Three-center Bonds Research Articles

Three new amidophosphoric acid esters with a P(O)[OCH2C(CH3)2CH2O] segment: X-ray diffraction, DFT, AIM and Hirshfeld surface investigations of bi- and tri-furcated (three and four-center) hydrogen bond interactions

AbstractStructural and packing features of three new amidophosphoric acid esters having a common partXP(O)[OCH2C(CH3)2CH2O], withX = [(CH3)3CNH] (1), [(CH3)2HCNH] (2) and [C6H11(CH3)N] (3), are investigated by single crystal X-ray diffraction. The results illustrate that the compounds1and3crystallize with one independent molecule in the asymmetric unit; whereas, for2, the compound crystallizes with three independent molecules in the asymmetric unit. The crystal structures are mostly stabilizedviatri-furcated hydrogen bond interactions (C–H · · ·)2(N–H · · ·)O=P in1and (C–H · · ·)3O=P in3, while the stability is given by bi-furcated hydrogen bond interactions (C–H · · ·)(N–H · · ·)O=P in2. For a better understanding of the nature, strength and energetics associated with the formation of the quoted multi-center hydrogen bond interactions, the Natural Bond Order (NBO) method from Density Functional Theory (DFT) and a topological analysis by means of Atoms In Molecules (AIM) and Hirshfeld surface procedures were performed. These studies reveal that the studied multi-center hydrogen bond interactions of the type O · · · H are favoured in the crystal packing displaying enrichment ratios larger than unity. The detailed nature of the different interactions in these multi-center interactions is studied for the first time in such compounds. It is shown that the N–H · · · O interaction is rather non-covalent closed-shell whereas the C–H · · · O interaction is more van der Waals closed-shell. Stronger hydrogen bond interactions are observed for a lower multiple H-atom acceptor oxygen in three-center hydrogen bond interactions (C–H · · ·)(N–H · · ·)O=P of2than for four-center interactions in1[i.e. (C–H · · ·)2(N–H · · ·)O=P] and3[i.e. (C–H · · ·)3O=P]. The better H-atom acceptability of the O atom of P=O compared with the esteric O atom is explained by the richers-character of the hybrid orbital of the O atom acceptor of P=O coupled with enhance of the polarization and charge. The obtained results are also confirmed by Molecular Electrostatic Potential (MEP).

Iodonium Polyiodide Crystals in the Framework of Periodic Calculations with Localized Atomic Basis Sets

Methodological features of the crystal structure modeling for compounds with three-center halogen bond formed by two electron donors S–I+–S in polyiodide crystals were considered within the framework of periodic calculations based on localized atomic orbitals. The analysis of applying the different basis sets, effective core potentials, density functional theory functionals, and Grimme dispersion corrections revealed their effect on the geometric, electronic and vibrational properties obtained in calculations. Distribution of S-I bond lengths in S–I+–S fragment was analyzed. The effect of hybrid functional was demonstrated in the significant elongation of S-I distance. The treatment of dispersion interactions via Grimme approach did not significantly influence obtained results. The calculated vibration modes in medium wavenumber region of characteristic cationic stretching vibrations were validated according to experimental Raman spectra and were found to be in good agreement for C-N, C-C and C=S stretching vibrations. Small-core effective potential was shown to be effective for representation of bond lengths in S–I+–S fragment and gave reasonable results for vibrational data for cationic stretching vibrations. Taking into account relativistic effect on the level of basis set led to fine reproducibility of S-I bond lengths although in polyiodides of complex structure it should be treated with caution due to possible incorrect representation of interanionic distances.

Hydrogen inserted into the Si(100)-2 × 1-H surface: a first-principles study.

Hydrogen can be inserted into Si(100)-2 × 1-H during surface preparation or during the hydrogen desorption lithography used to create atomic-scale devices. Here, a hydrogen atom inserted into a hydrogen monolayer on the Si(100)-2 × 1 surface has been studied using density functional theory. Hydrogen-induced defects were considered in their neutral, negative, and positive charge states. It was found that hydrogen forms a dihydride unit on the surface in the most stable neutral and negative charge states. Hydrogen located in the groove between dimer rows is also one of the most stable negative charge states. In the positive charge state, hydrogen forms a three-center bond inside a Si dimer, Si-H-Si, similar to the bulk case. A comparison of simulated scanning tunneling microscopy (STM) images with the experimental data available in the literature showed that neutral and negatively charged hydrogen-induced defects were already observed in experiments. The results reveal that the H atom inserted into a hydrogen monolayer on the Si(100)-2 × 1 surface can lead to the formation of a positively or negatively charged defect. It is shown that H atoms in the considered configurations can play a role in various surface reactions.

Synthesis and Study of Derivatives of the [B10H10]2– Anion with Amino Acids

The interaction between tetrahydrofuran, tetrahydropyran, and 1,4-dioxane derivatives of the [B10H10]2– anion and a number of amino acids (glycine, cysteine, serine, and p-aminobenzoic acid) has been studied. It has been shown that, during the reactions, the exo-polyhedral cyclic substituent is opened to form closo-decaborates containing the pendant amino acid group, while the nucleophilic reagent is attached via the oxygen atom. The nucleophilic reagents can be both amino acids (in water) and their sodium salts (in dimethylformamide). All the compounds obtained are effective polydentate ligands capable to be coordinated to the metal through the donor atoms of the amino acid moiety attached and by forming three-center two-electron bonds. The synthesized compounds have been studied by elemental analysis, IR spectroscopy, 11B, 13C, and 1H NMR spectroscopies, and ESI mass spectrometry. closo-Decaborates with pendant amino acid moieties are of interest for 10B neutron capture therapy of malignant tumors due to the high content of boron atoms and a convenient way to transport them to the cells affected.

Reduction of carbon and nitrogen centered trigonal prismatic tungsten clusters: Bonding patterns as viewed by ELF and AIM methods

WW and WX bonds in a series of trigonal prismatic [X@W6Cl18]n (n = 0, −2, −4 for X = C; n = 1, −1, −3 for X = N) clusters were studied using the methods of Electron Localization Function (ELF) and the Atoms In Molecules (AIM) along with the molecular orbital (MO) approach. The [X@W6Cl18]n clusters contain two {W3} fragments which form a trigonal prism. Each {W3} fragment is characterized by a three-center bond and three two-center bonds. The carbon or the nitrogen atom encapsulated in the center of the trigonal prism influence intertriangular WW bonds. The bonding pattern of {W3} fragments are preserved even in four-electron reduced clusters. The inter-triangular bonding is mainly due to the interactions of two tungsten atoms with the central C or N atom and is associated with the formation of a heteroatomic three-center bond.

Quantum information-based analysis of electron-deficient bonds.

Recently, the correlation theory of the chemical bond was developed, which applies concepts of quantum information theory for the characterization of chemical bonds, based on the multiorbital correlations within the molecule. Here, for the first time, we extend the use of this mathematical toolbox for the description of electron-deficient bonds. We start by verifying the theory on the textbook example of a molecule with three-center two-electron bonds, namely, diborane(6). We then show that the correlation theory of the chemical bond is able to properly describe the bonding situation in more exotic molecules which have been synthesized and characterized only recently, in particular, the diborane molecule with four hydrogen atoms [diborane(4)] and a neutral zerovalent s-block beryllium complex, whose surprising stability was attributed to a strong three-center two-electron π bond stretching across the C-Be-C core. Our approach is of high importance especially in the light of a constant chase after novel compounds with extraordinary properties where the bonding is expected to be unusual.

Ligand metathesis in copper(I) complex [Cu2(CH3CN)4[B10H10]] to form [Cu2L4[B10H10]] (L = Ph3P, 5Nphen)

In this work, copper(I) complexation proceeding in the [Cu2(CH3CN)4[B10H10]]/CH3CN/L system (L = triphenylphosphine (Ph3P) and 5N-phenanthridine (5Nphen)) has been studied. The metathesis of acetonitrile molecules in complex [Cu2(CH3CN)4[B10H10]] with L molecules to form [Cu2L4[B10H10]] is considered for the first time. We believe that the process proceeds stepwise through the formation of intermediate mixed-ligand complexes [Cu2(CH3CN)4 –nLn[B10H10]] (n = 1, 2, 3). Complexes [Cu2(Ph3P)2(CH3CN)2[B10H10]], [Cu2(Ph3P)2(CH3CN)2[B10H10]]·CH3CN, [Cu2(CH3CN)(5Nphen)3[B10H10]], and [Cu2(5Nphen)4[B10H10]]·5Nphen have been synthesized and characterized by IR spectroscopy, elemental analysis, and X-ray diffraction (CCDC 1898291–18998294). In the compounds studied, three-center two-electron CuHB bonds are formed between metal atoms and boron cluster anions.

A Continuum from Halogen Bonds to Covalent Bonds: Where Do λ3 Iodanes Fit?

The intrinsic bonding nature of λ 3 -iodanes was investigated to determine where its hypervalent bonds fit along the spectrum between halogen bonding and covalent bonding. Density functional theory with an augmented Dunning valence triple zeta basis set ( ω B97X-D/aug-cc-pVTZ) coupled with vibrational spectroscopy was utilized to study a diverse set of 34 hypervalent iodine compounds. This level of theory was rationalized by comparing computational and experimental data for a small set of closely-related and well-studied iodine molecules and by a comparison with CCSD(T)/aug-cc-pVTZ results for a subset of the investigated iodine compounds. Axial bonds in λ 3 -iodanes fit between the three-center four-electron bond, as observed for the trihalide species IF 2 − and the covalent FI molecule. The equatorial bonds in λ 3 -iodanes are of a covalent nature. We explored how the equatorial ligand and axial substituents affect the chemical properties of λ 3 -iodanes by analyzing natural bond orbital charges, local vibrational modes, the covalent/electrostatic character, and the three-center four-electron bonding character. In summary, our results show for the first time that there is a smooth transition between halogen bonding → 3c–4e bonding in trihalides → 3c–4e bonding in hypervalent iodine compounds → covalent bonding, opening a manifold of new avenues for the design of hypervalent iodine compounds with specific properties.

Spectroscopic and Quantum Chemical Investigation of Benzene-1,2-dithiolate-Coordinated Diiron Complexes with Relevance to Dinitrogen Activation.

In this work, a benzene-1,2-dithiolate (bdt) pentamethylcyclopentadienyl di-iron complex [Cp*Fe(μ-η2:η4-bdt)FeCp*] and its [Cp*Fe(bdt)(X)FeCp*] analogues (where X = N2H2, N2H3-, H-, NH2-, NHCH3-, or NO+) were investigated through spectroscopic and computational studies. These complexes are of relevance as model systems for dinitrogen activation in nitrogenase and share with its active site the presence of iron, sulfur ligands, and a very flexible electronic structure. On the basis of a combination of X-ray emission spectroscopy (XES), X-ray crystallography, Mössbauer, NMR, and EPR spectroscopy, the geometric and electronic structure of the series has been experimentally elucidated. All iron atoms were found to be in a local low-spin configuration. When no additional X ligand is bound, the bdt ligand is tilted and features a stabilizing π-interaction with one of the iron atoms. The number of lone-pair orbitals provided by the nitrogen-containing species is crucial to the overall electronic structure. When only one lone-pair is present and the iron atoms are bridged by one atom, a three-center bond occurs, and a direct Fe-Fe bond is absent. If the bridging atom provides two lone-pairs, then an Fe-Fe bond is formed. A recurring theme for all ligands is σ-donation into the unoccupied eg manifolds of both iron atoms and back-donation from the t2g manifolds into the ligand π* orbitals. The latter results in a weakening of the double bond of the bound ligand, and in the case of NO+, it results in a weakening of all bonds that comprise triple bond. The electron-rich thiolates further amplify this effect and can also serve as bases for proton binding. While the above observations have been made for the studied di-iron complexes, they may be of relevance for the active site in nitrogenase, where a similar N2 binding mode may occur allowing for the simultaneous weakening of the N2 σ bond and π bonds.

THE METHOD FOR OBTAINING A DERIVATIVE CLOSO-DECABORATE ANION WITH PENDANTE DTPA-GROUP

This paper describes the method for obtaining a new derivative of the closo-decaborate anion with diethylenetriaminepentaacetic acid (DTPA) as a pendant group attached to the boron cluster through an alkoxyl spacer chain. This derivative is formed by the interaction of 1,4-dioxane derivative of the anion [B10H10]2- with DTPA potassium salt in an aqueous medium. As a result of the reaction, an exo-polyhedral cyclic substituent is opened, and then the addition of a polyfunctional group through an oxygen atom occurs. The synthesized compound is in fact an effective polydentate ligand capable of coordinating to the complexing agent both due to the donor atoms of the attached DTPA fragment and through the formation of three-center two-electron bonds. The obtained compound interacts with gadolinium(III) carbonate forming a complex of the composition [Gd2B10H9O2C4H8(dtpa)]·3H2O. The synthesized substances were studied by IR spectroscopy, polynuclear (11B, 13C and 1H) NMR spectroscopy, ESI mass spectrometry, elemental and thermographic analysis. closo-Decaborate with the pendant DTPA group is of interest in 10B neutron capture therapy of malignant tumors due to the high content of boron atoms and a convenient way of their transport to the affected cells. The obtained boron-containing derivatives of gadolinium(III) can act as drugs of combined action, because they can perform, in addition to the above described therapeutic function, the diagnostic function due to the presence of gadolinium atoms int hem.

Halogen Bond Asymmetry in Solution.

Halogen bonding is the noncovalent interaction of halogen atoms in which they act as electron acceptors. Whereas three-center hydrogen bond complexes, [D···H···D]+ where D is an electron donor, exist in solution as rapidly equilibrating asymmetric species, the analogous halogen bonds, [D···X···D]+, have been observed so far only to adopt static and symmetric geometries. Herein, we investigate whether halogen bond asymmetry, i.e., a [D–X···D]+ bond geometry, in which one of the D–X bonds is shorter and stronger, could be induced by modulation of electronic or steric factors. We have also attempted to convert a static three-center halogen bond complex into a mixture of rapidly exchanging asymmetric isomers, [D···X–D]+ ⇄ [D–X···D]+, corresponding to the preferred form of the analogous hydrogen bonded complexes. Using 15N NMR, IPE NMR, and DFT, we prove that a static, asymmetric geometry, [D–X···D]+, is obtained upon desymmetrization of the electron density of a complex. We demonstrate computationally that conversion into a dynamic mixture of asymmetric geometries, [D···X–D]+ ⇄ [D–X···D]+, is achievable upon increasing the donor–donor distance. However, due to the high energetic gain upon formation of the three-center-four-electron halogen bond, the assessed complex strongly prefers to form a dimer with two static and symmetric three-center halogen bonds over a dynamic and asymmetric halogen bonded form. Our observations indicate a vastly different preference in the secondary bonding of H+ and X+. Understanding the consequences of electronic and steric influences on the strength and geometry of the three-center halogen bond provides useful knowledge on chemical bonding and for the development of improved halonium transfer agents.

Aromaticity of Bare Iridium Trimers and Ir3M0/+ and $$\rm{Ir}_3M_2^{+/3+}$$ I r 3 M 2 + / 3 + (M = Li, Na, K, and Be, Ca) Bimetallic Clusters

The structural stabilities, bonding nature, electronic properties, and aromaticity of bare iridium trimers $$\rm{Ir}_3^{+/-}$$ with different geometries and spin multiplicities are studied at the DFT/B3LYP level of theory. The ground state of the $$\rm{Ir}_3^{+}$$ cation is found to be the 3A2 (C2v) triplet state and the ground state of the $$\rm{Ir}_3^{-}$$ anion the 5A2 (C2v) quintet state. A detailed molecular orbital (MO) analysis indicates that the ground-state $$\rm{Ir}_3^{+}$$ ion (C2v, 3A2) possesses double (σ and partial δ) aromaticity as well as the ground-state $$\rm{Ir}_3^{-}$$ ion (C2v, 5A2). The multiple d-orbital aromaticity is responsible for the totally delocalized three-center metal-metal bond of the triangular Ir3 framework. $$\rm{Ir}_3^{-}$$ (C2v, 1A1) structure motif is perfectly preserved in pyramidal Ir3M0/+ (Cs, 1A′) and bipyramidal $$\rm{Ir}_3M_2^{+/3+}$$ (C2v, 1A1) (M = Li, Na, K and Be, Ca) bimetallic clusters which also possess the corresponding d-orbital aromatic characters.

Theoretical investigations of the chemical bonding in MM'O2 clusters (M, M' = Be, Mg, Ca).

Motivated by the known stability of the somewhat unusual Be2O2 rhombus, which features a short Be-Be distance but no direct metal-metal bonding, we investigate the nature of the bonding interactions in the analogous clusters MM'O2 (M, M' = Be, Mg, Ca). CCSD/cc-pVTZ and CCSD(T)/cc-pVQZ calculations, amongst others, are used to determine optimized geometries and the dissociation energies for splitting the MM'O2 clusters into metal oxide monomers. The primary tools used to investigate the chemical bonding are the analysis of domain-averaged Fermi holes, including the generation of localized natural orbitals, and the calculation of appropriate two- and three-center bond indices. Insights emerging from these various analyses concur with earlier studies of M2O2 rhombic clusters in that direct metal-metal bonding was not observed in the MM'O2 rings whereas weak three-center (3c) bonding was detected in the MOM' moieties. In general terms, these mixed MM'O2 clusters exhibit features that are intermediate between those of M2O2 and M'2O2, and the differences between the M and M' atoms appear to have little impact on the overall degree of 3c MOM' bonding. Graphical abstract Bonding situation in MM'O2 clusters (M, M' = Be, Mg, Ca).

Vibrational spectra and electronic structure of 11-vertex boron-containing clusters: a comparative study of [B11H11]2–, [CB10H11]–, and C2B9H11

Vibrational spectroscopy studies of 11-vertex boron-containing clusters [B11H11]2–(1), [2-CB10H11]– (2), and 2,3-C2B9H11 (3) revealed two low-frequency large-amplitude modes in their spectra and, therefore, structural nonrigidity of these polyhedra in contrast to related 12-, 10-, and 6-vertex closo-clusters. The nonrigidity originates from specific features of the electron density distribution. According to calculations within the framework of the "Atoms in Molecule" (AIM) theory, these polyhedra are characterized by the lack of many bond paths localized on corresponding edges, in particular, between boron atoms with coordination numbers of 6 and 5 (6k and 5k). Consequently, these polyhedra are composed of not only trigonal faces, i.e., formally do not have the closo-structure that was traditionally ascribed to them based on formal count of (2n + 2) valence electrons. According to calculations of three-center delocalization indices, the absence of bond paths is not equivalent to the lack of interaction between corresponding atoms since this interaction occurs through open three-center bonds. The mechanism and reasons for signal averaging observed in 11B NMR spectra of compounds 1 and 2 in contrast to 3 are analyzed.

The intramolecular hydrogen bond as a unit of molecular electronics: Molecular switching controlled by overcrowded intramolecular three-centered hydrogen bond

The equilibrium geometry of the 2,5-bis-[2-(pyridin-2-yl)-vinyl]-1[Formula: see text]-pyrrole calculated at the MP2/6-311[Formula: see text]G([Formula: see text],[Formula: see text]) level of theory evidences the breaking of one of the components in the three-centered intramolecular hydrogen bond due to the steric strain. For this reason, the three-centered intramolecular hydrogen bonding turns out to be asymmetric interaction involving the major and minor components. However, the reversible switching between these components under an external impact is also possible. Two different stable states with unequal geometric and electronic structure are observed in the derivatives of the 2,5-bis-[2-(pyridin-2-yl)-vinyl]-1[Formula: see text]-pyrrole. These molecules represent novel molecular switches operating due to the pendulum-like transition between the nonequivalent two-centered components of the overcrowded three-centered intramolecular hydrogen bond. Implantation of hydrogen bond as a unit of the molecular scale device enhances potential of molecular electronics and could serve as a step towards the construction of artificial biological ensembles.

Site-selective As–P substitution and hydrogen bonding in the crystal structure of philipsburgite, Cu5Zn((As,P)O4)2(OH)6·H2O

Philipsburgite, Cu5Zn((As,P)O4)2(OH)6·H2O, from the Middle Pit, Gold Hill Mine, Tooele Co., Utah, USA, was studied by single-crystal X-ray diffraction and scanning electron microscopy. The empirical formula of the studied sample is (Cu4.69Zn1.23)(As0.86P0.18O4)2(OH)5.61·H2O, which agrees well with the previous reports on the mineral. Philipsburgite is monoclinic, P21/c, a = 12.385(6), b = 9.261(4), c = 10.770(5) A, β = 97.10(1)o, V = 1225.7(9) A3 (at 100 K), and Z = 4. The crystal structure was refined to R1 = 0.046 for 2563 unique observed reflections with |Fo| ≥ 4σF. The crystal structure of philipsburgite is isotypic to that of kipushite and can be considered as a complex three-dimensional framework consisting of two types of layers stacked parallel to the a-axis. The A-type layer is formed by the edge-sharing Jahn–Teller-distorted Cuφ6 octahedra [φ = O2−, (OH)−, H2O]. Two adjacent octahedral layers are linked via (As2O4) tetrahedra. The B-type layer is built by corner-sharing (ZnO4) and (As1O4) tetrahedra and is formed by the four- and eight-membered tetrahedral rings. The A:B ratio of the A and B layers is equal to 2:1. The hydrogen bonding network in philipsburgite is rather complex and consists of two- and three-center hydrogen bonds. The As1 site accommodates ca. 18% of P and is a preferable position for the P substitution in philipsburgite. The observed selectivity of the As1 site for P may indicate that, for the intermediate compositions with the P:As ratios close to 1:1, there is a fully ordered species with P prevalent at the As1 site and As prevalent at the As2 site. The intermediate composition would, therefore, be Cu5Zn(AsO4)(PO4)(OH)6·H2O and such a mineral can be considered as a separate species, according to the rules of the International Mineralogical Association (IMA). Philipsburgite should be considered as structurally complex with the Shannon information contents of 4.954 bits/atom and 614.320 bits/cell. The obvious reason for the structural complexity of the mineral is its modularity, i.e., the presence of two structurally distinct modules, the octahedral–tetrahedral (A) and tetrahedral (B) layers.

Force constant decomposition for penta-coordinated XH3 Cl2- (X = C, Si, Ge) structures.

Based on the energy decomposition analysis of an interacting system, we propose a method for force constant decomposition analysis with respect to the specific normal coordinate. Using the presented method, we examined the penta-coordinated XH3Cl2- system (X = C, Si, Ge), which possesses a three-center four-electron bond. The origin of the difference in the stability of the penta-coordinated D3h structures was clearly shown to be the effect of electron delocalization-polarization term. © 2018 Wiley Periodicals, Inc.

Quantitative assessment of intermolecular interactions by atomic force microscopy imaging using copper oxide tips.

Atomic force microscopy is an impressive tool with which to directly resolve the bonding structure of organic compounds1-5. The methodology usually involves chemical passivation of the probe-tip termination by attaching single molecules or atoms such as CO or Xe (refs 1,6-9). However, these probe particles are only weakly connected to the metallic apex, which results in considerable dynamic deflection. This probe particle deflection leads to pronounced image distortions, systematic overestimation of bond lengths, and in some cases even spurious bond-like contrast features, thus inhibiting reliable data interpretation8-12. Recently, an alternative approach to tip passivation has been used in which slightly indenting a tip into oxidized copper substrates and subsequent contrast analysis allows for the verification of an oxygen-terminated Cu tip13-15. Here we show that, due to the covalently bound configuration of the terminal oxygen atom, this copper oxide tip (CuOx tip) has a high structural stability, allowing not only a quantitative determination of individual bond lengths and access to bond order effects, but also reliable intermolecular bond characterization. In particular, by removing the previous limitations of flexible probe particles, we are able to provide conclusive experimental evidence for an unusual intermolecular N-Au-N three-centre bond. Furthermore, we demonstrate that CuOx tips allow the characterization of the strength and configuration of individual hydrogen bonds within a molecular assembly.

Квантовохимическое моделирование строения молекул иминодиуксусной кислоты и ее производных в водной среде

Проведены компьютерные вычисления атомного строения молекулы иминодиуксусной кислоты и ее гидратов в вакууме и водной среде. Показано, что учет диэлектрической проницаемости водной среды приводит к изменению длин ковалентных связей между атомами, валентных углов, эффективных зарядов и энергии связей. При этом топология химических связей изомера не изменяется. Присоединение одной молекулы воды приводит к смене позиции иона водорода, связанной с переносом его от иона кислорода к иону азота, что приводит к образованию цвиттер-структуры. Показано, присоединение молекулы воды к молекуле иминодиуксусной кислоты сопровождается возникновением трехцентровой ковалентной связи, что является физико-химическим механизмом термодинамической устойчивости цвиттер-структуры молекулы в водной среде.

Quasi-Atomic Bonding Analysis of Xe-Containing Compounds.

The origin of bonding in the rare-gas-containing molecules HXeCCH, HXeCCXeH, and HXeOXeH is explored using a quasi-atomic orbital (QUAO) analysis. The QUAOs provide qualitative and quantitative data about bonding through transformations of the density matrix. Bond orders, kinetic bond orders, and the extent of transfer of charge are analyzed. Localized molecular orbitals formed from the QUAOs provide additional insights about the relative polarity of bonds formed by xenon. The analysis suggests significant covalent bonding for Xe-Y (Y = C, O) as well as Xe-H, with both bonds using the same pσ-type orbital on Xe. These covalent interactions are established by substantial charge shifts from Xe to Y as well as to H. Accordingly, a covalent three-center four-electron bond links the atoms H-Xe-Y. On the basis of the analysis, electrostatic interactions do not play a significant role in the Xe-Y or Xe-H bonding.