Main Group Transition Metal Research Articles

Donor-acceptor activation of Carbon Dioxide.

The activation and functionalization of carbon dioxide entails great interest related to its abundance, low toxicity and associated environmental problems. However, the inertness of CO2 has posed a challenge towards its efficient conversion to added-value products. In this review we discuss one of the strategies that have been widely used to capture and activate carbon dioxide, namely the use of donor-acceptor interactions by partnering a Lewis acidic and a Lewis basic fragment. This type of CO2 activation resembles that found in metalloenzymes, whose outstanding performance in catalytically transforming carbon dioxide encourages further bioinspired research. We have divided this review into three general sections based on the nature of the active sites: metal-free examples (mainly formed by frustrated Lewis pairs), main group-transition metal combinations, and transition metal heterobimetallic complexes. Overall, we discuss one hundred compounds that cooperatively activate carbon dioxide by donor-acceptor interactions, revealing a wide range of structural motifs.

Entropic Control of Bonding, Guided by Chemical Pressure: Phase Transitions and 18-n+m Isomerism of IrIn3.

As with other electron counting rules, the 18-n rule of transition metal-main group (T-E) intermetallics offers a variety of potential interatomic connectivity patterns for any given electron count. What leads a compound to prefer one structure over others that satisfy this rule? Herein, we investigate this question as it relates to the two polymorphs of IrIn3: the high-temperature CoGa3-type and the low-temperature IrIn3-type forms. DFT-reversed approximation Molecular Orbital analysis reveals that both structures can be interpreted in terms of the 18-n rule but with different electron configurations. In the IrIn3 type, the Ir atoms obtain largely independent 18-electron configurations, while in the CoGa3 type, Ir-Ir isolobal bonds form as 1 electron/Ir atom is transferred to In-In interactions. The presence of a deep pseudogap for the CoGa3 type, but not for the IrIn3 type, suggests that it is electronically preferred. DFT-Chemical Pressure (CP) analysis shows that atomic packing provides another distinction between the structures. While both involve tensions between positive Ir-In CPs and negative In-In CPs, which call for the expansion and contraction of the structures, respectively, their distinct spatial arrangements create very different situations. In the CoGa3 type, the positive CPs create a framework that holds open large void spaces for In-based electrons (a scenario suitable for relatively small T atoms), while in the IrIn3 type the pressures are more homogenously distributed (a better solution for relatively large T atoms). The open spaces in the CoGa3 type result in quadrupolar CP features, a hallmark of low-frequency phonon modes and suggestive of higher vibrational entropy. Indeed, phonon band structure calculations for the two IrIn3 polymorphs indicate that the phase transition between them can largely be attributed to the entropic stabilization of the CoGa3-type phase due to soft motions associated with its CP quadrupoles. These CP-driven effects illustrate how the competition between global and local packing can shape how a structure realizes the 18-n rule and how the temperature can influence this balance.

Single Crystal Growth of Synthetic Sulfide- and Phosphide-Based Minerals for Physical Measurements

In this work, we review recent advances in the use of high-temperature solution growth that allow for the growth of single crystalline samples of synthetic minerals. We outline how low-melting binary or ternary solutions are attractive solvents for solution growth and provide examples of the growth of bismuthinite (Bi2S3), galena (PbS) and parkerite (Ni3Bi2S2). We then focus on the Rh-S, Pd-S and Ni-P phase spaces to discuss how the low-melting regions near transition metal-main group eutectic compositions make excellent solvents for crystal growth of several binary and ternary minerals containing both high melting and volatile elements as well as for the discovery of new materials. We end by discussing the growth of synthetic canfieldite (Ag8SnS6) and argyrodite (Ag8GeS6) from Ag2S–Sn-S-based solutions.

A Tour of Soft Atomic Motions: Chemical Pressure Quadrupoles Across Transition Metal–Main Group 1:2 Structure Types

The rational design of materials requires an understanding of the relationships between structure and properties. In some fields, advances in computational tools and modeling have mapped out many of these connections. In the realm of intermetallics, however, principles for such relationships are still needed. Recently, we illustrated how the DFT–Chemical Pressure (CP) analysis can link geometrical motifs within crystalline arrangements to the phonon band structures of intermetallics and thus the physical properties related to vibrations and atomic motion. The key indicators here are quadrupolar CP features─distributions in which positive and negative interatomic pressures are oriented perpendicular to one another. These quadrupoles then create low energy paths of motion for the atoms that can be linked to various structural phenomena, such as anisotropic vibrations and incommensurate modulations. In this article, we survey the presence of CP quadrupoles in a collection of TE2 structures (T = transition metal and E = main group element) and the roles they play in the behavior observed for these compounds. We begin by developing a metric for CP quadrupolar character, which can be calculated from the output of CP analysis. After compiling these metrics for 17 TE2 structure types, we delve deeper into four systems detected as exhibiting atomic sites with quadrupolar character: (1) the Co–Sn binary system, where the quadrupoles on the Co atoms in CuAl2-type CoSn2 direct the features of its superstructure in CoSn3; (2) arsenopyrite-type CoSb2, in which the highly quadrupolar CP distributions on the Sb atoms correlate with the motions followed during the phase transition to its high-temperature marcasite-type form; (3) the CrSi2 structure, in which the expansion of the lattice is predicted to open a helical path of potential soft motion analogous to that underlying the Nowotny Chimney Ladder series; and (4) the CdAs2 type, whose CP features anticipate the ability to incorporate Li atoms as guests. Together, these case studies highlight the potential for CP quadrupoles to link local atomic arrangements with a variety of emergent properties in intermetallic phases.

Synthesis of Tetrahedranes Containing the Unique Bridging Hetero-Dipnictogen Ligand EE' (E ≠ E'=P, As, Sb, Bi).

In order to improve and extend the rare class of tetrahedral mixed main group transition metal compounds, a new synthetic route for the complexes [{CpMo(CO)2}2(μ,η2:η2‐PE)] (E=As (1), Sb (2)) is described leading to higher yields and a decrease in reaction steps. Via this route, also the so far unknown heavier analogues containing AsSb (3 a), AsBi (4) and SbBi (5) ligands, respectively, are accessible. Single crystal X‐ray diffraction experiments and DFT calculations reveal that they represent very rare examples of compounds comprising covalent bonds between two different heavy pnictogen atoms, which show multiple bond character and are stabilised without any organic substituents. A simple one‐pot reaction of [CpMo(CO)2]2 with ME(SiMe3)2 (M=Li, K; E=P, As, Sb, Bi) and the subsequent addition of PCl3, AsCl3, SbCl3 or BiCl3, respectively, give the complexes 1–5. This synthesis is also transferable to the already known homo‐dipnictogen complexes [{CpMo(CO)2}2(μ,η2:η2‐E2)] (E=P, As, Sb, Bi) resulting in higher yields comparable to those in the literature reported procedures and allows the introduction of the bulkier and better soluble Cp′ (Cp′=tert butylcyclopentadienyl) ligand.

Systematic DFT Studies on Binary Pseudo-tetrahedral Zintl Anions: Relative Stabilities and Reactivities towards Protons, Trimethylsilyl Groups, and Iron Complex Fragments.

Binary pseudo‐tetrahedral Zintl anions composed of (semi)metal atoms of the p‐block elements have proven to be excellent starting materials for the synthesis of a variety of heterometallic and intermetalloid transition metal–main group metal cluster anions. However, only ten of the theoretically possible 48 anions have been experimentally accessed to date as isolable salts. This brings up the question whether the other species are generally not achievable, or whether synthetic chemists just have not succeeded in their preparation so far. To contribute to a possible answer to this question, global minimum structures were calculated for all anions of the type (TrTt3)5−, (TrPn3)2−, and (Tt2Pn2)2−, comprising elements of periods 3 to 6 (Tr: triel, Al⋅⋅⋅Tl; Tt: tetrel, Si⋅⋅⋅Pb; Pn: pnictogen, P⋅⋅⋅Bi). By analyzing the computational results, a concept was developed to predict which of the yet missing anions should be synthesizable and why. Additionally, the results of an electrophilic attack by protons or trimethylsilyl groups or a nucleophilic attack by transition metal complex fragments are described. The latter yields butterfly‐like structures that can be viewed as a new form of adaptable tridentate chelating ligands.

Computational Study of Methane C-H Activation by Main Group and Mixed Main Group-Transition Metal Complexes.

In the present density functional theory (DFT) research, nine different molecules, each with different combinations of A (triel) and E (divalent metal) elements, were reacted to effect methane C–H activation. The compounds modeled herein incorporated the triels A = B, Al, or Ga and the divalent metals E = Be, Mg, or Zn. The results show that changes in the divalent metal have a much bigger impact on the thermodynamics and methane activation barriers than changes in the triels. The activating molecules that contained beryllium were most likely to have the potential for activating methane, as their free energies of reaction and free energy barriers were close to reasonable experimental values (i.e., ΔG close to thermoneutral, ΔG‡ ~30 kcal/mol). In contrast, the molecules that contained larger elements such as Zn and Ga had much higher ΔG‡. The addition of various substituents to the A–E complexes did not seem to affect thermodynamics but had some effect on the kinetics when substituted closer to the active site.

Templating Structural Progessions in Intermetallics: How Chemical Pressure Directs Helix Formation in the Nowotny Chimney Ladders.

In the structural diversity of intermetallic phases, hierarchies can be perceived relating complex structures to relatively simple parent structures. One example is the Nowotny Chimney Ladder (NCL) series, a family of transition metal-main group (T-E) compounds in which the T sublattices trace out helical channels populated by E-atom helices. A sequence of structures emerges from this arrangement because the spacing along the channels of the E atoms smoothly varies relative to that of the T framework, dictated largely by optimization of the valence-electron concentration. In this Communication, we show how this behavior is anticipated and explained by the Density Functional Theory-Chemical Pressure (DFT-CP) schemes of the NCLs. A CP analysis of the RuGa2 parent structure reveals CP quadrupoles on the Ga atoms (telltale signs of soft atomic motion) that arise from overly short Ru-Ga contacts along one axis and underutilized spaces in the perpendicular directions. In their placement and orientation, the CP quadrupoles highlight a helical path of facile movement for the Ga atoms that avoids further compression of the already strained Ru-Ga contacts. The E atoms of a series of NCLs (in their DFT-optimized geometries) are all found to lie along this helix, with the CP quadrupole character being a persistent feature. In this way, the T sublattice common to the NCLs encodes helical paths by which the E-atom spacing can be varied, creating a mechanism to accommodate electronically driven compositional changes. These results illustrate how CP schemes can be combined with electron-counting rules to create well-defined structural sequences, potentially guiding the discovery of new intermetallic phases.

Predissociation Measurements of Bond Dissociation Energies.

A fundamental need in chemistry is understanding the chemical bond, for which the most quantitative measure is the bond dissociation energy (BDE). While BDEs of chemical bonds formed from the lighter main group elements are generally well-known and readily calculated by modern computational chemistry, chemical bonds involving the transition metals, lanthanides, and actinides remain computationally extremely challenging. This is due to the simultaneous importance of electron correlation, spin-orbit interaction, and other relativistic effects, coupled with the large numbers of low-lying states that are accessible in systems with open d or f subshells. The development of efficient and accurate computational methods for these species is currently a major focus of the field. An obstacle to this effort has been the scarcity of highly precise benchmarks for the BDEs of M-X bonds. For most of the transition metal, lanthanide, or actinide systems, tabulated BDEs of M-X bonds have been determined by Knudsen effusion mass spectrometric measurements of high-temperature equilibria. The measured ion signals are converted to pressures and activities of the species involved in the equilibrium, and the equilibrium constants are then analyzed using a van't Hoff plot or the third-law method to extract the reaction enthalpy, which is extrapolated to 0 K to obtain the BDE. This procedure introduces errors at every step and ultimately leads to BDEs that are typically uncertain by 2-20 kcal mol-1 (0.1-1 eV). A second method in common use employs a thermochemical cycle in which the ionization energies of the MX molecule and M atom are combined with the BDE of the M+-X bond, obtained via guided ion beam mass spectrometry, to yield the BDE of the neutral, M-X. When accurate values of all three components of the cycle are available, this method yields good results-but only rarely are all three values available. We have recently implemented a new method for the precise measurement of BDEs in molecules with large densities of electronic states that is based on the rapid predissociation of these species as soon as the ground separated atom limit is exceeded. When a sharp predissociation threshold is observed, its value directly provides the BDE of the system. With this method, we are able in favorable cases to determine M-X BDEs to an accuracy of ∼0.1 kcal mol-1 (0.004 eV). The method is generally applicable to species that have a high density of states at the ground separated atom limit and has been used to measure the BDEs of more than 50 transition metal-main group MX molecules thus far. In addition, a number of metal-metal BDEs have also been measured with this method. There are good prospects for the extension of the method to polyatomic systems and to lanthanide and actinide-containing molecules. These precise BDE measurements provide chemical trends for the BDEs across the transition metal series, as well as crucial benchmarks for the development of efficient and accurate computational methods for the d- and f-block elements.

Parallels in Structural Chemistry between the Molecular and Metallic Realms Revealed by Complex Intermetallic Phases.

The structural diversity of intermetallic phases poses a great challenge to chemical theory and materials design. In this Account, two examples are used to illustrate how a focus on the most complex of these structures (and their relationships to simpler ones) can reveal how chemical principles underlie structure for broad families of compounds. First, we show how experimental investigations into the Fe-Al-Si system, inspired by host-guest like features in the structure of Fe25Al78Si20, led to a theoretical approach to deriving isolobal analogies between molecular and intermetallic compounds and a more general electron counting rule. Specifically, the Fe8Al17.6Si7.4 compound obtained in these syntheses was traced to a fragmentation of the fluorite-type structure (as adopted by NiSi2), driven by the maintenance of 18-electron configurations on the transition metal centers. The desire to quickly generalize these conclusions to a broader range of phases motivated the formulation of the reversed approximation Molecular Orbital (raMO) approach. The application of raMO to a diverse series of compounds allowed us recognize the prevalence of electron pair sharing in multicenter functions isolobal to classical covalent bonds and to propose the 18 - n electron rule for transition metal-main group (T-E) intermetallic compounds. These approaches provided a framework for understanding the 14-electron rule of the Nowotny Chimney Ladder phases, a temperature-driven phase transition in GdCoSi2, and the bcc-structure of group VI transition metals. In the second story, we recount the development of the chemical pressure approach to analyzing atomic size and packing effects in intermetallic structures. We begin with how the stability of the Yb2Ag7-type structure of Ca2Ag7 over the more common CaCu5 type highlights the pressing need for approaches to assessing the role of atomic size in crystal structures, and inspired the development of the DFT-Chemical Pressure (CP) method. Examples of structural phenomena elucidated by this approach are then given, including the Y/Co2 dumbbell substitution in the Th2Zn17-type phase Y2Co17, and local icosahedral order in the Tsai-type quasicrystal approximant CaCd6. We next discuss how deriving relationships between the CP features of a structure and its phonon modes provided a way of both validating the method and visualizing how local arrangements can give rise to soft vibrational modes. The themes of structural mechanisms for CP relief and soft atomic motions merge in the discovery and elucidation of the incommensurately modulated phase CaPd5. In the conclusion of this Account, we propose combining raMO and CP methods for focused predictions of structural phenomena.

Lanthanide Inorganic Solids Based on Main Group Borates and Oxyanions of Lone Pair Cations

ABSTRACTLanthanide borates containing post transition metal main group elements, including Ga(III), Ge(IV), Sb(V) and Te(VI), as well as lanthanide salts of the oxyanions of lone pair cations, such as I(V), Se(IV) and Te(IV), were reviewed. The post transition metal main group elements in lanthanide borates adopt octahedral or tetrahedral geometry only. In the structure of lanthanide galloborates, only octahedral GaO6 was found while both octahedral GeO6 and tetrahedral GeO4 appeared in borogermanates. The fifth period elements Sb(V) and Te(VI) prefer octahedral coordination geometry in lanthanide borates system. The second groups introduced to lanthanide oxyanions of lone pairs are mainly focused on d0 TM units, such as WO4 tetrahedron, VO5 square pyramid or MoO6 octahedron, and rigid tetrahedral groups like sulfate SO4, silica SiO4 or selenate SeO4 units. Divalent cations like Pb(II) and magnetic ions of Cu(II) or Mn(II) were also included. The structure chemistry of lanthanide ions in these systems is rich. Coordination numbers from six to ten are discovered, yielding a wide range of coordination geometries including the pentagonal bipyramid, square antiprism, metabidiminished icosahedron, tricapped trigonal prism, capped triangular cupola, etc. The connectivity modes between the Ln polyhedra are miscellaneous, from 3D network, to 2D layer, 1D chain, tetramer, trimer, dimer and finally monomer. A number of compounds display NCS structures and strong SHG response, and many lanthanide compounds exhibit good luminescent properties in visible and IR region.

Prediction of Novel High-Pressure Structures of Magnesium Niobium Dihydride.

On the basis of a combination of the particle-swarm optimization technique and density functional theory (DFT), we explore the crystal structures of MgH2, NbH2, and MgNbH2 under high pressure. The enthalpy-pressure (H-P) diagrams indicate that the structural transition sequence of MgH2 is α → γ → δ → ε → ζ and that NbH2 transforms from the Fm3̅m phase to the Pnma phase at 47.80 GPa. However, MgNbH2 is unstable when the pressure is too low or too high. Two novel MgNbH2 structures, the hexagonal P6̅m2 phase and the orthorhombic Cmcm phase, are discovered, which are stable in the pressure ranges of 13.24-128.27 GPa and 128.27-186.77 GPa, respectively. The P6̅m2 phase of MgNbH2 consists of alternate layers of polymetric NbH6 and MgH6 triangular prisms, while the Cmcm phase contains distorted MgH6 trigonal prisms. The calculated elastic constants and phonon dispersions confirm that both phases are mechanically and dynamically stable. The analyses of density of states (DOS), electron localization function (ELF), and Bader charge demonstrate that a combination of ionic and metallic bonds exist in both P6̅m2 and Cmcm phases. We hope the newly predicted magnesium niobium dihydrides with desirable electronic properties will promote future experimental and theoretical studies on mixed main group-transition metal hydrides.

Electron-counting in intermetallics made easy: the 18-n rule and isolobal bonds across the Os–Al system

Abstract Electron count is one of the key factors controlling the formation of complex intermetallic structures. The delocalized nature of bonding in metals, however, has made it difficult to connect these electron counts to the various structural features that make up complex intermetallics. In this article, we illustrate how structural progressions in transition metal-main group intermetallics can in fact be simply understood with the 18-n bonding scheme, using as an example series the four binary phases of the Os–Al system. Our analysis begins with the CsCl-type OsAl phase, whose 11 electrons/Os count is one electron short of that predicted by the 18-n rule. This electron deficiency provides a driving force for Al incorporation to make more Al-rich intermetallic phases. In the structures of Os2Al3 (own type) and OsAl2 (MoSi2 type), each additional Al atom contributes three electrons, two of which go towards cleaving Os–Os isolobal bonds, with the third alleviating the original electron deficiency of OsAl. Across the series, the framework of isolobal Os–Os bonds is reduced from a primitive cubic network (n=6, OsAl) to layers of cubes (n=5, Os2Al3) to individual square nets (n=4, OsAl2). Upon adding more Al to form Os4Al13, the Os–Os contacts are further reduced to dumbbells at the interfaces between fluorite-type columns. At this point, the added Al raises the electron count beyond that needed for filled octadecets on the Os atoms; the excess electrons are accommodated by Al–Al bonds. Throughout this work, we emphasize how the 18-n scheme can be applied from structural inspection alone, with theoretical calculations confirming or refining these conclusions.

Mixed main group transition metal clusters: Reactions of [Ru3(CO)10(μ-dppm)] with Ph3SnH

Novel dppm-ligated ruthenium-tin clusters have been prepared from the reaction of [Ru3(CO)10(μ-dppm)] with Ph3SnH. At room temperature and in the presence of Me3NO, [Ru3(CO)9(SnPh3) (μ-dppm) (μ-H)] (1) is produced from the formal loss of CO and Sn-H bond oxidative-addition. Treatment of 1 with a further two equivalents of Ph3SnH (in the presence of Me3NO) gave [Ru3(CO)7(SnPh3)2(μ-SnPh2)(μ-dppm)(μ-H)(μ3-H)] (2) which results from both Sn–H and Sn–C bond scission and contains two different hydride environments (μ and μ3) and a μ-SnPh2 moiety. Cluster 2 has 48 CVE (cluster valence electron) with three formal ruthenium-ruthenium bonds; two of those are very long and fall at the extreme end of distances attributed to ruthenium-ruthenium bonds. Thermolysis of 2 at 66 °C liberates benzene to give [Ru3(CO)8(SnPh3)(μ-SnPh2)(μ3-SnPh2)(μ-dppm)(μ-H)] (3). DFT calculations confirm that the hydride bridges one of the Ru-μ-SnPh2 bonds in 3. The solid-state structures of 2 and 3 have been determined by X-ray crystallography, and the bonding and ligand distribution have been investigated by DFT studies. The geometry-optimized structures are consistent with the solid-state structures.

Mixed-Ligand Approach to Changing the Metal Ratio in Bismuth-Transition Metal Heterometallic Precursors.

A new series of heteroleptic bismuth-transition metal β-diketonates [BiM(hfac)3(thd)2] (M = Mn (1), Co (2), and Ni (3); hfac = hexafluoroacetylacetonate, thd = tetramethylheptanedionate) with Bi:M = 1:1 ratio have been synthesized by stoichiometric reactions between homometallic reagents [Bi(III)(hfac)3] and [M(II)(thd)2]. On the basis of analysis of the metal-ligand interactions in heterometallic structures, the title compounds were formulated as ion-pair {[Bi(III)(thd)2](+)[M(II)(hfac)3](-)} complexes. The direct reaction between homometallic reagents proceeds with a full ligand exchange between main group and transition metal centers, yielding dinuclear heterometallic molecules. In heteroleptic molecules 1-3, the Lewis acidic, coordinatively unsaturated Bi(III) centers are chelated by two bulky, electron-donating thd ligands and maintain bridging interactions with three oxygen atoms of small, electron-withdrawing hfac groups that chelate the neighboring divalent transition metals. Application of the mixed-ligand approach allows one to change the connectivity pattern within the heterometallic assembly and to isolate highly volatile precursors with the proper Bi:M = 1:1 ratio. The mixed-ligand approach employed in this work opens broad opportunities for the synthesis of heterometallic (main group-transition metal) molecular precursors with specific M:M' ratio in the case when homoleptic counterparts either do not exist or afford products with an incorrect metal:metal ratio for the target materials. Heteroleptic complexes obtained in the course of this study represent prospective single-source precursors for the low-temperature preparation of multiferroic perovskite-type oxides.

One frontier of the rare-earth organometallic chemistry: The chemistry of rare-earth metal alkylidene, imido and phosphinidene complexes

The transition metal complexes, which contain M=E (E = C, N, P) double bond, are very important. Not only the understanding of the nature of transition metal-main group element double bond is of fundamental concern, but also these complexes have some excellent and unique reactivities. Rare-earth metal alkyl, amide and phosphide complexes have been extensively studied during the last three decades. However, the chemistry of rare-earth metal alkylidene, imido and phosphinidene complexes remain challenging. The efforts in this field led to some bridged alkylidene, imido and phosphinidene complexes, and phosphorus-stabilized “pincer” type alkylidene complexes. Although these reported complexes are different from their “terminal” cousins, which contain M=E (E = C, N, P) double bond, they shed light on the exploration to rare-earth metal terminal alkylidene, imido and phosphinidene complexes. This paper covers the synthesis, structures and reactivities of the bridged alkylidene, imido and phosphinidene complexes, phosphorus-stabilized “pincer” type alkylidene complexes as well as a recent breakthrough in the rare-earth metal terminal imido complexes.

Selective Insertion of Oxygen and Selenium into an Electron-Precise Paramagnetic Selenium−Manganese Carbonyl Cluster [Se6Mn6(CO)18]4−

The facile synthesis of a novel electron-precise paramagnetic hexamanganese carbonyl selenide cluster [Se(6)Mn(6)(CO)(18)](4-) (1) was discovered, which demonstrates contrasting reactivity toward O(2) and Se(8) under markedly mild conditions to afford the O- and Se-inserted clusters [Se(6)Mn(6)(CO)(18)(O)](4-) (2) and [Se(10)Mn(6)(CO)(18)](4-) (3), respectively. Clusters 1-3 represent the first examples of electron-precise paramagnetic main-group transition metal carbonyl clusters, and their formation and bonding properties are further elucidated by theoretical calculations.

On the nature of the transition metal–main group metal bond: synthesis and theoretical calculations on iridium gallyl complexes

The iridum-gallyl complex MeIr(PCy(3))(2)(GaMe(2))(Cl*GaMe(3)) exhibits a short Ir-Ga bond length of 2.381(1)-2.389(2) Å. Theoretical calculations (ZORA BP86/TZ2P) support the presence of a Ir-Ga single bond but highlight a π orbital contribution.

Au3SnCuP10 and Au3SnP7: Preparation and Crystal Structures of Au3Sn Heterocluster Polyphosphides.

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Au3SnCuP10 and Au3SnP7: Preparation and Crystal Structures of Au3Sn Heterocluster Polyphosphides

The formation of Au3Sn heteroclusters completes the homologous series of M3Sn clusters observed for transition metal main-group polyphosphides. Au3SnCuP10 is cubic, space group F4̅3̅m (No. 216) with lattice parameter a = 10.3953(5) Å . The structure refinement yielded R1 = 0.0353 and wR2 = 0.0726 for 154 F2 values and 13 variables. Disordered Au3Sn heteroclusters occupy all octahedral, and adamantane like P10 cages one half of the tetrahedral voids of a face-centred cubic ( fcc) arrangement of copper. Ordered and orientationally disordered Au3Sn heteroclusters have been observed for Au3SnP7, embedded in a 1 ∞ [P7] polyphosphide unit formed by six-membered phosphorus rings in chair conformation which are linked by a P-bridge. Au3SnP7 is monoclinic, space group P21/m (No. 11) with lattice parameters of a = 6.219(2), b = 10.836(2), c = 6.318(2) Å , β = 108.65(2)°, V = 403.4(2) Å3, R1 = 0.0412 and wR2 = 0.0745, 1261 F2 values and 56 variables. Au3SnP7 with disordered Au3Sn clusters has slightly larger lattice parameters of a = 6.343(3), b = 10.955(3), c = 6.372(3) Å , β = 108.63(2)°, V = 419.6(2) Å3, R1 = 0.0324 and wR2 = 0.0691, 1131 F2 values and 58 variables.