Eclipsed- and Staggered-[Ge18Pd3{EiPr3}6]2- (E = Si, Sn): Positional Isomerism in Deltahedral Zintl Clusters.

We report the synthesis and characterization of the cluster anions [Ge18Pd3{SiiPr3}6]2- (1) with a core of face-fused twinned icosahedra, Ge18Pd3, and two sets of three iPr3Si-substituents positioned in "eclipsed" geometry. The new anion is a positional isomer of the recently reported "staggered" stannyl-ligated counterpart [Ge18Pd3{SniPr3}6]2- (2), showing the possibility to find such positional isomerism in Zintl clusters. Both anions are characterized by single-crystal X-ray diffraction, 1H and 13C NMR, and negative-ion ESI-MS. Using relativistic DFT calculations, we elucidate and discuss the reasons for the different positioning of the ligands in the stannyl- and silyl-functionalized species.

A Stannyl-Decorated Zintl Ion [Ge18Pd3(Sn(i)Pr3)6](2-): Twinned Icosahedron with a Common Pd3-Face or 18-Vertex Hypho-Deltahedron with a Pd3-Triangle Inside.

We report the synthesis and characterization of the title anion which has a germanium/palladium cluster core of [Ge18Pd3] and six tri-isopropyl tin substituents. Its two Ge9-halves are the first examples of germanium deltahedra with three nonsilyl substituents, tri-isopropyl tin in this case. The new cluster is made by a reaction of an acetonitrile suspension of K4Ge9 with (i)Pr3SnCl that generates primarily tristannylated 9-atom clusters [Ge9{Sn(i)Pr3}3](-), followed by addition of Pd(PPh3)4 to the reaction mixture. It was structurally characterized by single-crystal X-ray diffraction in [K(222crypt)]2[Ge18Pd3{Sn(i)Pr3}6]·(i)Pr2O and was also confirmed in solution by ESI-MS and NMR. The new anion can be viewed both as a dimer of face-fused icosahedra (twinned icosahedron) with a common Pd3-face, i.e., [((i)Pr3Sn)3Ge9Pd3Ge9(Sn(i)Pr3)3](2-) that resembles but is not isoelectronic with the known borane version B21H18(-) or as a large hypho-deltahedron of 18 Ge-atoms with a triangle of Pd3 inside, i.e., [Pd3@Ge18(Sn(i)Pr3)6](2-). DFT calculations show a very large HOMO-LUMO gap of 2.42 eV.

[(Me3 Si)Si]3 EtGe9 Pd(PPh3 ), a Pentafunctionalized Deltahedral Zintl Cluster: Synthesis, Structure, and Solution Dynamics.

The title compound, which has a ten-atom deltahedral cluster core of Ge9 Pd, was synthesized through insertion of Pd(PPh3 ) into the tetrasubstituted nona-germanium cluster [(Me3 Si)Si]3 EtGe9 through a reaction of the latter with Pd(PPh3 )4 . This first reaction of neutral tetrasubstituted nine-atom clusters shows that they retain reactivity despite their neutral charge. The Ge9 Pd core is the first that incorporates a 5-connected transition metal other than from Group VI, a noble metal in this case. Single-crystal X-ray diffraction shows that the ten-atom core is a closo-cluster with the expected shape of a bicapped square antiprism. (1) H and (13) C NMR spectroscopy show that, in contrast to the parent tetra-substituted [(Me3 Si)Si]3 EtGe9 , the new compound does not exhibit dynamics. Relativistic DFT calculations are used to explain the differences.

Cluster Fusion: Face-Fused Nine-Atom Deltahedral Clusters in [Sn14 Ni(CO)](4.).

The title anion was synthesized by heating dimethylformamide (DMF) solution of the known Ni-centered and Ni(CO)-capped tin clusters [Ni@Sn9 Ni(CO)](3-) . The new anion represents the first example of face-fused nine-atom molecular clusters. The two clusters are identical elongated tricapped trigonal prisms of nido-[Sn8 Ni(CO)](6-) with nickel at one of the capping positions. They are fused along a triangular face adjacent to a trigonal prismatic base and made of two Sn and one Ni atoms. The new anion is structurally characterized by single-crystal X-ray diffraction in the compound (K[222-crypt])4 [Sn14 Ni(CO)]⋅DMF. Its presence in solution is corroborated by electrospray mass spectrometry.

[Bi12Ni7(CO)4](4-): Aggregation of Intermetalloid Clusters by Their Thermal Deligation and Oxidation.

Reported are the synthesis and structure of the anionic intermetalloid cluster [Bi12Ni7(CO)4](4-). It was synthesized from the known smaller clusters Bi3Ni4(CO)6(3-), Bi3Ni6(CO)9(3-), and Ni@Bi6Ni6(CO)8(4-) by their aggregation as a result of thermal deligation and oxidation. The new cluster is structurally characterized by single-crystal X-ray diffraction in the compound (K[crypt])4[Bi12Ni7(CO)4] (1), and its presence in solution is confirmed by electrospray mass spectrometry. It can be viewed as composed of a Ni-centered icosahedral core of Bi6Ni6(CO)4 where two diametrically opposed Ni atoms are capped by Bi3 triangles. However, its electron count is rationalized based on a structure made of fused tetrahedra.

Coordination of Tri-Substituted Nona-Germanium Clusters to Cu(I) and Pd(0).

The recently developed approach for the rational functionalization of deltahedral nona-germanium clusters Ge9(4-) with three substituents to form Ge9R3(-) (R = Si(SiMe3)3) in large amounts has made the latter a convenient starting material for further reactivity studies. Reported here are the synthesis, structures, and solution studies of two compounds where Ge9R3(-) are used as ligands to transition metals, [(Ge9R3)Cu(I)(Ge9R3)Cu(I)PPh3] (1) and [(Ge9R3)Pd(0)(Ge9R3)](2-) (2). The former adds to the families of anionic [(Ge9R3)M(I)(Ge9R3)](-) (M(I) = Cu, Ag, and Au) as a neutral member and of the neutral [(Ge9R3)M(II)(Ge9R3)] (M(II) = Zn, Cd, and Hg), while the latter represents the first compound involving a metal from group 10.

Bi73-: the missing family member, finally isolated and characterized.

The synthesis and structure of Bi(7)(3-), the only missing member of the family of heptanuclear pnictogen cluster anions Pn(7)(3-) (Pn = pnictogen, a group 15 element excluding the unique nitrogen), is reported. The new species is synthesized by oxidation of a solution of K(5)Bi(4) by the solvent pyridine in the presence of (C(6)H(6))Cr(CO)(3). The existence of the species in solution is confirmed by electrospray mass spectrometry, while its structure is elucidated by single-crystal X-ray diffraction in the compound [K(2,2,2-crypt)](3)Bi(7)·2py (monoclinic, P2(1)/n, a = 13.8739(13) Å, b = 24.878(2) Å, c = 26.401(2) Å, ß = 96.353(4)°, V = 9056.5(14) Å(3), Z = 4, and R1/wR2 = 0.0636/0.1390 for the observed data and 0.0901/0.1541 for all data).

Synthesis, structures, and solution dynamics of tetrasubstituted nine-atom germanium deltahedral clusters.

Reported are the rational synthesis, structures, and solution dynamics of three tetrasubstituted and neutral Ge9-based deltahedral clusters [Ge9R3R'](0), where R = Si(SiMe3)3 and R' = Et (1), Sn(n)Bu3 (2), or Tl (3). The first step of the synthesis is a reaction of an acetonitrile suspension of the intermetallic precursor compound K4Ge9 with {Si(SiMe3)3}Cl which produces the trisubstituted monoanions [Ge9{Si(SiMe3)3}](-). A benzene suspension of the latter is then reacted with Sn(n)Bu3Cl or TlCp to produce 2 and 3, respectively, while the same acetonitrile solution is reacted with EtBr in order to produce 1. All three structures can be viewed as tricapped trigonal prisms of Ge9 with the three "hypersilyl" substituents, Si(SiMe3)3, exo-bonded to the capping atoms. The fourth substituent in 1, the ethyl group, is exo-bonded to one of the six available Ge atoms with the Ge-C bond positioned radially to the Ge9 core. In the case of 2, on the other hand, the tin fragment is found above one of the triangular bases of the prism interacting with one or more Ge atoms in three crystallographically different molecules in the structure. Lastly, the Tl atom in the structure of 3 is found capping a pseudosquare face between two hypersilyl substituents. NMR spectroscopy indicates that all three compounds are dynamic at room temperature. Variable-temperature studies suggest that the process in 1 and 2 is intramolecular while the process in 3 involves dissociation of the Tl(+) ion from the molecule followed by association at the same or another equivalent pseudosquare face of the molecule. Thus, the latter compound may be considered to a large extent to be ionic as it is made of a thallium cation and a trisubstituted cluster anion.

Trimetallic deltahedral Zintl ions [Sn(9-m-n)Ge(m)Bi(n)]((4-n)-) for n = 1-4 and m = 0-(9 - n): a theoretical survey with prediction and rationalization of the possible structures.

The recent discovery of trimetallic deltahedral Zintl ions based on Sn, Ge, and Bi revealed the possibility to obtain such clusters with a variety of different Sn/Ge/Bi ratios. Although only the dimer [(BiSn(6)Ge(2))-(Ge(2)Sn(6)Bi)](4-) was structurally characterized, a number of other nine-atom clusters with various stoichiometries were detected by electrospray mass spectrometry. The lack of structural data for the latter persuaded us to use relativistic density functional calculations in order to determine and rationalize theoretically the most stable structure conformation of each cluster and the positional preferences for the different atoms in the series [Sn(9-m-n)Ge(m)Bi(n)]((4-n)-) where n = 1-4 and m = 0-(9 - n). The analysis revealed strong dependence of the cluster geometry on the cluster stoichiometry and revealed sites with significantly different charge distribution. In addition, we introduce a parameter ϕ based on certain angles in order to rationalize the obtained structures as monocapped square antiprisms (C(4v)), tricapped trigonal prisms (D(3h)), or intermediates (C(2v)).

[Ge9{Si(SiMe3)3}3{SnPh3}]: a tetrasubstituted and neutral deltahedral nine-atom cluster.

Reaching neutral territory: The title compound, the first tetrasubstituted deltahedral Zintl cluster, is no longer an ion (see picture; Ge green, Si purple, Sn blue). It is a neutral molecule formed by a reaction of the trisilylated anion with Ph(3) SnCl.

Water compatibility and organic transformations of organo-Zintl deltahedral clusters.

We report the remarkable stability of di-substituted organo-Zintl deltahedral clusters in the presence of water. This has been exploited in a reaction at the organic substituents of the cluster which produces water as a by-product. Also reported are the synthesis, characterization, and crystal structure of [K-krypt](2)[Ge(9)-(CH=CH-CH(2)NH(2))(2)] involved in the reaction.

Tri-metallic deltahedral Zintl ions: experimental and theoretical studies of the novel dimer [(Sn6Ge2Bi)2]4-.

We report the synthesis, characterization, and computational rationalization of the first trimetallic deltahedral Zintl ions. The novel nine-atom clusters were structurally characterized as dimers of [(Sn(6)Ge(2)Bi)(2)](4-) with Ge-Ge intercluster bonds. They are synthesized either by reacting bimetallic clusters (Sn(9-x)Ge(x))(4-) with BiPh(3) or by direct extraction from precursors with nominal composition "K(4)Ge(4)Sn(4)Bi".

Rational synthesis of [Ge9{Si(SiMe3)3}3]- from its parent Zintl ion Ge9(4-).

Reported is the first rational synthesis of a trisubstituted deltahedral Zintl ion, [Ge(9){Si(SiMe(3))(3)}(3)](-) in this case, by the addition of the three substituents in a reaction of the parent naked deltahedral Zintl ion Ge(9)(4-) with {(Me(3)Si)(3)Si}Cl. The new species were crystallized and structurally characterized in [K(2,2,2-crypt)](2)[Ge(9){Si(SiMe(3))(3)}(3)] (monoclinic, P2(1)/c, a = 26.497(3) Å, b = 24.090(2) Å, c = 29.268(3) Å, ß = 113.888(2)°, V = 17082(3) Å(3), Z = 8, R1/wR2 = 0.0436/0.0812 for the observed data and 0.1023/0.1010 for all data).

Synthesis of nine-atom deltahedral Zintl ions of germanium and their functionalization with organic groups.

Although the first studies of Zintl ions date between the late 1890's and early 1930's they were not structurally characterized until many years later. Their redox chemistry is even younger, just about ten years old, but despite this short history these deltahedral clusters ions E9(n-) (E = Si, Ge, Sn, Pb; n = 2, 3, 4) have already shown interesting and diverse reactivity and have been at the forefront of rapidly developing and exciting new chemistry. Notable milestones are the oxidative coupling of Ge9(4-) clusters to oligomers and infinite chains, their metallation, capping by transition-metal organometallic fragments, insertion of a transition-metal atom at the center of the cluster which is sometimes combined with capping and oligomerization, addition of main-group organometallic fragments as exo-bonded substituents, and functionalization with various organic residues by reactions with organic halides and alkynes. This latter development of attaching organic fragments directly to the clusters has opened up a new field, namely organo-Zintl chemistry, that is potentially fertile for further synthetic explorations, and it is the step-by-step procedure for the synthesis of germanium-divinyl clusters described herein. The initial steps outline the synthesis of an intermetallic precursor of K4Ge9 from which the Ge9(4-) clusters are extracted later in solution. This involves fused-silica glass blowing, arc-welding of niobium containers, and handling of highly air-sensitive materials in a glove box. The air-sensitive K4Ge9 is then dissolved in ethylenediamine in the box and then alkenylated by a reaction with Me3SiC≡CSiMe3. The reaction is followed by electrospray mass spectrometry while the resulting solution is used for obtaining single crystals containing the functionalized clusters [H2C=CH-Ge9-CH=CH2](2-). For this purpose the solution is centrifuged, filtered, and carefully layered with a toluene solution of 18-crown-6. Left undisturbed for a few days, the so-layered solutions produced orange crystalline blocks of [K(18-crown-6)]2[Ge9(HCCH2))2]•en which were characterized by single-crystal X-ray diffraction. The process highlights standard reaction techniques, work-up, and analysis towards functionalized deltahedral Zintl clusters. It is hoped that it will help towards further development and understanding of these compounds in the community at large.

Hydrogen-bonded inclusion compounds with reversed polarity: anionic metal-complexes and cationic organic linkers.

Synthesized and structurally characterized is a new series of soft-host frameworks assembled by charge-assisted hydrogen bonds between an anionic metal complex (MC) and cationic organic linkers (OL), specifically [Co(en)(ox)(2)](-) and diprotonated 4,4'-bipyridinium (H(2)bpy) or 1,2-bis(4-pyridinium)ethylene (H(2)bpye). While frameworks built of cationic complexes and anionic organic linkers are already well-known, the seven new compounds described here represent the first series of frameworks with reversed polarity, that is, made of anionic complexes and cationic organic linkers. The compounds have a general formula [OL][MC](2)·n(guest), where the guest molecules 4,4'-biphenol (bp), 4-methoxyphenol (mp), 1,4-dimethoxybenzene (dmb), 1,6-dimethoxynaphtalene (dmn), and 4-nitroanisole (na). Structurally the compounds can be described as pillared-layer frameworks with layers constructed of MC anions and linked together by hydrogen-bonded cationic OL pillars. The guest molecules occupy the galleries between the pillars while their steric, electronic, and π-π and hydrogen-bonding capabilities influence the overall structure of the soft frameworks.

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)°, ß = 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)°, ß = 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, ß = 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, ß = 121.2140(10)°, V = 12523.5(15) Å(3), Z = 4).

"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-).

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.

The elusive closo-Ge(10)(2-) Zintl ion: finally "captured" as a ligand in the complex [Ge(10)Mn(CO)(4)](3-).

Although often seen in mass spectra, the otherwise elusive closo-Ge(10)(2-) Zintl ion has been finally structurally characterized as coordinated to manganese in [Ge(10)Mn(CO)(4)](3-) made by the reaction of nido-Ge(9)(4-) with Mn(2)(CO)(10) in ethylenediamine. The new cluster is a bicapped square antiprism, as expected for a closo-deltahedron of 10 atoms.

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.