environmentally friendly, commercially available BiPh3 reacts with heavy alkaline-earth metals (Ae) and bulky trimethylsilylamines to give the corresponding amides [Ae{N(SiMe3)(R)}2(thf)n] (R=SiMe3, 2,4,6-Me3C6H2, 2,6-iPr2C6H3) in good yields, providing proof of concept for a general synthetic method.
Heteroatomic Deltahedral Zintl Ions of Group 14 and Their Alkenylation
Reported is the synthesis of Ge(9-x)Sn(x) heteroatomic deltahedral Zintl ions and their alkenylation by reactions with alkynes. The nine-atom clusters are made either by extraction from mixed Ge/Sn precursors with nominal composition K(4)Ge(9-x)Sn(x) or by dissolution of mixtures of the corresponding binary precursors K(4)Ge(9) and K(4)Sn(9) in solvents with high dielectric constants such as DMF, DMSO, and acetonitrile. Reactions of the heteroatomic clusters with alkynes such as Me(3)SiC[triple bond]CSiMe(3), HC[triple bond]CCpr (Cpr = cyclopropyl), and HC[triple bond]CPh in ethylenediamine resulted in the following structurally characterized compounds with alkenylated heteroatomic clusters: [K-(2,2,2-crypt)](3)[GeSn(8)-CH=CH(2)].en.tol (1), triclinic, P1, a = 13.9220(3) A, b = 14.9788(3) A, and c = 21.5892(5) A, alpha = 94.2580(10) degrees , beta = 98.5210(10) degrees , and gamma = 98.4890(10) degrees , V = 4382.31(16) A(3), Z = 2; [K-(2,2,2-crypt)](4)[Ge(2)Sn(7)(CH=CH(2))(2)](2).en (2), monoclinic, P2(1)/c, a = 48.1883(15) A, b = 12.1551(4) A, and c = 21.4824(7) A, beta = 90.052(2) degrees , V = 12583.0(7) A(3), Z = 4; [K-(2,2,2-crypt)](3)[GeSn(8)-CH=CHCpr].en (3), monoclinic, P2(1)/c, a = 17.9132(9) A, b = 22.7967(11) A, and c = 21.6922(12) A, beta = 98.409(2) degrees , V = 8763.0(8) A(3), Z = 4; [K-(2,2,2-crypt)](3)[Ge(2)Sn(7)-CH=CHPh].2en (4), monoclinic, P2(1)/n, a = 13.2583(5) A, b = 47.0565(17) A, and c = 15.9978(6) A, beta = 111.536(2) degrees , V = 9284.1(6) A(3), Z = 4. The potassium countercations of the divinyl-substituted cluster in 2 were exchanged for tetrapropylammonium cations, and the resulting compound was also crystallized and structurally characterized: [Pr(4)N](4)[Ge(2)Sn(7)(CH=CH(2))(2)](2) (5), triclinic, P1, a = 11.6757(8) A, b = 18.8150(16) A, and c = 21.0608(17) A, alpha = 112.327(3) degrees , beta = 91.550(3) degrees , and gamma = 91.892(3) degrees , V = 4273.5(6) A(3), Z = 2. All clusters were also characterized in solution by electrospray mass spectrometry.
Addition of a Thallium Vertex to Empty and Centered Nine-atom Deltahedral Zintl Ions of Germanium and Tin
Nickel atoms were inserted into nine-atom deltahedral Zintl ions of E(9)(4-) (E = Ge, Sn) via reactions with Ni(cod)(2) (cod = cyclooctadiene), and [Ni@Sn(9)](3-) was structurally characterized. Both the empty and the Ni-centered clusters react with TlCp (Cp = cyclopentadienyl anion) and add a thallium vertex to form the deltahedral ten-atom closo-species [E(9)Tl](3-) and [Ni@E(9)Tl](3-), respectively. The structures of [Ge(9)Tl](3-) and [Ni@Sn(9)Tl](3-) showed that, as expected, the geometry of the ten-atom clusters is that of a bicapped square antiprism where the Tl-atom occupies one of the two capping vertices. This illustrates that centering a nine-atom cluster with a nickel atom does not change its reactivity toward TlCp. All compounds were characterized by electrospray mass spectrometry.
"n-Doping" of Deltahedral Zintl Ions
We report a simple and efficient method for replacing germanium atoms in deltahedral Ge(9)(4-) clusters with Sb or Bi. While reactions of Ge(9)(4-) with EPh(3) (E = Sb, Bi) at room temperature are known to produce mono- and disubstituted clusters [Ph(2)E-Ge(9)-Ge(9)-EPh(2)](4-) and [Ph(2)E-Ge(9)-EPh(2)](2-), respectively, at elevated temperatures or with sonication they result in exchange of Ge cluster atoms with Sb or Bi. Structurally characterized from such reactions are the novel "n-doped" deltahedral Zintl ions [(EGe(8))-(Ge(8)E)](4-), (Sb(2)Ge(7))(2-), and [(SbGe(8))-SbPh(2)](2-).
Metal-centered Deltahedral Zintl Ions: Synthesis of [Ni@Sn9]4- by Direct Extraction from Intermetallic Precursors and of the Vertex-fused Dimer [{Ni@Sn8(μ-Ge)(1/2)}2]4-
Ni-centered deltahedral Sn(9) clusters with a charge of 4-, i.e., [Ni@Sn(9)](4-), were extracted in ethylenediamine in high yield directly from intermetallic precursors with the nominal composition "K(4)Sn(9)Ni(3)". The new endohedral clusters were crystallized and structurally characterized in K[K(18-crown-6)](3)[Ni@Sn(9)]·3benzene (1a, triclinic, P1̅, a = 10.2754(5) Å, b = 19.5442(9) Å, and c = 20.5576(13) Å, α = 73.927(3)°, β = 79.838(4)°, and γ = 84.389(3)°, V = 3899.6(4) Å(3), Z = 2) and K[K(2,2,2-crypt)](3)[Ni@Sn(9)] (1b, triclinic, P1, a = 15.8028(8) Å, b = 16.21350(9) Å, and c = 20.1760(12) Å, α = 98.71040(10)°, β = 104.4690(10)°, and γ = 118.3890(10)°, V = 4181.5(4) Å(3), Z = 2). The alternative method of a post-synthetic insertion of a Ni atom in empty Sn(9) clusters by a reaction with Ni(cod)(2) predominantly produces the more-oxidized clusters with a charge of 3-, i.e., the recently reported [Ni@Sn(9)](3-). Nonetheless, using substoichiometric amounts of 18-crown-6 as a cation sequestering agent, we also have been able to isolate the 4- clusters as a minor phase from such reactions. They were structurally characterized in K[K(en)][K(18-crown-6)](2)[Ni@Sn(9)]·0.5en (2, monoclinic, P2(1)/n, a = 10.4153(5) Å, b = 25.6788(11) Å, and c = 20.6630(9) Å, β = 102.530(2)°, V = 5394.7(4) Å(3), Z = 2). The ability of the Ni-centered clusters to exist with both 3- and 4- charges parallels the same ability of the empty clusters and is very promising for similarly rich chemistry involving electron transfer and flexible "oxidation states". We also report the synthesis and characterization of the endohedral heteroatomic dimer [{Ni@Sn(8)(μ-Ge)(1/2)}(2)](4-) composed of two [Ni@(Sn(8)Ge)]-clusters fused at the Ge-vertex. The dimer was synthesized by reacting an ethylenediamine solution of a ternary precursor with the nominal composition "K(4)Ge(4.5)Sn(4.5)", which is known to produce heteroatomic Ge(9-x)Sn(x) clusters, with Ni(cod)(2). It is isostructural with the reported [{Ni@Sn(8)(μ-Sn)(1/2)}(2)](4-) and is structurally characterized in [K-(2,2,2-crypt)](4)[{Ni@Sn(8)(μ-Ge)(1/2)}(2)]·2en (3, monoclinic, C2/c, a = 30.636(2) Å, b = 16.5548(12) Å, and c = 28.872(2) Å, β = 121.2140(10)°, V = 12523.5(15) Å(3), Z = 4).