Microwave spectrum and structural parameters for the formamide-formic acid dimer

The rotational spectra for six isotopologues of the complex formed between formamide and formic acid have been measured using a pulsed-beam Fourier transform microwave spectrometer and analyzed to obtain rotational constants and quadrupole coupling parameters. The rotational constants and quadrupole coupling strengths obtained for H (12)COOH-H(2) (14)NCOH are A = 5889.465(2), B = 2148.7409(7), 1575.1234(6), eQq(aa) = 1.014(5), eQq(bb) = 1.99(1), and eQq(cc) = -3.00(1)?MHz. Using the 15 rotational constants obtained for the H (13)COOH, HCOOD, DCOOH, and H(2) (15)NCHO isotopologues, key structural parameters were obtained from a least-squares structure fit. Hydrogen bond distances of 1.78 A? for R(O3?H1) and 1.79 A? for R(H4?O1) were obtained. The "best fit" value for the angle(C-O-H) of formic acid is significantly larger than the monomer value of 106.9° with an optimum value of 121.7(3)°. The complex is nearly planar with inertial defect Δ = -0.158?amu A?(2). The formamide proton is moved out of the molecular plane by 15(3)° for the best fit structure. Density functional theory using B3PW91, HCTH407, and TPSS as well as MP2 and CCSD calculations were performed using 6-311++G(d,p) and the results were compared to experimentally determined parameters.     

Observation of a double C-H···π interaction in the CH2ClF···HCCH weakly bound complex

The structure of the CH(2)ClF···HCCH dimer has been determined using both chirped-pulse and resonant cavity Fourier-transform microwave spectroscopy. The complex has C(s) symmetry and contains both a double C-H···π interaction, in which one π-bond acts as acceptor to two hydrogen atoms from the CH(2)ClF donor, and a weak C-H···Cl interaction, with acetylene as the donor. Analysis of the rotational spectra of four isotopologues (CH(2)(35)ClF···H(12)C(12)CH, CH(2)(37)ClF···H(12)C(12)CH, CH(2)(35)ClF···H(13)C(13)CH, and CH(2)(37)ClF-H(13)C(13)CH) has led to a structure with C-H···π distances of 3.236(6) ? and a C-H···Cl distance of 3.207(22) ?, in good agreement with ab initio calculations at the MP2/6-311++G(2d,2p) level. Both weak contacts are longer than those observed in similar complexes containing a single C-H···π interaction that lies in the C(s) plane; however, this appears to be the first double C-H···π contact to be studied by microwave spectroscopy, so there is little data for direct comparison. The rotational and chlorine nuclear quadrupole coupling constants for the most abundant isotopologue are: A = 5262.899(14) MHz, B = 1546.8074(10) MHz, C = 1205.4349(7) MHz, χ(aa) = 28.497(5) MHz, χ(bb) = -65.618(13) MHz, and χ(cc) = 37.121(8) MHz.     

Accurate determination of the structure of cyclohexane by femtosecond rotational coherence spectroscopy and ab initio calculations

We combine femtosecond time-resolved rotational coherence spectroscopy with high-level ab initio theory to obtain accurate structural information for the nonpolar molecules cyclohexane (C(6)H(12)) and cyclohexane-d(12) (C(6)D(12)). We measured the rotational B(0) and centrifugal distortion constants D(J), D(JK) of the v = 0 states of C(6)H(12) and C(6)D(12) to high accuracy, for example, B(0)(C(6)H(12)) = 4306.08(5) MHz, as well as B(v) for the vibrationally excited states ν(32), ν(6), ν(16) and ν(24) of C(6)H(12) and additionally ν(15) for C(6)D(12). To successfully reproduce the experimental RCS transient, the overtone and combination levels 2ν(32), 3ν(32), ν(32) + ν(6), and ν(32) + ν(16) had to be included in the RCS model calculations. The experimental rotational constants are compared to those obtained at the second-order M?ller-Plesset (MP2) level. Combining the experimental and calculated rotational constants with the calculated equilibrium bond lengths and angles allows determination of accurate semiexperimental equilibrium structure parameters, for example, r(e)(C-C) = 1.526 ± 0.001 ?, r(e)(C-H(axial)) = 1.098 ± 0.001 ?, and r(e)(C-H(equatorial)) = 1.093 ± 0.001 ?. The equilibrium C-C bond length of C(6)H(12) is only 0.004 ? longer than that of ethane. The effect of ring strain due to the unfavorable gauche interactions is mainly manifested as small deviations from the C-C-C, C-C-H(axial), and C-C-H(equatorial) angles from the tetrahedral value.     

The pure rotational spectrum of HPS (X̃1A'): chemical bonding in second-row elements

The pure rotational spectrum of HPS, as well as its (34)S and D isotopologues, has been recorded at microwave, millimeter, and submillimeter wavelengths, the first observation of this molecule in the gas phase. The data were obtained using a combination of millimeter direct absorption, Fourier transform microwave (FTMW), and microwave-microwave double-resonance techniques, which cover the total frequency range from 15 to 419 GHz. Quantum chemical calculations at the B3LYP and CCSD(T) levels were also performed to aid in spectral identification. HPS was created in the direct absorption experiment from a mixture of elemental phosphorus, H(2)S, and Ar carrier gas; DPS was produced by adding D(2). In the FTMW study, these species were generated in a pulsed discharge nozzle from PH(3) and H(2)S or D(2)S, diluted in neon. The spectra recorded for HPS and its isotopologues exhibit clear asymmetric top patterns indicating bent structures; phosphorus hyperfine splittings were also observed in HPS, but not DPS. Analysis of the data yielded rotation, centrifugal distortion, and phosphorus nuclear spin-rotation parameters for the individual species. The r(m) ((1)) structure for HPS, calculated from the rotational constants, is r(H-P) = 1.438(1) A?, r(P-S) = 1.9320(1) A?, and θ(H-P-S) = 101.85(9)°. Empirically correcting for zero-point vibrational effects yields the geometry r(e)(H-P) = 1.4321(2) A?, r(e)(P-S) = 1.9287(1) A?, and θ(e)(H-P-S) = 101.78(1)°, in close agreement with the r(m) ((1)) structure. A small inertial defect was found for HPS indicating a relatively rigid molecule. Based on these data, the bonding in this species is best represented as H-P=S, similar to the first-row analog HNO, as well as HNS and HPO. Therefore, substitution of phosphorus and sulfur for nitrogen and oxygen does not result in a dramatic structural change.     

The ground-state rotational spectrum and molecular geometry of ethynylstannane

The ground-state rotational spectra of 24 isotopomers of ethynylstannane have been observed by pulsed-jet, Fourier-transform microwave spectroscopy. The spectroscopic constants, B(0,)D(J) and D(JK) are reported for symmetric-top isotopomers H(3)(n)Sn(12)C(12)CH, where n = 116, 117, 118, 119, 120, 122 and 124, D(3)(n)Sn(12)C(12)CH, where n = 116, 118, 120, 122 and 124, H(3)(n)Sn(13)C(12) CH and H(3)(n)Sn(12)C(13)CH , where n = 116,118 and 120, and H(3)(n)Sn(12)C(12)CD, where n = 116, 118 and 120. In addition, the values of A(0), B(0), C(0), Delta(J) and Delta(JK) were obtained for the three asymmetric-top isotopomers DH(2)(n)Sn(12)C(12)CH, where n = 116, 118 and 120. Hyperfine structure was resolved and assigned in the transitions of the isotopomers H(3)(n)SnCCD, where n = 116, 118 and 120, and in the isotopomers H(3)(117)SnCCH and H(3)(119)SnCCH. In the former group, the hyperfine structure arises from D nuclear quadrupole coupling while in the latter group its origin lies in the spin-rotation coupling of the I = 1/2 Sn nuclear spin to the rotational motion. For these isotopomers, D nuclear quadrupole and spin-rotation coupling constants are determined where appropriate. The rotational constants obtained for the 24 isotopomers of H(3)SnCCH were used to obtain the following types of molecular geometry for ethynylstannane: r(0), r(s), and r(m).     

High-resolution microwave spectrum of the weakly bound helium-pyridine complex

High-resolution rotational spectra of the helium-pyridine dimer were obtained using a pulsed molecular beam Fourier transform microwave spectrometer. Thirty-nine R-branch (14)N nuclear quadrupole hyperfine components of a- and c-type dipole transitions were observed and assigned. The following spectroscopic parameters were obtained: rotational constants A=3875.2093(48) MHz, B=3753.2514(45) MHz, and C=2978.4366(81) MHz; quartic centrifugal distortion constants D(J)=0.124 08(55) MHz, D(JK)=0.1200(43) MHz, D(K)=-0.2451(25) MHz, d(1)=0.004 27(27) MHz, and d(2)=0.000 16(10) MHz; sextic centrifugal distortion constants H(J)=0.003 053(35) MHz, H(JK)=-0.006 598(47) MHz, and H(K)=0.004 11(59) MHz; (14)N nuclear quadrupole coupling constants chi(aa)((14)N)=-4.7886(76) MHz, chi(bb)((14)N)=1.4471(76) MHz, and chi(cc)((14)N)=3.3415(43) MHz. Our analyses of the rotational and (14)N quadrupole coupling constants show that the He atom binds perpendicularly to the aromatic plane of C(5)H(5)N with a displacement angle of approximately 7.0 degrees away from the c axis of the pyridine monomer, toward the nitrogen atom. Results from an ab initio structure optimization on the second order Moller-Plesset level are consistent with this geometry and gave an equilibrium well depth of 86.7 cm(-1).     

Characterisation of H2S···CuCl and H2S···AgCl isolated in the gas phase: a rigidly pyramidal geometry at sulphur revealed by rotational spectroscopy and ab initio calculations

Pure rotational spectra of the ground vibrational states of eight isotopologues of H(2)S···CuCl and twelve isotopologues of H(2)S···AgCl have been analysed allowing rotational constants and hyperfine coupling constants to be determined. The molecular structures have been determined from the measured rotational constants and are presented alongside the results of calculations at the CCSD(T) level. Both molecules have C(s) symmetry at equilibrium and are pyramidal at the sulphur atom. The chlorine, metal, and sulphur atoms are collinear while the local C(2) axis of the hydrogen sulphide molecule intersects the axis defined by the heavy atoms at an angle, φ = 74.46(2)° for Cu and φ = 78.052(6)° for Ag. The molecular geometries are rationalised using simple rules that invoke the electrostatic interactions within the complexes. Centrifugal distortion constants, Δ(J), and nuclear quadrupole coupling constants, χ(aa)(Cu) and χ(aa)(Cl) for H(2)S···CuCl are presented for the first time. The geometry of H(2)S···AgCl is determined with fewer assumptions and greater precision than previously.     

Polyoxometalate Derivatives with Multiple Organic Groups. 2. Synthesis and Structures of Tris(organotin) alpha, beta-Keggin Tungstosilicates

Eight tris(organotin)-substituted Keggin tungstosilicate heteropolyanions have been synthesized and characterized by elemental analysis, infrared and M?ssbauer spectroscopy, multinuclear NMR, and X-ray crystallography. The new anions contain alpha- or beta-SiW(9)O(34)(10)(-) moieties and are of two structural types, [(RSn)(3)(SiW(9)O(37))](7)(-) (R, isomer: Ph, alpha-, 1; n-Bu, alpha-, 2; Ph, beta-, 3; n-Bu, beta-, 4) and [(RSnOH)(3)(SiW(9)O(34))(2)](14)(-) (Ph, alpha-, 5; n-Bu, alpha-, 6; Ph, beta-, 7; n-Bu, beta-, 8). Crystals of Cs(4)H(3)[(PhSn)(3)(SiW(9)O(37))].8H(2)O (anion 3) are monoclinic, space group C2/c, with lattice constants a = 48.91(2) ?, b = 12.111(3) ?, c = 20.334(9) ?, beta = 102.30 degrees, and Z = 8. The anion has nominal C(3)(v)() symmetry and has a structure with three corner-shared WO(6) octahedra of the beta-Keggin anion replaced by three PhSnO(5) groups. Crystals of Cs(9)H(5)[(BuSnOH)(3)(SiW(9)O(34))(2)].36H(2)O (anion 6) are tetragonal, space group P&fourmacr;2(1)m, with lattice constants a = b = 29.005(4) ?, c = 13.412(4) ?, and Z = 4. The anion has the anticipated D(3)(h)() symmetry and contains three BuSnOH groups sandwiched between A,alpha-SiW(9)O(34)(10)(-) anions.     

Synthesis, characterization and magnetic properties of four new organically templated metal sulfates [C5H14N2][M(II)(H2O)6](SO4)2, (M(II) = Mn, Fe, Co, Ni)

A series of novel organically templated metal sulfates, [C(5)H(14)N(2)][M(II)(H(2)O)(6)](SO(4))(2) with (M(II) = Mn (1), Fe (2), Co (3) and Ni (4)), have been successfully synthesized by slow evaporation and characterized by single-crystal X-ray diffraction as well as with infrared spectroscopy, thermogravimetric analysis and magnetic measurements. All compounds were prepared using a racemic source of the 2-methylpiperazine and they crystallized in the monoclinic systems, P2(1)/n for (1, 3) and P2(1)/c for (2,4). Crystal data are as follows: [C(5)H(14)N(2)][Mn(H(2)O)(6)](SO(4))(2), a = 6.6385(10) ?, b = 11.0448(2) ?, c = 12.6418(2) ?, β = 101.903(10)°, V = 906.98(3) ?(3), Z = 2; [C(5)H(14)N(2)][Fe(H(2)O)(6)](SO(4))(2), a = 10.9273(2) ?, b = 7.8620(10) ?, c = 11.7845(3) ?, β = 116.733(10)°, V = 904.20(3) ?(3), Z = 2; [C(5)H(14)N(2)][Co(H(2)O)(6)](SO(4))(2), a = 6.5710(2) ?, b = 10.9078(3) ?, c = 12.5518(3) ?, β = 101.547(2)°, V = 881.44(4) ?(3), Z = 2; [C(5)H(14)N(2)][Ni(H(2)O)(6)](SO(4))(2), a = 10.8328(2) ?, b = 7.8443(10) ?, c = 11.6790(2) ?, β = 116.826(10)°, V = 885.63(2) ?(3), Z = 2. The three-dimensional structure networks for these compounds consist of isolated [M(II)(H(2)O)(6)](2+) and [C(5)H(14)N(2)](2+) cations and (SO(4))(2-) anions linked by hydrogen-bonds only. The use of racemic 2-methylpiperazine results in crystallographic disorder of the amines and creation of inversion centers. The magnetic measurements indicate that the Mn complex (1) is paramagnetic, while compounds 2, 3 and 4, (M(II) = Fe, Co, Ni respectively) exhibit single ion anisotropy.     

The rotational spectrum of CuCCH(X̃ 1Σ+): a Fourier transform microwave discharge assisted laser ablation spectroscopy and millimeter/submillimeter study

The pure rotational spectrum of CuCCH in its ground electronic state (X? (1)Σ(+)) has been measured in the frequency range of 7-305 GHz using Fourier transform microwave (FTMW) and direct absorption millimeter/submillimeter methods. This work is the first spectroscopic study of CuCCH, a model system for copper acetylides. The molecule was synthesized using a new technique, discharge assisted laser ablation spectroscopy (DALAS). Four to five rotational transitions were measured for this species in six isotopologues ((63)CuCCH, (65)CuCCH, (63)Cu(13)CCH, (63)CuC(13)CH, (63)Cu(13)C(13)CH, and (63)CuCCD); hyperfine interactions arising from the copper nucleus were resolved, as well as smaller splittings in CuCCD due to deuterium quadrupole coupling. Five rotational transitions were also recorded in the millimeter region for (63)CuCCH and (65)CuCCH, using a Broida oven source. The combined FTMW and millimeter spectra were analyzed with an effective Hamiltonian, and rotational, electric quadrupole (Cu and D) and copper nuclear spin-rotation constants were determined. From the rotational constants, an r(m)(2) structure for CuCCH was established, with r(Cu-C) = 1.8177(6)?A?, r(C-C) = 1.2174(6)?A?, and r(C-H) = 1.046(2)?A?. The geometry suggests that CuCCH is primarily a covalent species with the copper atom singly bonded to the C≡C-H moiety. The copper quadrupole constant indicates that the bonding orbital of this atom may be sp hybridized. The DALAS technique promises to be fruitful in the study of other small, metal-containing molecules of chemical interest.     

Characterization of C-H...π interactions in the structure of the CHClF(2)-HCCH weakly bound complex

The microwave spectra of four isotopologues of the CHClF(2)-HCCH dimer have been measured and used to determine the structure of the complex. An initial scan over the 7-18 GHz region using the chirped-pulse microwave spectrometer at the University of Virginia provided initial assignments of the (35)Cl and (37)Cl isotopologues, with two additional H(13)C(13)CH species assigned using the resonant cavity Balle-Flygare microwave spectrometer at Eastern Illinois University. For the most abundant isotopologue, the rotational constants and quadrupole coupling constants are: A = 3301.21(4) MHz, B = 1353.4268(19) MHz, C = 1153.7351(18) MHz, χ(aa) = 34.681(12) MHz, χ(bb) = -69.70(3) MHz, χ(cc) = 35.02(2) MHz and χ(ab) = -8.8(3) MHz, in good agreement with ab initio calculations at the MP2/6-311++G(2d,2p) level. The alignment of CHClF(2) with respect to acetylene reveals a C-Hπ interaction, with a secondary C-ClH-C interaction also present between the two monomers. The fitted distance between the CHClF(2) hydrogen atom and the center of the triple bond is 2.730(6) ?, the distance between the chlorine atom and the acetylenic hydrogen is 3.061(38) ?, and the C-Hπ angle is 148.2(6)°. In addition, the centrifugal distortion constants give an estimate of the binding energy for the weak interaction of about 4.9(5) kJ mol(-1), in reasonable agreement with several similar complexes.     

Reactivity of trans-[PtX(2)(ketoxime)(2)] Complexes toward m-Chloroperoxybenzoic Acid: An Efficient Route to Coordinated Nitrosoalkanes and Solvent Dependence of the Reaction

The platinum(II) compounds trans-[PtX(2)(RR'C=NOH)(2)] [X = Cl, R = R' = Me, RR' = (CH(2))(4), (CH(2))(5); X = Br, R = R' = Me] react with m-chloroperoxybenzoic acid (MCPBA) in dimethylformamide to give the platinum(II) complexes [PtX(2){N(=O)CRR'ONCRR'}] containing coordinated nitrosoalkane ligands. The complexes [PtX(2){N(=O)CRR'ONCRR'}] were characterized by elemental analysis, EI-MS, IR, electronic absorption, and (1)H NMR spectroscopy; X-ray structure analysis was performed for [PtCl(2){N(=O)CC(5)H(10)ONCC(5)H(10)}]. The latter compound crystallizes in the triclinic P&onemacr; space group with a = 9.214(2) ?, b = 9.577(2) ?, c = 10.367(2) ?, alpha = 109.14(2) degrees, beta = 91.87(2) degrees, gamma = 115.62(2) degrees, V = 762.8(3) ?(3), Z = 2, and rho(calcd) = 2.135 g cm(-)(3). The reaction between trans-[PtX(2)(RR'C=NOH)(2)] and MCPBA displays a solvent dependence: interaction of these reagents in ketones, R(1)R(2)C=O, yields the platinum(IV) chelates [PtX(2)(OCR(1)R(2)ON=CRR')(2)], while the oxidation state of the oxime N atom remains unchanged. Heating [PtCl(2)(OCR(1)R(2)ON=CRR')(2)] in DMF or in DMF-d(7) at 100 degrees C leads to the extrusion of R(1)R(2)C=O and the formation of [PtCl(2){N(=O)CRR'ONCRR'}].     

On the weak O-H···halogen hydrogen bond: a rotational study of CH3CHClF···H2O

We measured the molecular beam Fourier transform microwave spectra of six isotopologues of the 1?:?1 adduct of CH(3)CHClF with water. Water prefers to form an O-H···F rather than an O-H···Cl hydrogen bond. This is just the contrary of what was observed in the chlorofluoromethane-water adduct, where an O-H···Cl link was formed (W. Caminati, S. Melandri, A. Maris and P. Ottaviani, Angew. Chem., Int. Ed., 2006, 45, 2438). The water molecule is linked with an O-H···F bridge to the fluorine atom, with r(F···H(w)) = 2.14 ?, and with two C-H···O contacts to the alkyl hydrogens with r(C(1)-H(1)···O(w)) = 2.75 ? and r(C(2)-H(2)···O(w)) = 2.84 ?, respectively. Besides the rotational constants, the quadrupole coupling constants of the chlorine atom have been determined. In addition, information on the internal dynamics has been obtained.     

Coordination Compounds of Schiff-Base Ligands Derived from Diaminomaleonitrile (DMN): Mononuclear, Dinuclear, and Macrocyclic Derivatives

Copper(II) and V(IV)O complexes of an open chain (1:2) Schiff-base ligand (H(2)L1), derived by the template condensation of diaminomaleonitrile (DMN) and salicylaldehyde, and dicopper(II) complexes of (2:2) macrocyclic Schiff-base ligands derived by template condensation of diformylphenols and diaminomaleonitrile, have been synthesized and studied. Structures have been established for the first time for mononuclear Cu(II) and V(IV)O derivatives of the open chain ligand H(2)L1 (1:2), a dinuclear macrocyclic Cu(II) complex derived from a 2:2 macrocyclic ligand (H(2)M1), and the half-condensed 1:1 salicylaldehyde ligand (H(2)L2). [Cu(L1)] (1) (L1 = C(18)H(10)N(4)O(2)) crystallized in the monoclinic system, space group P2(1)/n (No. 14), with a = 11.753(6) ?, b = 7.708(5) ?, c = 16.820(1) ?, and Z = 4. [VO(L1)(DMSO] (2) crystallized in the orthorhombic system, space group Pbca (No. 61), with a = 22.534(9) ?, b = 23.31(1) ?, c = 7.694(5) ?, and Z = 8. H(2)L2 (C(18)H(8)N(4)O) (3) crystallized in the monoclinic system, space group P2(1)/c (No. 14), with a = 13.004(6) ?, b = 11.441(7) ?, c = 7.030(4) ?, and Z = 4. [Cu(2)(M3)](CH(3)COCH(3)) (4) (M3 = C(32)H(24)N(8)O(4)) crystallized in the monoclinic system, space group C2/c (No. 15), with a = 38.33(2) ?, b = 8.059(4) ?, c = 22.67(2) ?, and Z = 8. [Cu(L3)(DMSO)] (5) (L3 = C(20)H(14)N(2)O(4)) crystallized in the triclinic system, space group P&onemacr; (No. 2), with a = 10.236(4) ?, b = 13.514(4) ?, c = 9.655(4) ?, and Z = 2. 4 results from the unique addition of two acetone molecules to two imine sites in [Cu(2)(M1)](ClO(4))(2) (M1 = 2:2 macrocyclic ligand derived from template condensation of DMN and 2,6-diformyl-4-methylphenol). 4 has extremely small Cu-OPh-Cu bridge angles (92.0, 92.8 degrees ), well below the expected lower limit for antiferromagnetic behavior, but is still antiferromagnetically coupled (-2J = 25.2 cm(-)(1)). This behavior is associated with a possible antiferromagnetic exchange term that involves the conjugated framework of the macrocyclic ligand itself. The ligand L3 in 5 results from hydrolysis of M1 on recrystallization of [Cu(2)(M1)](ClO(4))(2) from undried dimethyl sulfoxide.     

Unusual Reactivity Mode of Coordinated Oximes: Platinum(IV)-Assisted Ring Closure by Reaction with Acetone

The platinum(II) complexes trans-[PtCl(2)(RR'C=NOH)(2)], where R = R' = Me, RR' = (CH(2))(4) and (CH(2))(5), react with m-chloroperoxybenzoic acid in Me(2)CO to give the platinum(IV) complexes [PtCl(2)(OCMe(2)ON=CRR')(2)] in 50-60% yields. The complexes [PtCl(2)(OCMe(2)ON=CRR')(2)] were characterized by elemental analysis, EI-MS, and IR and Raman spectroscopies; X-ray structure analyses were performed for both trans-[PtCl(2)(OCMe(2)ON=CC(4)H(8))(2)] and trans-[PtCl(2)(OCMe(2)ON=CC(5)H(10))(2)]. The former compound crystallizes in the triclinic space group P&onemacr; with a = 8.088(2) ?, b = 8.327(2) ?, c = 8.475(2) ?, alpha = 103.54(3) degrees, beta = 102.15(3) degrees, gamma = 108.37(3) degrees, V = 501.0(2) ?(3), Z = 1, and rho(calcd) = 1.917 g cm(-)(3). The latter complex crystallizes in the monoclinic space group C2/c with a = 12.5260(10) ?, b = 9.3360(10) ?, c = 18.699(2) ?, beta = 98.320(10) degrees, V = 2163.7(4) ?(3), Z = 4, and rho(calcd) = 1.862 g cm(-)(3). The structures of [PtCl(2)(OCMe(2)ON=CC(4)H(8))(2)] and [PtCl(2)(OCMe(2)ON=CC(5)H(10))(2)] show an octahedron of Pt where two Cl atoms and two chelate ligands are mutually trans, respectively.     

Synthesis and Characterization of a New Alkenyldecaborane and Alkenyl Monocarbon Carboranes

Decaborane(14) reacts with 1-(CH(3))(3)SiC&tbd1;CC(4)H(9) in the presence of dimethyl sulfide to give the new alkenyldecaborane 5-(S(CH(3))(2))-6-[(CH(3))(3)Si(C(4)H(9))C=CH]B(10)H(11) (I). Crystal data for 5-(S(CH(3))(2))-6-[(CH(3))(3)Si(C(4)H(9))C=CH]B(10)H(11): space group P2(1)/n, monoclinic, a = 9.471(1) ?, b = 13.947(3) ?, c = 17.678(3) ?, beta = 100.32(1) degrees. A total of 3366 unique reflections were collected over the range 2.0 degrees /= 3sigma(F(o)(2)) and were used in the final refinement. R(F)() = 0.083; R(w)(F)() = 0.094. The single-crystal X-ray structure of 5-(S(CH(3))(2))-6-[((CH(3))(3)Si)(2)C=CH]B(10)H(11) (A) is also reported. Crystal data for 5-(S(CH(3))(2))-6-[((CH(3))(3)Si)(2)C=CH]B(10)H(11): space group, P2(1)2(1)2(1), orthorhombic, a = 9.059 (3) ?, b = 12.193(4) ?, c = 21.431(3) ?. A total of 4836 unique reflections were collected over the range 6 degrees /= 3sigma(F(o)(2)) and were used in the final refinement. R(F)() = 0.052; R(w)(F)() = 0.059. The reactions of 5-(S(CH(3))(2))6-[(CH(3))(3)Si(C(4)H(9))C=CH]B(10)H(11) and 5-(S(CH(3))(2))6-[((CH(3))(3)Si)(2)C=CH]B(10)H(11) with a variety of alkyl isocyanides were investigated. All of the alkenyl monocarbon carboranes reported are the result of incorporation of the carbon atom from the isocyanide into the alkenyldecaborane framework and reduction of N&tbd1;C bond to a N-C single bond. The characterization of these compounds is based on (1)H and (11)B NMR data, IR spectroscopy, and mass spectrometry.     

Syntheses and Structural Characterization of Tetrahedral Four-Coordinate Gold(I) Complexes of 1,3,5-Triaza-7-phosphaadamantane. An Example of a Hydrogen-Bond-Directed Supramolecular Assembly

The synthesis and structural characterization of water-soluble four-coordinate gold(I) complexes containing monodentate phosphine ligands are described. The ligands used are 1,3,5-triaza-7-phosphaadamantane (TPA) and its protonated and methylated derivatives, [HTPA]Cl and [MeTPA]I. Formation of the four-coordinate gold(I) species is favored by the small cone angle of the phosphine (102 degrees ) and its ability to form a hydrogen-bonded network between the nitrogen atoms of the ligand and solvent water molecules. The gold center in all four complexes has a nearly regular tetrahedral geometry with an average P-Au-P angle of 109.5 degrees. [(HTPA)(3)(TPA)Au](PF(6))(4).4H(2)O.CH(3)CN(1) crystallizes in the monoclinic space group P2(1)/c (No. 14) with cell constants a = 20.719(3) ?, b = 15.606(2) ?, c = 17.854(2) ?, beta = 114.03(1) degrees, and Z = 4. Refinement of 4977 reflections and 650 parameters yields R = 0.0396 and R(w) = 0.0500. [(TPA)(4)Au]PF(6).1.5HCl.H(2)O (2), crystallizes in the monoclinic space group C2/c (No. 15) with cell constants a = 33.036(7) ?, b = 11.212(2) ?, c = 31.503(5) ?, b = 137.58(1) degrees, and Z = 8. Refinement of 3835 reflections and 470 parameters yields R = 0.0351 and R(w) = 0.0403. [(TPA)(4)Au]Cl(4).6H(2)O (3) was characterized structurally in the cubic space group Fd&thremacr;m (No. 227) with cell constants a = b = c = 20.020(2) ? and Z = 8. Refinement of 290 reflections and 28 parameters yields R = 0.0624 and R(w) = 0.1291. [(MeTPA)(4)Au](PF(6))(5).2CH(3)CN (4) crystallizes in the monoclinic space group C2/c (No. 15) with cell constants a = 23.337(3) ?, b = 14.855(3) ?, c = 35.317(5) ?, b = 97.95(1) degrees, and Z = 8. Refinement of 7840 reflections and 621 parameters yields R = 0.0493 and R(w) = 0.0698.     

Femtosecond degenerate four-wave mixing of carbon disulfide: high-accuracy rotational constants

Femtosecond degenerate four-wave mixing (fs-DFWM) rotational coherence spectroscopy (RCS) has been used to determine the rotational and centrifugal distortion constants of the 00 (0)0 ground and 01 (1)0 vibrationally excited states of gas-phase CS(2). RCS transients were recorded over the 0-3300 ps optical delay range, allowing the observation of 87 recurrences. The fits yield rotational constants B(00 (0)0)=3.271 549 2(18) GHz for (12)C(32)S(2) and B(00 (0)0)=3.175 06(21) GHz for the (12)C(32)S(34)S isotopomer. The rotational constants of the degenerate 01 (1)0 bending level of (12)C(32)S(2) are B(01 (1)0)=3.276 72(40) and 3.279 03(40) GHz for the e and f substrates, respectively. These fs-DFWM rotational constants are ten times more accurate than those obtained by CO(2) laser/microwave heterodyne measurements and are comparable to those obtained by high-resolution Fourier transform infrared spectroscopy. Ab initio calculations were performed at two levels, second-order Moller-Plesset theory and coupled-cluster singles, doubles, and iterative triples [CCSD(T)]. The equilibrium and vibrationally averaged C=S distances were calculated using large Dunning basis sets. An extrapolation procedure combining the ab initio rotational constants with the experiment yields an equilibrium C=S bond length of 155.448 pm to an accuracy of +/-20 fm. The theoretical C=S bond length obtained by a complete basis set extrapolation at the CCSD(T) level is r(e)(C=S)=155.579 pm, or 0.13 pm longer than that in the experiment.     

The study for the incipient solvation process of NaCl in water: the observation of the NaCl-(H2O)n (n = 1, 2, and 3) complexes using Fourier-transform microwave spectroscopy

Pure rotational spectra of the sodium chloride-water complexes, NaCl-(H(2)O)(n) (n = 1, 2, and 3), in the vibronic ground state have been observed by a Fourier- transform microwave spectrometer coupled with a laser ablation source. The (37)Cl-isotopic species and a few deuterated species have also been observed. From the analyses of the spectra, the rotational constants, the centrifugal distortion constants, and the nuclear quadrupole coupling constants of the Na and Cl nuclei were determined precisely for all the species. The molecular structures of NaCl-(H(2)O)(n) were determined using the rotational constants and the molecular symmetry. The charge distributions around Na and Cl nuclei in NaCl are dramatically changed by the complex formation with H(2)O. Prominent dependences of the bond lengths r(Na-Cl) on the number of H(2)O were also observed. By a comparison with results of theoretical studies, it is shown that the structure of NaCl-(H(2)O)(3) is approaching to that of the contact ion-pair, which is considered to be an intermediate species in the incipient solvation process.