The photoelectron and microwave spectra of the unstable species thioacetaldehyde,CH3CHS,and thioacetone, (CH3)2CS

Combined photoelectron and microwave techniques have been used to study the unstable species thioacetaldehyde, CH₃CHS, and thioacetone, (CH₃)₂CS. These species are produced when their respective cyclic trimers, 1,3,5-trimethyl s-trithiane and hexamethyl s-trithiane, are pyrolysed. The trimer vapours are flowed at approximately 30 μ Hg pressure via a quartz tube heated to between 500 and 600°C into a photoelectron or microwave spectrometer. Under these low pressure conditions the lifetime of CH₃CHS was about 10 seconds. The lifetime of (CH₃)₂CS was much longer, of the order of several minutes.The first (vertical) ionisation potentials of thioacetaldehyde and thioacetone are 8.98 ± 0.02 eV and 8.60 ± 0.05 eV respectively. The photoelectron spectra of the parent trimers have also been studied as well as s-trithiane, the trimer of thioformaldehyde. The microwave rotational spectra show evidence of hindered internal rotation. Preliminary analyses indicate that in thioacetaldehyde the barrier is 1545 ± 20 cal per mole (6470 joule per mole) and in thioacetone it is 1300 ± 50 cal per mole (5440 joule per mole).     

C60: Buckminsterfullerene,The Celestial Sphere that Fell to Earth

In 1975–1978 the long-chained polyynylcyanides, HC₅N, HC₇N, and HC₉N were surprisingly discovered in the cold dark clouds of interstellar space by radioastronomy. The subsequent quest for their source indicated that they were being blown out of red giant, carbon stars. In 1985 carbon-cluster experiments aimed at simulating the chemistry in such stars confirmed these objects as likely sources. During these cluster studies a serendipitous discovery was made; a stable pure-carbon species, C₆₀, formed spontaneously in a chaotic plasma produced by a laser focused on a graphite target. A closed spheroidal cage structure was proposed for this molecule, which was to become the third well-characterized allotrope of carbon and was named buckminsterfullerene. It has taken five years to produce sufficient material to prove the correctness of this conjecture. There may be a timely object lesson in the fact that exciting new and strategically important fields of chemistry and materials science have been discovered overnight due to fundamental research, much of which was unable to attract financial support, and all of which was stimulated by a fascination with the role of carbon in space and stars. In this account, interesting aspects of this discovery, its origins, and its sequel are presented. The story has many facets, some of which relate to the way scientific discoveries are made.     

The microwave spectrum of phosphabutadiyne, H---CC---CP

A detailed rotational analysis of the microwave spectrum between 26.5 and 40 GHz of phosphaethene, CH₂=PH, has been carried out. This molecule is the simplest member of a new class of unstable molecules—the phosphaalkenes. The species can be produced by pyrolysis of (CH₃)₂PH, CH₃PH₂ and also somewhat more efficiently from Si(CH₃)₃CH₂PH₂. Full first-order centrifugal distortion analyses have been carried out for both ¹²CH₂³¹PH and ¹²CH₂³¹PD yielding: A₀ = 138 503.20(21), B₀ = 16 418.105(26), and C₀ = 14 649.084(28) MHz for ¹²CH₂³¹PH. The 1₀₁-0₀₀ μ_A lines have also been detected for ¹³CH₂PH, cis-CDHPH and trans-CHDPH. These data have enabled an accurate structure determination to be carried out which indicates: r(H_cC) = 1.09 ± 0.015 Å, (H_cCP) = 124.4 ± 0.8°; r(H_tC) = 1.09 ± 0.015 Å, (H_tCP) = 118.4 ± 1.2°; r(CP) = 1.673 ± 0.002 Å, (HCH) = 117.2 ± 1.2°; r(PH) = 1.420 ± 0.006 Å, (CPH) = 97.4 ± 0.4°. The dipole moment components have been determined as μ_A = 0.731 (2), μ_B = 0.470 (3), μ = 0.869 (3) D for CH₂PH; μ_A = 0.710 (2), μ_B = 0.509 (10), μ = 0.874 (7) D for CH₂PD.     

Novel transition metal phospha-alkyne complexes: tBuCP acting as a 6 electron donor ligand. Synthesis,crystal and molecular structure of [Co2(CO)6(μ-tBuCP)W(CO)5]

A single crystal X-ray diffraction study of [Co₂(CO)₆(μ-^tBuCP)W(CO)₅] establishes that phospha-alkyne behaves as a 6e donor. Synthesis of the related [(η⁵-C₅H₅)₂Mo₂(CO)₄(μ-^tBuCP)W(CO)₅] complex is reported.     

Synthesis and 31P NMR spectra of some platinum(II) complexes of the phospha-alkene, (mesityl)P=CPh2: Crystal and molecular structure of cis-[PtCl2(PEt3)(C6H2Me3P=CPh2)]·CHCl3

Syntheses of the phospha-alkene complexes cis- and trans-[PtCl₂(PEt₃)(mesityl)P=CPh₂], and cis- [PtX₂{(Mesityl)P=CPh₂}₂](X=Cl, I, Me) complexes are reported. ³¹P NMR spectra indicate that bonding of the phospha-alkene to the metal is via the phosphorus lone pair and this is confirmed by a single crystal X-ray diffraction study of cis-[PtCl₂(PEt₃){(mesityl)P=CPh₂}]CHCl₃.     

The microwave spectrum,substitution structure,internal rotation barrier,and dipole moment of thioacetaldehyde,CH3CHS

The microwave rotational spectrum of the unstable species thioacetaldehyde, CH₃CHS, has been studied in a flow pyrolysis system. Eight isotopic variants have been studied allowing an accurate substitution structure to be derived. Most of the spectral lines show splittings due to internal rotation, analysis of which has allowed a barrier study to be made. For the torsional ground state of the most abundant species, V₃ = 1572 ± 30 cal/mole or 375.7 ± 7 J/mole. The dipole moment is μ = 2.33 ± 0.02 D with components μ_A = 2.26 ± 0.02 and μ_B = 0.56 ± 0.01 D.     

The microwave spectrum,structure, and quadrupole coupling constants of boron chloride difluoride,BCIF2

The microwave spectrum of boron chloride difluoride, BClF₂, has been investigated in the region 26.5–40.0 GHz. R-branch transitions belonging to the isotopic species ¹¹B³⁵Cl¹⁹F₂, ¹¹B³⁷Cl¹⁹F₂, and ¹⁰B³⁵Cl¹⁹F₂ have been observed and the derived rotational constants yield the following ground-state structural parameters: $\text{r}{}^0\text{(BF) = 1.315 ± 0.006}\text{A}\text{?}$, $\text{r}{}^{\mathrm{s}}\text{(BCl) = 1.728 ± 0.009}\text{A}\text{?}$, < FBF = 118.1 ± 0.5°. The ground-state rotational constants of the most abundant species ¹¹B³⁵Cl¹⁹F₂ are: A₀ = 10 449.32 ± 0.13, B₀ = 4705.811 ± 0.020, C₀ = 3239.702 ± 0.026 MHz, Δ_JK = 8.9 ± 1.7, and Δ_J = 1.86 ± 0.48 KHz. The asymmetry parameter κ = ?0.593291 and the inertial defect δ⁰ = 0.2361 amu Ų which is consistent with that expected for this type of molecule if planar. The ³⁵Cl quadrupole coupling constants for ¹¹B³⁵Cl¹⁹F₂ are χ_aa = ?42.8 ± 1.0, χ_bb = 30.2 ± 1.5, χ_cc = 12.6 ± 1.5 MHz with the asymmetry parameter η = 0.41.     

Carbon nanotube template promoted growth of NbS2 nanotubes/nanorods

NbS2 nanotubes/rods have been generated successfully employing carbon nanotube template promoted growth; high resolution transmission electron microscopy, coupled with EDX analysis, confirm the template effect and existence of NbS2 tube structures.     

The vibration-rotation spectrum of C-fluorophosphaethyne FCP: Fermi resonance and harmonic force field

The vibration-rotation bands of all the fundamentals and several overtone and combination vibrations of F¹²CP have been recorded. The C-F stretching fundamental ν₃ was observed in strong Fermi resonance with the overtone 2ν₂⁰; a similar resonance was also observed between ν₁ + ν₃ and ν₁ + 2ν₁⁰. The spectral analysis gave fundamental wavenumbers: ν₁ = 1670.842 (9), ν₂ = 375.428 (6), and ν₃ = 780.10 (22) cm⁻¹. The value of the equilibrium rotational constant B_e was found to be 0.1758943 (81) cm⁻¹. The harmonic force field for this molecule was derived from the wavenumbers of the three fundamentals and the l-doubling constant.