Dimethylarsenazid (CH3)2AsN3, Dimethylwismutazid (CH3)2BiN3 und Dimethylthalliumzid (CH3)2TiN3

The reaction of (CH₃)₂AsJ and AgN₃ yields (CH₃)₂AsN₃; a colourless liquid (b. p. 136°C) which dissolves as a monomeric in benzene. (CH₃)₂BiN₃ is precipitated in form of colourless needles (dec. temp. 150°C) from an etherical solution of Bi(CH₃)₃ and HN₃. According to its vibrational and mass spectra the molecules are not associated although the (CH₃)₂BiN₃ is not soluble; dipole association of this polar molecules is assumed for the crystal structure. (CH₃)₂TlN₃ can be obtained from TI(CH₃)₃ and ClN₃ as well as from (CH₃)₂TlOH and HN₃ in form of colourless needles and leaves (dec. temp. 245°C). According to its vibrational spectra it has an ionic structure, (CH₃? Tl? CH₃)⁺N^?₃.     

Neue metallorganisch substituierte Indium–Stickstoff-Verbindungen. Synthese und Kristallstrukturen von [{Cp(CO)3Mo}2InN(SiMe3)2] und [{Cp(CO)3Mo}In{N(SiMe3)2}2]

New Organometallic Indium Nitrogen Compounds. Synthesis and Crystal Structures of [{Cp(CO)₃Mo}₂InN(SiMe₃)₂] and [{Cp(CO)₃Mo}In{N(SiMe₃)₂}₂] The reaction of [{Cp(CO)₃Mo}₂InCl] with LiN · (SiMe₃)₂ leads to the formation of [{Cp(CO)₃Mo}₂InN · (SiMe₃)₂] ( 1 ). 1 is monomeric and it contains an indium atom which is coordinated in a trigonal planar manner by two {Cp(CO)₃Mo} fragments and a N(SiMe₃)₂ group. The corresponding bis-amide [{Cp(CO)₃Mo}In{N(SiMe₃)₂}₂] ( 2 ) is prepared by the reaction of [{Cp(CO)₃Mo}InCl₂] with two equivalents of LiN(SiMe₃)₂. In analogy to 1, 2 is monomeric and it contains an indium atom in a trigonal planar coordination.     

Synthese,Eigenschaften und Struktur von cis-Dihydridoazido-tris(triphenylphosphino)-iridium

Synthesis, Properties, and Structure of cis-Dihydrido Azido Tris(triphenylphosphino) Iridium cis-IrH₂(N₃)(PPh₃)₃ is formed from IrCl₃(PPh₃)₃ and NaN₃ in alcohol. The solvent transfers the hydride ions whereby aldehyde is formed. The creme-colored cis-IrH₂(N₃)(PPh₃)₃ is a diamagnetic low-spin complex. Exposure to light yields H₂ and Ir(N₃)(PPh₃)₃ in a reversible process. The cis position of the hydrido ligands is confirmed by the i.r. and H-N.M.R. spectra. Cis-IrH₂(N₃)(PPh₃)₃ crystallizes in the monoclinic system with the space group P2₁/c. The crystal structure exhibits isolated octahedral complexes, in which one hydrido ligand is located trans to the azido group. The other one being trans to one of the phosphine ligands.     

Preparation of Z-scheme WO3(H2O)0.333/Ag3PO4 composites with enhanced photocatalytic activity and durability

Ag₃PO₄ is widely used in the field of photocatalysis because of its unique activity. However, photocorrosion limits its practical application. Therefore, it is very urgent to find a solution to improve the light corrosion resistance of Ag₃PO₄. Herein, the Z-scheme WO₃(H₂O)_0.333/Ag₃PO₄ composites are successfully prepared through microwave hydrothermal and simple stirring. The WO₃(H₂O)_0.333/Ag₃PO₄ composites are characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and UV-Vis spectroscopy. In the degradation of organic pollutants, WO₃(H₂O)_0.333/Ag₃PO₄ composites exhibit excellent performance under visible light. This is mainly attributed to the synergy of WO₃(H₂O)_0.333 and Ag₃PO₄. Especially, the photocatalytic activity of 15%WO₃(H₂O)_0.333/Ag₃PO₄ is the highest, and the methylene blue can be completely degraded in 4 min. In addition, the stability of the composites is also greatly enhanced. After five cycles of testing, the photocatalytic activity of 15%WO₃(H₂O)_0.333/Ag₃PO₄ is not obviously decreased. However, the degradation efficiency of Ag₃PO₄ was only 20.2%. This indicates that adding WO₃(H₂O)_0.333 can significantly improve the photoetching resistance of Ag₃PO₄. Finally, Z-scheme photocatalytic mechanism is investigated.     

Determination of the maximum monolayer dispersion and dispersed state for WO3 on γ-Al2O3

The maximum monolayer dispersion (the threshold) for WO₃ on γ-Al₂O₃ calcined at 500°, 550°, 600°, and 640°C has been determined quantitatively by XRD (amount of crystalline phase) and XPS (intensity ratios I_w4f/I_Al2). The results show that if the amount of WO₃ loaded is lower than the maximum monolayer dispersion, WO₃ will react with γ-Al₂O₃ to form surface compound due to mutual ionic interaction, and will be dispersed on γ-Al₂O₃ surface as monolayer then. In case the amount is higher than this value, the residual crystalline WO₃ will remain. The maximum monolayer dispersion (threshold) is 0.21 g and 0.20 g WO₃/100 m² γ-Al₃O₃ by XRD and XPS respectively. It agrees with the value (0.189 g WO₃/100 m² or 4.90 × 10^?18 W atoms/m²) calculated from the model on assumption that the WO₃ is dispersed as a closed-packed monolayer on γ-Al₂O₃ surface. Inasmuch as WO₃/γ-Al₂O₃ system is stable up to higher temperature, e.g. 700°C, than MoO₃/γ-Al₂O₃ system, WO₃ seems unfavorable to form new bulk compound with γ-Al₂O₃ at that temperature. However, Al₂(MoO₄)₃ forms perceptibly in MoO₃/γ-Al₂O₃ system at 500°C. Besides, the size of residual crystalline WO₃ in WO₃/γ-Al₂O₃ is much smaller than that of MoO₃ in MoO₃/γ-Al₂O₃. It might be the reason that WO₃/γ-Al₂O₃ catalyst is superior to MoO₃/γ-Al₂O₃ in hydrodesulfurization (HDS) or hydrodenitrogenation (HDN) in some cases.     

Formation and transformation of Amminecarbonatocobalt(III) Complexes

The preparation is described of [CoCO₃(NH₃)₅]ClO₄ · H₂O, trans-[CoCO₃(NH₃)₄(¹⁵NH₃)]ClO₄, and trans-[CoCO₃(NH₃)₄(NH₂CH₃)]ClO₄. The transformation reactions of these complexes, in which a chelate carbonate ligand is formed and one NH₃ is eliminated, were studied in solution and in the solid state. ¹H NMR spectroscopy is used for the identification of the products. It is shown that the transformation reactions are not stereospecific.     

Theoretical study on the reaction mechanism of (CH<Subscript>3</Subscript>)<Subscript>3</Subscript>CO<Superscript>.</Superscript> radical with NO

The reaction mechanism of (CH₃)₃CO^. radical with NO is theoretically investigated at the B3LYP/6-31G* level. The results show that the reaction is multi-channel in the single state and triplet state. The potential energy surfaces of reaction paths in the single state are lower than that in the triple state. The balance reaction: (CH₃)₃CONO⇔(CH₃)₃CO^.+NO, whose potential energy surface is the lowest in all the reaction paths, makes the probability of measuring (CH₃)₃CO^. radical increase. So NO may be considered as a stabilizing reagent for the (CH₃)₃CO^. radical.     

The Role of Oxygen in the Degradation of Methylammonium Lead Trihalide Perovskite Photoactive Layers

In this paper we report on the influence of light and oxygen on the stability of CH₃NH₃PbI₃ perovskite‐based photoactive layers. When exposed to both light and dry air the mp‐Al₂O₃/CH₃NH₃PbI₃ photoactive layers rapidly decompose yielding methylamine, PbI₂, and I₂ as products. We show that this degradation is initiated by the reaction of superoxide (O₂^?) with the methylammonium moiety of the perovskite absorber. Fluorescent molecular probe studies indicate that the O₂^? species is generated by the reaction of photoexcited electrons in the perovskite and molecular oxygen. We show that the yield of O₂^? generation is significantly reduced when the mp‐Al₂O₃ film is replaced with an mp‐TiO₂ electron extraction and transport layer. The present findings suggest that replacing the methylammonium component in CH₃NH₃PbI₃ to a species without acid protons could improve tolerance to oxygen and enhance stability.     

Synthesis and Structure of Cyclic Selenium Oxide SeVISe2IVO7

Nitromethane is the only presently known organic solvent for highly reactive selenium trioxide (SeO₃)₄. The stability of the solutions is limited and the beginning of the reaction between both components depends significantly on concentration and temperature. The nitromethane solvate of cyclic triselenium heptoxide Se₃O₇ · CH₃NO₂ is the major solid product at the temperature 20–30°C and concentration range 3–20% SeO₃. Crystal and molecular structure of this compound was determined by X-ray structure analysis and vibrational spectroscopy. The solvating molecule CH₃NO₂ is removable from Se₃O₇ · CH₃NO₂ in vacuo. If reaction temperature does not exceed 10°C, selenium pentoxide (Se₂O₅)_n is formed instead of Se₃O₇ · CH₃NO₂. Dinitrosyl triselenate (NO)₂Se₃O₁₀, nitrosyl hydrogendiselenate NOHSe₂O₇, nitrosyl hydrogenselenate NOHSeO₄, nitrosyl hydrogenselenatoselenite NOHSe₂O₆ and selenium dioxide (SeO₂)_n were further identified in the solid reaction products. The selenic and/or oligoselenic acids remains in the nitromethane solution. CO₂ and N₂O₃ were found as gaseous products.     

Azido-Derivate des Pentamethylcyclopentadienyl-Vanadium(IV)-Fragments. Molekülstrukturen der Zweikernkomplexe [Cp*VCl(N3)(μ-N3)]2 und [Cp*V(N3)2(μ-N3)]2

Azido Derivatives of the Pentamethylcyclopentadienyl Vanadium(IV)-Fragment. Molecular Structures of the Binuclear Complexes [Cp*VCl(N₃)(μ-N₃)]₂ and [Cp*V(N₃)₂(μ-N₃)]₂ The stepwise reaction of Cp*VCl₃ with excess trimethylsilyl azide (Me₃Si–N₃) in solution leads to the paramagnetic, azido-bridged complexes [Cp*VCl₂(μ-N₃)]₂ ( 3 ), [Cp*VCl(N₃)(μ-N₃)]₂ ( 4 ) and [Cp*V(N₃)₂(μ-N₃)]₂ ( 5 ) which were characterized by their IR and mass spectra. The azide-rich binuclear complex 5 is also formed if a pentane solution of Cp*V(CO)₄ is stirred in the presence of excess Me₃Si–N₃ in an open vessel. According to the X-ray structure analyses both 4 and 5 are centrosymmetric molecules with a planar V(N)₂V four-membered ring. In the absence of free trimethylsilyl azide, solutions of 3 – 5 lose dinitrogen slowly; in the presence of traces of air, 5 is thereby converted to the diamagnetic, oxo-bridged complex [Cp*V(O)(N₃)]₂(μ-O) ( 6 ).     

Quantum-Chemical Investigation of Structure and Vibration Spectrum of [C(NPCl<Subscript>3</Subscript>)<Subscript>3</Subscript>]<Superscript>+</Superscript> Cation

Structural parameters of the cation [C(NPCl₃)₃]⁺ in vacuum and in acetonitrile are calculated by the methods RHF/6-311G(3d₆), RHF/6-31(3d₅) and B3LYP/6-311(3d₅f₇). Formation energy of the free adduct (MeCN) 2[C(NPCl₃)₃]⁺ is calculated and nonspecific character of interaction of the cation with liquid acetonitrile is established. Vibration spectrum of the cation is calculated and theoretical interpretation of IR and Raman spectra of the salt [C(NPCl₃)₃]⁺[SbCl₆]^? is refined.     

Alkyl complexes of cobalt in catalytic cycles for hydrogenation of alkenes

The potential of several alkylcobalt complexes as catalysts for hydrogenation and isomerization of alkenes has been investigated. The complexes CH₃Co(CO)₂(Pom-Pom) (Pom-Pom = 1,2 bis(dimethoxyphosphino)ethane), CH₃Co(CO)₃P(OMe)₃ and C₆H₅CH₂Co(CO)₃PPh ₃ are compared to CH₃Co(CO)₂(P(OMe)₃)₂, for their ability to function in catalytic cycles. Each is active for hydrogenation and isomerization of alkenes under conditions where the carbonylation-decarbonylation equilibrium is readily established. The lifetime for the complexes is much shorter than for CH₃Co(CO)₂ (P(OMe)₃)₂ suggesting that two phosphorus donors in trans positions in an intermediate is a requirement for catalyst stability in these alkylcobalt complexes.     

Phosphaniminato-Komplexe von Titan(IV). Die Kristallstrukturen von [TiCl3(NPEt3)]2, [TiCl3(NPEt3)(THF)2] und [TiCl4{Me2Si(NPEt3)2}]

Phosphoraneiminato Complexes of Titanium(IV). Crystal Structures of [TiCl₃(NPEt₃)]₂, [TiCl₃(NPEt₃)(THF)₂], and [TiCl₄{Me₂Si(NPEt₃)₂}] [TiCl₃(NPEt₃)]₂ ( 1 ) is formed from titanium(IV) chloride and the silylated phosphaneimine Me₃SiNPEt₃ in dichloromethane as reddish-brown, moisture-sensitive crystals. According to the crystal structure analysis these crystals show centrosymmetric Ti₂N₂ four-membered rings with Ti–N distances of 184.7 and 210.3 pm. With tetrahydrofurane 1 forms yellow, moisture sensitive crystals of the solvate [TiCl₃(NPEt₃)(THF)₂] ( 2 ), in which the titanium atom is octahedrally coordinated. The THF molecule which is in trans position to the phosporaneiminato ligand realizes but a very weak Ti–O bond of 238.0 pm, the cis THF molecule shows a Ti–O distance of 213.7 pm. With 173.4 pm along with a TiNP bond angle of 160.0° the TiN distance is very short. The bis(phosphaneimine) complex [TiCl₄{Me₂Si(NPEt₃)₂}] ( 3 ) is formed as colourless crystals in low yield in the reaction of titanium(IV) chloride with Me₃SiNPEt₃ and trimethylcyclopentadienylsilane. In 3 the titanium atom is surrounded by four chlorine atoms in a distorted octahedral fashion and by the two N atoms of the Me₂Si(NPEt₃)₂ molecule with TiN distances of 205.6 pm.     

Theoretical Studies of Inorganic Compounds. 19 1) Quantum Chemical Investigations of the Phosphane Complexes X3B‐PY3 and X3Al‐PY3 (X = H,F, Cl; Y = F,Cl, Me,CN)

We report about quantum chemical ab initio calculations at the MP2/6‐311+G(2d)//MP2/6‐31G(d) level and DFT calculations at BP86/TZP of the geometries and bond dissociation energies of the borane‐phosphane complexes X₃B‐PY₃ and the alane‐phosphane complexes X₃Al‐PY₃ (X = H, F, Cl; Y = F, Cl, Me, CN). The nature of the B‐P and Al‐P bonds is analyzed with a bond energy partitioning method. The calculated bond dissociation energies D_e of the borane adducts X₃B‐PY₃ show for the phosphane ligands the trend PMe₃ > PCl₃ ∼ PF₃ > P(CN)₃. A similar trend PMe₃ > PCl₃ > PF₃ > P(CN)₃ is predicted for the alane complexes X₃Al‐PY₃. The order of the Lewis acid strength of the boranes depends on the phosphane Lewis base. The boranes show with PMe₃ and PCl₃ the trend BH₃ > BCl₃ > BF₃ but with PF₃ and P(CN)₃ the order is BH₃ > BF₃ > BCl₃. The bond energies of the alane complexes show always the trend AlCl₃ ≥ AlF₃ > AlH₃. The bonding analysis shows that it is generally not possible to correlate the trend of the bond energies with one single factor which determines the bond strength. The preparation energy which is necessary to deform the Lewis acid and Lewis base from the equilibrium form to the geometry in the complex may have a strong influence on the bond energies. The intrinsic interaction energies may have a different order than the bond dissociation energies. The trend of the interaction energies are sometimes determined by a single factor (Pauli repulsion, electrostatic attraction or covalent bonding) but sometimes all components are important. The higher Lewis acid strength of BCl₃ compared with BF₃ in strongly bonded complexes is not caused by the deformation energy of the fragments but it is rather caused by the intrinsic interaction energy. P(CN)₃ is a weaker Lewis base than PF₃, PCl₃ and PMe₃ mainly because of its weaker electrostatic attraction. The complex H₃B‐P(CN)₃ is predicted to have a bond dissociation energy D_o = 14.8 kcal/mol which should be sufficient to synthesize the compound as the first adduct with the ligand P(CN)₃. The calculated bond energies at the BP86 level are in most cases very similar to the MP2 results. In a few cases significantly different absolute values have been found which are caused by the method and not by the quality of the basis set.     

F3SiSH and (F3Si)2S: Conflicting Observations Resolved by Unambiguous Syntheses

The reaction between liquid F₃SiI and red HgS mainly yields the disilylsulfane (F₃Si)₂S and, in smaller amounts, hitherto unknown (F₃SiS)₂SiF₂. These fluorosilylsulfanes have different thermal stabilities. (F₃Si)₂S is a versatile precursor for F₃Si derivatives, and at ambient temperature it is stable, while (F₃SiS)₂SiF₂ decomposes rapidly. F₃SiSH has been obtained, along with F₃SiBr, by selective cleavage of one of the Si–S bonds in (F₃Si)₂S with HBr in the liquid phase and was for the first time unambiguously characterized. Contrary to previous reports, (F₃Si)₂O rather than (F₂SiS)₂ is formed when SiF₄ is passed over SiS₂ at 1298 K in a quartz tube. Raman and infrared spectra of (F₃Si)₂S, F₃SiSH and its deuterated derivative F₃SiSD have been measured and assigned to vibrational fundamentals. Multinuclear NMR spectra have been recorded.     

Studies on the thermal decomposition of calcium carbonate in the presence of alkali salts (Na2Co3, K2CO3 and NaCl)

Mixtures of CaCO₃ and varying amounts of Na₂CO₃, K₂CO₃ and NaCl were subjected separately to thermal analysis. DTG, DTA, TG analyses indicate that the presence of alkali salts in CaCO₃ influences its decomposition behaviour. A minimum DTA peak temperature of CaCO₃ decomposition is noticed at low concentrations of alkali salts (K₂CO₃ and Na₂CO₃); an increase in concentration increases the DTA peak temperature. However, in the case of NaCl no appreciable lowering of the DTA peak temperature of CaCO₃ decomposition is observed. Similarly, the minimum temperature at which decomposition completes is found to correspond to the concentration of 1 per cent salt (K₂CO₃ and Na₂CO₃) in CaCO₃.     

Übergangsmetall-Silyl-Komplexe, 44. Darstellung der zweikernigen Silyl-Komplexe (CO)3(R3Si)Fe(μ-PR′R′′)Pt(PPh3)2 durch oxidative Addition von (CO)3(R′R′′HP)Fe(H)SiR3 an (C2H4)Pt(PPh3)2

Transition Metal Silyl Complexes, 44. — Preparation of the Binuclear Silyl Complexes (CO)₃(R₃Si)Fe(μ-PR′R′′)Pt(PPh₃)₂ by Oxidative Addition of (CO)₃(R′R′′HP)Fe(H)SiR₃ to (C₂H₄)Pt(PPh₃)₂ The complexes (CO)₃(R′R′′HP)Fe(H)SiR₃ ( 1 ) [PHR′R′′ = PHPh₂, PH₂Ph, PH₂Cy; SiR₃ = SiPh₃, SiPh₂Me, SiPhMe₂, Si(OMe)₃] react with Pt(C₂H₄)(PPh₃)₂ to give the dinuclear, silyl-substituted complexes (CO)₃(R₃Si)Fe(μ-PR′R′′)Pt(PPh₃)₂ ( 2 ) in high yields. Upon reaction of 2 (R = R′ R′′ = Ph) with CO, the PPh₃ ligand at Pt being trans to the PPh₂ bridge is exchanged, and (CO)₃(Ph₃Si)Fe(μ-PPh₂)Pt(PPh₃)CO ( 3 ) is formed. Complex 3 is characterized by an X-ray structure analysis. The rather short Fe — Si distance [233.9(2) pm] and the infrared spectrum of 3 indicate that the Fe — Pt bond is quite polar.     

Chemical effects of heavy metals on the hydration of calcium sulphoaluminate 4CaO·3Al2O3·SO3

The system 4CaO·3Al₂O₃·SO₃-CaSO₄·2H₂O-Ca(OH)₂ was hydrated in the presence of ten dopants, specifically soluble salts of heavy metals.When added in 10% amount, the effect of each salt is strongly evident at shorter curing times, the hydration kinetics being more favoured in the order Pb(NO₃)₂2CrO₄< Cd(NO₃)₂< Zn(NO₃)₂t~Mn(NO₃)₃=K₂MoO₄3)₂3)₂3)₃3)₃. At longer curing times the differences among the systems decrease significantly.The 28-day compressive strength is almost the same for all the systems except those containing Pb(NO₃)₂, K₂MoO₄ and K₂CrO₄.     

Theoretical Studies of Inorganic Compounds. 361) Structures and Bonding Analyses of Beryllium Chloro Complexes with Nitrogen Donors

Quantum chemical calculations at various levels of theory (BP86, B3LYP, MP2, CCSD(T), CBS‐QB3) of the beryllium complexes [BeCl₂(NHPH₃)], [BeCl₂(NHPH₃)₂], [BeCl₃(py)]^?, [BeCl₂(NH₃)], [BeCl₂(NH₃)₂], [BeCl₃(py)]^? and [BeCl₃(NH₃)]^? as well as the boron compounds [BCl₃(py)] and [BCl₃(NH₃)] show that BeCl₂ is a very strong Lewis acid. The theoretically predicted bond dissociation energy at CBS‐QB3 of Cl₂Be‐NH₃ (D_e = 32.5 kcal/mol)is even higher than that of Cl₃B‐NH₃ (D_e = 28.6 kcal/mol). Even the second ammonia molecule in [BeCl₂(NH₃)₂] still has a strong bond with D_e = 24.2 kcal/mol. The theoretically predicted bond strengths for the phosphaneimine ligands in [BeCl₂(NHPH₃)₂] are D_e = 46.7 kcal/mol for the first ligand and D_e = 29.8 kcal/mol for the second. The anion BeCl₃^? is a moderately strong Lewis acid which has bond energies of D_e = 14.1 kcal/mol in [BeCl₃(py)]^? and D_e = 14.2 kcal/mol in [BeCl₃(NH₃)]^?. The higher bond energy of [BeCl₂(NH₃)] compared with [BCl₃(NH₃)] comes from less deformation energy for BeCl₂ than for BCl₃. The intrinsic attraction between BeCl₂ and NH₃ calculated with frozen geometries of the complex geometry is ～5 kcal/mol less than the attraction between BCl₃ and NH₃. The bonding analysis with the EDA method shows that the attractive energy of the beryllium complexes comes manly from electrostatic attraction. The larger contribution of the electrostatic term is the most significant difference between the nature of the donor‐acceptor bonds of the beryllium and boron complexes.     

Spectra and structure of gallium compounds: Part X. Infrared and Raman spectra,vibrational assignment,and normal coordinate calculations for trimethylaminegallium trichloride

The far IR (450–480 cm^?1) and Raman (3200–3230 cm^?1) spectra of (CH₃)₃ NGaCl₃ have been recorded in the solid state and interpreted in detail on the basis of C₃ molecular symmetry. A modified valence force field model is used to calculate the frequencies and potential energy distribution of the adduct. The calculated force constants of the adduct are compared with those previously reported for the free Lewis acid and the free Lewis base moieties, and the observed differences ascribed to geometrical changes of the uncomplexed species on adduct formation and explained on the basis of the VSEPR model and non-bond interactions. Extensive coupling is observed between the GaN stretching mode and the NC₃ symmetric stretching and the NC₃ symmetric deformational modes. Strong coupling interaction is also found between the GaCl₃ antisymmetric stretch and the NC₃ antisymmetric deformation. The calculated value of 2.50 mdyn Å^?1 for the GaN stretching force constant in (CH₃)₃NGaCl₃ is larger than any of those previously determined in complexes such as (CH₃)₃NGaH₃ (2.43 mdyn Å^?1), (CH₃)₃NGa(CH₃)₃ (1.61 mdyn Å^?1), and H₃NGa(CH₃)₃ (1.08 mdyn Å^?1). The observed variations in the magnitudes of the stretching force constants of the donor—acceptor dative bond is found to be consistent with the estimated relative stabilities of this series of adducts.