Electron diffraction study of the molecular structure ofo-chloroanisole using a dynamic nonparametrized model

The geometrical parameters of the o-chloroanisole molecule were determined by gas phase electron diffraction in terms of the dynamic model using vibrational spectroscopy data and quantum chemical calculations. A new approach based on Tikhonov's regularization method is used to explicitly define the internal rotation potential of the methoxy group. It was found that the nonparametric internal rotation potential has two minima, one of which corresponds to the planar (?=0°) and another to orthogonal (?=90°) orientation of the O?CH₃ bond relative to the plane of the benzene ring. The difference between the energies of the orthogonal and planar conformers is 0.9–1.0 kcal/mole, and the height of rotation barriers at ??65° is 1.4–1.6 kcal/mole, which confirms the results of quantum chemical calculations, indicating that the orthogonal conformer is present in substantial amounts (～30%). The following basic geometrical parameters were found (r_a in Å, ∠_α in deg, the error equals 3σ): r(C?C)_ave=1.398(4); r(O?C_Ph)=1.358(36); r(O?C_Me)=1.426(21);r(C?Cl)=1.733(4);r(C?H)_Ph=1.086(6);r(C?H)_Me=1.095(6); ∠CC_OC_Cl=118.7(2.2); ∠C_OCC=119.9(2.5); ∠C_OC_ClC=121.5(1.1); ∠COC=117.6(2.6); ∠C_OCCl=119.1(2.1); ∠CCO=124.7(1.2). The results are compared with the data for related compounds. Stereochemical features of o-anisoles that are responsible for the orthogonal conformer are discussed.     

Molecular structure of 1,2,4-triazole

The molecular structure of 1,2,4-triazole has been determined by gas phase electron diffraction. The intemuclear distances and bond angles were obtained by applying a least-squares analysis to the experimental intensity. The bond distances (r_g) and bond angles were N₁-N₂ = 1.380 ± 0.010 Å, N₂C₃ = 1.329 ± 0.009 Å, C₃-N₄ = 1.348 ± 0.009 Å, N₁-C₅ = 1.377 ± 0.004 Å, N₄C₅ = 1.305 Å (calculated value). N-H = 0.990 Å, C-H = 1.054 Å, ∠N₁N₂C₃ = 102.7± 0.5°, ∠N₂C₃N₄ = 113.8 ± 1.3°, ∠N₂N₁C₅ = 108.9 ± 0.8°, ∠H₁N₁N₂ = 110.9°, ∠H₂C₃N₄ = 119.2°, ∠H₃C₅N₁ = 131.0°, ∠C₃N₄C₅ = 105.7° (calculated value) and ∠N₄C₅N₁ = 108.7° (calculated value).     

Internal Rotation and Equilibrium Structure of the Bromonitromethane Molecule According to Gas Electron Diffraction Data and Quantum Chemical Calculations

The structure and internal rotation of the bromonitromethane molecule are studied using electron diffraction analysis and quantum chemical calculations. The electron diffraction data are analyzed within the models of a general intramolecular anharmonic force field and quantum chemical pseudoconformers to account for the adiabatic separation of a large amplitude motion associated with the internal rotation of the NO₂ group. The following experimental bond lengths and valence angles are obtained for the equilibrium orthogonal configuration of the molecule with C_s symmetry: r_e(N=O) = 1.217(5) Å, r_e(C–N) = 1.48(2) Å, r_e(C–Br) = 1.919(5) Å, ∠_еBr–C–N = 109.6(9)°, ∠_еO=N=O = 125.9(9)°. The equilibrium geometry parameters are in good agreement with CCSD(T)/cc-pVTZ calculations. Thermally averaged parameters are calculated using the equilibrium geometry and quadratic and cubic quantum chemical force constants. The barrier to internal rotation cannot be determined reliably based on the electron diffraction data used in this work. There is a 82% probability that the equilibrium configuration with orthogonal C–Br and N=O bonds is most preferable, and internal rotation barrier does not exceed 280 cm^-1, which agrees with CCSD(T)/cc-pVTZ calculations.     

Ab initio molecular fragment calculations with pseudopotentials: Model peptide studies

The energetics of rotation about the N? C′(ω); N? C^α(φ), and C^α? C′(?) bonds of the peptide unit have been investigated in the pseudo-FSGO fragment scheme on model compounds formamide and N-methylacetamide. The results indicated that the position of the minimum in ω is in the near vicinity of 0°, i.e., the planar arrangement of the peptide unit. The minimum in φ (C′? N? C^α? H) has been found to be 180° and in ψ(H? C^α? C′? N) to be 60°, in good agreement with PCILO and Gaussian-70 results.     

Internal rotation and equilibrium structure of the 2-methyl-2-nitropropane molecule from joint processing of gas phase electron diffraction data,vibrational and microwave spectroscopy data,and quantum chemical calculation results

The structure and internal rotation of the 2-methyl-2-nitropropane molecule is studied by electron diffraction and quantum chemical calculations with the use of microwave and vibrational spectroscopy data. The electron diffraction data are analyzed within the general intramolecular anharmonic force field model and the quantum chemical pseudoconformer model, considering the adiabatic separation of the degree of freedom of large amplitude motion, i.e., the internal rotation of the NO₂ group. The equilibrium eclipsed configuration of the C _s symmetry molecule has the following experimental bond lengths and valence angles: r _e(N=O) = 1.226//1.226(8) Å, r _e(C–N)//r _e(C–C) = 1.520//1.515/1,521(4) Å, ∠_еC–C–N = = 109.1/106,1(8)°, ∠_еO=N=O = 124.2(6)°, ∠_eC–C–H_avg = 110(3)°. The equilibrium geometry parameters are well consistent with MP2/cc-pVTZ quantum chemical calculations and microwave spectroscopy data. The thermally average parameters previously obtained within the small vibration model show a satisfactory agreement with the new results. The electron diffraction data used in this work do not allow a reliable determination of the barrier to internal rotation. However, at a barrier of 203(2) cal/mol, which is derived from the microwave study, it follows from the electron diffraction data that the equilibrium configuration must correspond to an eclipsed arrangement of C–C and N=O bonds, which is also consistent with the results of quantum chemical calculations of various levels.     

The molecular structure of gaseous tetrafluoro-p-benzoquinone and tetramethyl-p-benzoquinone as determined by electron diffraction

The molecular structures of gaseous tetrafluoro-p-benzoquinone (p-fluoranil) and tetramethyl-p-benzoquinone (duroquinone) have been investigated by electron diffraction. Except for the methyl group hydrogen atoms, the molecules are planar to within experimental error, but small deviations from planarity are completely compatible with the data. Values for the geometrical parameters (r_adistances and r_α with parenthesized uncertainties of 2σ including estimated uncertainty in the electron wavelength and correlation effects, are as follows. Tetrafluoro-p-benzoquinone: D_2h symmetry (assumed); r(C0) = 1.211(6) Å, r(CC) = 1.339(12) Å, r(C-C) = 1.489(5') Å, r(C-F) = 1.323(5) Å, ∠C-C-C = 116.8(7)° and ∠C-C-F = 116.1(7)°. Tetramethyl-p-benzoquinone: C_2h symmetry (assumed);r(C-H) = 1.102(18) Å, r(CO) = 1.229(8) Å, r(CC) = 1.352(8) Å, r(C_sp2-C_sp2) = 1.491(11) Å, r(C_sp2-C_sp3) = 1.504(12) A, ∠C-CO-C = 120.8(8)°. ∠C-C-CH₃ = 116.1(8)°, ∠C-C-H = 110.5(34)° and α₁ = α₂ (methyl torsion = 30° (assumed).     

The molecular structure of gaseous tetrachloro-p-benzoquinone and tetrachloro-o-benzoquinone by electron diffraction

The structures of tetrachloro-p-benzoquinone and tetrachloro-o-benzoquinone (p- and o-chloranil) have been investigated by gas electron diffraction. The ring distances are slightly larger and the carbonyl bonds slightly smaller than in the corresponding unsubstituted quinones. The molecules are planar to within experimental error, but small deviations from planarity such as those found for the para compound in the crystal are completely compatible with the data. Values for the geometrical parameters (r_a distances and bond angles) and for some of the more important amplitudes (l) with parenthesized uncertainties of 2σ including estimated systematic error and correlation effects are as follows. Tetrachloro-p-benzoquinone: D_2h symmetry (assumed); r(CO) = 1.216 Å(4), r(CC) = 1.353 Å(6), r(C-C) = 1.492 Å(3), r(C-Cl) = 1.701 Å(3), ∠C-C-C = 117.1° (7), ∠CC-C1 = 122.7° (2), l(CO)= 0.037 Å(5), l(CC) = l(C-C) - 0.008 Å(assumed) = 0.049 Å(7), and l(C-Cl) = 0.054 Å(3). Tetrachloro-o-benzoquinone: C_2v symmetry (assumed); r(CO) = 1.205 Å(5), r(CC) = 1.354 Å(9), r(C_cl-C_cl) = 1.478 Å(28), r(Co-C_cl) = 1.483 Å(24), r(C_o-C_o) = 1.526 Å(2), r(C-Cl)= 1.705 Å(3), <C_o-CO = 121.0° (22), ∠C-C-C = 117.2° (9), ∠C_co, ClC-Cl = 118.9° (22), ∠C_ccl, ClC-Cl = 122.2°(12), l(CO) = 0.039 Å(5), and l(C_cl-C_cl) = l(C_o-C_cl) = l( Co-Co) = l(CC) + 0.060 Å(equalities assumed) = 0.055 Å(9). Vibrational'shortenings (shrinkages) of a few of the long non-bond distances have also been measured.     

Ab initio studies on polymers. VII. Polyoxymethylene

The structure of an isolated, infinite polyoxymethylene chain has been investigated with the aid of the ab initio crystal orbital method applying a basis set of double-zeta quality. Restricting the primitive unit cell to a single CH₂O group, conformational potential curves as a function of the torsional angle have been evaluated. Only a single minimum closely corresponding to an all-gauche structure was detected. The all-trans conformation is a maximum on the energy curve for simultaneous rotation around C? O single bonds. Detailed geometry optimization in the vicinity of the all-gauche conformation led to the following structure: r_CO = r_OC = 1.425 Å, r_CH = 1.072 Å, ∠HCH = 111.7°, ∠OCO = 110.9°, ∠COC = 115.1°, and τ_OCOC = 70.75°. The computed torsional angle τ_OCOC lies midway between the hexagonal (78.2°) and the orthorhombic (63.5°) modification of solid polyoxymethylene.     

Molecular structure and conformational composition of gaseous 1,1-dichloro-2-bromomethyl-cyclopropane and 1,1-dichloro-2-cyanomethyl-cyclopropane as determined by electron diffraction

The molecular structure of the title compounds have been investigated by gas-phase electron diffraction. Both molecules exist as about equal amounts of the two gauche conformers. There is no evidence for the presence of a syn conformer, but small amounts of this form cannot be excluded. Some of the important distance (r_a) and angle (∠_α) parameters for 1,1-dichloro-2-bromomethyl-cyclopropane are: r(CH) = 1.095(19) Å, r(C₁C₂) = 1.476(11) Å, r(C₂C₃) = 1.517(31) Å, r(CCH₂Br) = 1.543(32) Å, r(CCl) = 1.752(6) Å, r(CBr) = 1.950(13) Å, ∠CCBr = 110.5(1.9)°, ∠ClCCl = 111.9(6)°, ∠CCC = 117.5(1.3)°, σ₁ (CC torsion angle between CBr and the three-membered ring for gauche-1) = 116.2(5.6)°, σ₂ = −132.7(7.6). For 1,1-dichloro-2-cyanomethyl-cyclopropane the parameter values are: r(CH) = 1.101(16) Å, r(C₁C₂) = 1.498(9) Å, r(C₂C₃) = 1.544(21) Å, r(C₂C₄) = 1.497(33) Å, r(CCN) = 1.466(26) Å, r(CN) = 1.165(8) Å, r(CCl) = 1.754(5) Å, ∠CCCN = 113.7(2.0)°, ∠CCC = 122.8(1.6)°, ClCCl = 112.5(4)°, σ₁ = 113(13)°, σ₂ = −124(10)°.     

Gas electron diffraction study of the molecular structure of NbCl4

The structure of the NbCl₄ molecule is studied experimentally by the synchronous electron diffraction and mass spectrometry methods. The model molecular geometries of C_2v, C_3v, D_2d, and T_d symmetries are verified. The advantages of the tetrahedral model over the other models are established. The thermally averaged parameters of the effective configuration of the NbCl₄ molecule are as follows: r_g(Nb?Cl)=2.279(5) Å, l(Nb?Cl)=0.073(2) Å, r_g(Cl?Cl)=3.692(17) Å, l(Cl?Cl)=0.275(11) Å, ∠_g(Cl-Nb-Cl)=108.2(5)°, and δ(Cl?Cl)=0.030(19) Å.     

Gas phase structures of the isomers of benzene,V. (dewar-benzene) by electron diffraction

The parent hydrocarbon, Dewar-benzene, has been studied by gas phase electron diffraction analysis. Assignment of C_2v symmetry gave excellent agreement between the experimental and theoretical data. The structural parameters obtained were in good agreement with previous electron diffraction structures of substituted derivatives of the Dewar-benzene series. The structural parameters with error limits are (cf. Fig. 2): r(C₃-C₆) = 1.574 ± 0.005 Å r(C₂-C₃) = 1.524 ± 0.002 Å, r(C₁-C₂) = 1.345 ± 0.001 Å, r(C₃-C₉) = 1.134 ± 0.004 Å, r(C₁-C₇) = 1.124 ± 0.004 Å, ∠C₁C₆C₅ = 116.7 ± 0.6°, ∠C₃C₆C₁ = 85.7 ± 0.2°, ∠C₆C₃C₉ = 108.0 ± 3.0°, ∠C₃C₂C₈ = 126.7 ± 2.5°, and α = 117.25 ± 0.6°. The angle γ was assumed to be 0°.     

The Iminoborane tBuB≡NtBu as a Dipolarphile in (2+3) Cycloadditions

The iminoborane tBuB≡NtBu and the diazomethane tBuCH=N₂ give the (2+3) cycloadduct [—HC(tBu)—N=N—N(tBu)=B(tBu)—] in a 1:1 reaction and the seven‐membered ring [—C(tBu)=N—NH—N(tBu)=B(tBu)—N(tBu)=B(tBu)—] in a 2:1 reaction. The (2+3) cycloadduct decomposes above 0 °C to give the seven‐membered ring, N₂, and HC(tBu)=N—N=CH(tBu) in the ratio 2:1:1. The borane tBuB≡NtBu and organic azides R″N₃ yield the (2+3) cycloadducts [—R″N—N=N—N(tBu)=B(tBu)—] (R″ = Me, Et, Pr, Bu, iBu, sBu, C₅H₁₁, c‐C₅H₉, c‐C₆H₁₁, Bzl, EtOOC).     

Studies of alkylmetal alkoxides of aluminium,gallium and indium : IV. The molecular structure of dimethylaluminium t-butoxide dimer by gas phase electron diffraction

The electron diffraction data for gaseous dimethylaluminium t-butoxide dimer are consistent with a molecular model of effective D_2h symmetry. The Al₂O₂ ring is planar and the three valencies of the O atoms are lying in a plane. The t-butyl groups undergo nonhindered or slightly hindered internal rotation. The most important bond distances and valence angles are: AlO = 1.864(6), AlC = 1.962(15), OC = 1.419(12), CC = 1.533(5) Å, ∠AlOAl = 98.1(0.7), ∠CAlC = 121.7(1.7) and ∠OCC = 110.4(0.5)°.     

Molecular structural of the gauche and trans conformers of ethylamine as studies by gas electron diffraction

The geometrical parameters for the two conformers, gauche (g) and trans (t), of ethylamine have been determined by a joint analysis of the electron diffraction intensity measured in the present study and the rotational constants reported in the literature. The optimized geometries estimated by an SCF MO calculation with a 4-31G(N*) basis set were also used in the analysis to complement the experimental data. The bond lengths (r_g) and the bond angels (r_z) determined are r(CH)_av = 1.107(6) Å r(CN)_t = 1. 470(10)Å, r(CN)_g = 1.475(10) Å r(CC)_t = 1.531(6) Å r (CC)_g = 1.524(6) Å , ∠CCN)_t = 115.0(3)°, and ∠CCCN_g = 109.7(3)°. The uncertainties represent estimated limits of error. The difference between the CCN_g and CCN_g angles predicted by a previous ab initio calculation is confirmed. The enthalpy difference,ΔH(gt), is determined to be 306(200) cal mol⁻¹ using the abundance of the trans conformer, 46(10)%.     

Structure and IR spectroscopic behaviour of 1,8-bis-(dimethylamino)naphthalene 2,4-dinitroimidazolate

The crystal structure of 1,8-bis(dimethylamino)naphthalene (DMAN) 2,4-dinitroimidazolate, C₁₇H₂₀N₆O₄, has been determined by X-ray diffraction. The crystals are monoclinic, P2 ₁/c, a = 13.426(4), b = 10.465(3), c = 15.915(4) », β = 126.12(4)°, Z = 4. The structure was solved by direct methods, and refined to an R value of 0.033 for 2291 non-zero independent amplitudes. The [NN⋯N]⁺ bridges of 2.606(3) » with ∠NHN = 160(3)° are characterized by an asymmetric proton density distribution. The IR protonic absorption is located in two regions at about 650 and 1950 cm⁻¹ showing relatively small intensity. The isotopic ratio ν(NHN/ν(NDN) for the low frequency region is almost unity. It seems that hydrogen bonds in protonated DMAN are characterized by a flat asymmetric single minimum potential for the proton motion.     

The molecular structure of the N-chloroimine product of rearrangement of N,N-dichloroperfluoroaniline: A study by gas-phase electron diffraction

A gas-phase electron-diffraction study of the product of rearrangement of N,N-dichloro-perfluoroaniline has assisted in establishing it to be the N-chloroimine, I, rather than the azepine, II. The molecule is found to be planar apart from atoms Cl13 and F14. The detailed dimensions shown in Fig. 2 were obtained by least-squares refinements in which several structural constraints were applied to reduce the total number of independent parameters. Of particular interest is the evidence for overcrowding around the CN bond: ∠N7C1C2 = 128°, ∠C18N7C1 = 126°, ∠N7C1C6 = 118° ; the distance C18 β F9 is 2.73 Å.     

The gas-phase structure of bis(fluorosulfonyl)difluoromethane, (SO2F)2CF2

New synthetic pathways and the infrared spectrum of bis(fluorosulfonyl)difluoromethane, (SO₂F)₂CF₂, are reported. The geometric structure and conformational properties of the title compound have been studied by gas electron diffraction. Depending on the rotational position of the two SO₂F groups, four conformers with different symmetries can occur in this compound: C_2v symmetry, if both S? F bonds stagger the CF₂ group. C₂ or C_s symmetry, if one S?O bond of each group staggers the CF₂ group. The experimental electron diffraction intensities can be fitted equally well with a C₁ conformer or with a mixture of C_2v, C₂ and C_s conformers, in a ratio of 3:2:5. The following geometric parameters (r_a distances, ∠_α angles with 3σ uncertainties) were derived: C? F = 1.340(6) Å, S?O = 1.412(2) Å, S? F = 1.550(3) Å, C? S = 1.848(4) Å, S? C? S = 113.6(7)°, F? C? F = 110.0(10)°, O?S?O = 124.6(18)°, C? S? F = 96.5(16)° and C? S?O = 108.4(14)°.     

Versatile reactivity of half-sandwich Ir and Rh complexes toward carboranylamidinates and their derivatives: synthesis, structure, and catalytic activity for norbornene polymerization

Synthesis, structure, and reactivity of carboranylamidinate‐based half‐sandwich iridium and rhodium complexes are reported for the first time. Treatment of dimeric metal complexes [{Cp*M(μ‐Cl)Cl}₂] (M=Ir, Rh; Cp*=η⁵‐C₅Me₅) with a solution of one equivalent of nBuLi and a carboranylamidine produces 18‐electron complexes [Cp*IrCl(Cab^N‐DIC)] ( 1 a ; Cab^N‐DIC=[iPrN?C(closo‐1,2‐C₂B₁₀H₁₀)(NHiPr)]), [Cp*RhCl(Cab^N‐DIC)] ( 1 b ), and [Cp*RhCl(Cab^N‐DCC)] ( 1 c ; Cab^N‐DCC=[CyN?C(closo‐1,2‐C₂B₁₀H₁₀)(NHCy)]). A series of 16‐electron half‐sandwich Ir and Rh complexes [Cp*Ir(Cab^N′‐DIC)] ( 2 a ; Cab^N′‐DIC=[iPrN?C(closo‐1,2‐C₂B₁₀H₁₀)(NiPr)]), [Cp*Ir(Cab^N′‐DCC)] ( 2 b , Cab^N′‐DCC=[CyN?C(closo‐1,2‐C₂B₁₀H₁₀)(NCy)]), and [Cp*Rh(Cab^N′‐DIC)] ( 2 c ) is also obtained when an excess of nBuLi is used. The unexpected products [Cp*M(Cab^N,S‐DIC)], [Cp*M(Cab^N,S‐DCC)] (M=Ir 3 a , 3 b ; Rh 3 c , 3 d ), formed through BH activation, are obtained by reaction of [{Cp*MCl₂}₂] with carboranylamidinate sulfides [RN?C(closo‐1,2‐C₂B₁₀H₁₀)(NHR)]S^? (R=iPr, Cy), which can be prepared by inserting sulfur into the C? Li bond of lithium carboranylamidinates. Iridium complex 1 a shows catalytic activities of up to 2.69×10⁶ g_PNB ${{\rm{mol}}_{{\rm{Ir}}}^{ - {\rm{1}}} }Synthesis, structure, and reactivity of carboranylamidinate-based half-sandwich iridium and rhodium complexes are reported for the first time. Treatment of dimeric metal complexes [{Cp*M(μ-Cl)Cl}(2)] (M = Ir, Rh; Cp* = η(5)-C(5)Me(5)) with a solution of one equivalent of nBuLi and a carboranylamidine produces 18-electron complexes [Cp*IrCl(Cab(N)-DIC)] (1?a; Cab(N)-DIC = [iPrN=C(closo-1,2-C(2)B(10)H(10))(NHiPr)]), [Cp*RhCl(Cab(N)-DIC)] (1?b), and [Cp*RhCl(Cab(N)-DCC)] (1?c; Cab(N)-DCC = [CyN=C(closo-1,2-C(2)B(10)H(10))(NHCy)]). A series of 16-electron half-sandwich Ir and Rh complexes [Cp*Ir(Cab(N')-DIC)] (2?a; Cab(N')-DIC = [iPrN=C(closo-1,2-C(2)B(10)H(10))(NiPr)]), [Cp*Ir(Cab(N')-DCC)] (2?b, Cab(N')-DCC = [CyN=C(closo-1,2-C(2)B(10)H(10)(NCy)]), and [Cp*Rh(Cab(N')-DIC)] (2?c) is also obtained when an excess of nBuLi is used. The unexpected products [Cp*M(Cab(N,S)-DIC)], [Cp*M(Cab(N,S)-DCC)] (M = Ir 3?a, 3?b; Rh 3?c, 3?d), formed through BH activation, are obtained by reaction of [{Cp*MCl(2)}(2)] with carboranylamidinate sulfides [RN=C(closo-1,2-C(2)B(10)H(10))(NHR)]S(-) (R = iPr, Cy), which can be prepared by inserting sulfur into the C-Li bond of lithium carboranylamidinates. Iridium complex 1?a shows catalytic activities of up to 2.69×10(6) g(PNB) mol(Ir)(-1) h(-1) for the polymerization of norbornene in the presence of methylaluminoxane (MAO) as cocatalyst. Catalytic activities and the molecular weight of polynorbornene (PNB) were investigated under various reaction conditions. All complexes were fully characterized by elemental analysis and IR and NMR spectroscopy; the structures of 1?a-c, 2?a, b; and 3?a, b, d were further confirmed by single crystal X-ray diffraction.     

Hydrogen bonding in 2‐amino‐4,6‐dimethoxypyrimidine, 2‐benzylamino‐4,6‐bis(benzyloxy)pyrimidine and 2‐amino‐4,6‐bis(N‐pyrrolidino)pyrimidine: chains of fused rings and a centrosymmetric dimer

Molecules of 2‐amino‐4,6‐di­methoxy­pyrimidine, C₆H₉N₃O₂, (I), are linked by two N—H?N hydrogen bonds [H?N 2.23 and 2.50 Å, N?N 3.106 (2) and 3.261 (2) Å, and N—H?N 171 and 145°] into a chain of fused rings, where alternate rings are generated by centres of inversion and twofold rotation axes. Adjacent chains are linked by aromatic π–π‐stacking interactions to form a three‐dimensional framework. In 2‐­benzylamino‐4,6‐bis(benzyloxy)pyrimidine, C₂₅H₂₃N₃O₂, (II), the mol­ecules are linked into centrosymmetric R(8) dimers by paired N—H?N hydrogen bonds [H?N 2.13 Å, N?N 2.997 (2) Å and N—H?N 170°]. Molecules of 2‐amino‐4,6‐bis(N‐pyrrolidino)­pyrimidine, C₁₂H₁₉N₅, (III), are linked by two N—H?N hydrogen bonds [H?N 2.34 and 2.38 Å, N?N 3.186 (2) and 3.254 (2) Å, and N—H?N 163 and 170°] into a chain of fused rings similar to that in (I).     

N-phosphonio formamidine derivatives: Synthesis,characterization, X-ray crystal structures,and deprotonation reactions

A simple and efficient method for the preparation of N-phosphonio formamidine derivatives of the general formula [R”₂N?C(H)=N?P(R’)R₂]⁺X^? is described. The data recorded in solution and the single crystal X-ray studies revealed that these compounds are best described by the combination of the two mesomeric N-phosphonio formamidine [R”₂N?C(H)=N?P(R’)R₂]⁺ and iminium phosphazene [R”₂N=C(H)?N=P(R’)R₂]⁺ forms. Formamidine phosphorus ylides ⁱPr₂N?C(H)=N?P(CH₂)R₂ were prepared after addition of ^tBuLi at –78 °C from the corresponding N-phosphonio compounds. [(PhCN)₂Pd(Cl)₂] was reacted with ⁱPr₂N?C(H)=N?P(CH₂)ⁱPr₂ to form the dimeric complex [(ⁱPr₂N?C(H)=N?P(CH₂)ⁱPr₂)Pd(Cl)(μ-Cl)]₂ which was structurally characterized by X-ray analysis. The deprotonation reactions conducted on [ⁱPr₂N?C(H)=N?PPh₃]⁺X^? occurred via an intramolecular rearrangement to give the cyanamide compound ⁱPr₂N?C≡N and PPh₃; transient formation of the amino-phosphazene-carbene ⁱPr₂N?C?N=PPh₃ was not observed.