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Phosphorus monoxide (. PO) is a key intermediate in phosphorus chemistry, and its association with the hydroxyl radical (. OH) to yield metaphosphorous acid (cis-HOPO) contributes to the chemiluminescence in the combustion of phosphines. When photolyzing cis-HOPO in an Ar-matrix at 2.8 K, the simplest dioxophosphorane HPO2 and an elusive hydroxyl radical complex (HRC) of . PO form. This prototypical radical-radical complex reforms into cis-HOPO at above 12.0 K by overcoming a barrier of 0.28±0.02 kcal mol-1 . The vibrational spectra of this HRC and its D- and 18 O-isotopologues suggest a structure of . OH⋅⋅⋅OP. , for which a triplet spin multiplicity with a binding energy of -3.20 kcal mol-1 has been computed at the UCCSD(T)-F12a/aug-cc-pVTZ level.

Chemical reactions involving quantum mechanical tunneling (QMT) increasingly attract the attention of natural scientists. In contrast to the hydrogen-tunneling as frequently observed in chemistry and biology, tunneling solely by heavy atoms is rare. Herein, we report the clear-cut heavy-atom tunneling in trifluoroacetyl nitrene, CF3C(O)N. Specifically, the carbonyl nitrene CF3C(O)N in the triplet ground state was generated in cryogenic matrices by laser (193 or 266 nm) photolysis of CF3C(O)N3 and characterized by IR and EPR spectroscopy. In contrast to the theoretically predicted activation barriers (> 10 kcal mol-1), CF3C(O)N undergoes rapid rearrangement into CF3NCO with half-life times of less than 10 minutes and unprecedentedly large 14N/15N kinetic isotope effects (1.18-1.33) in solid Ar, Ne, and N2 matrices even at 2.8 K. The tunneling disappearance of CF3C(O)N becomes much slower in the chemically active toluene and in 2-methyltetrahydrofuran at 5 K.

Neutral five-atomic cumulenes formally consisting of two pseudohalogens (e.g., NCO, NNN, NSO) by sharing the central nitrogen atom are exotic species that have been barely studied. Through flash vacuum pyrolysis of CF3S(O)NCO at ca. 1200 K, sulfinyl isocyanate, bearing resonance structures of O=C−N=S=O and O=C=N−S=O, has been generated in the gas phase and subsequently characterized in cryogenic matrices (Ar and N2). Its reversible conformational (syn and anti) interconversion and photodecomposition were observed.

The dipolar oxathiazyne-like sulfinylnitrene RS(O)N, a highly reactive α-oxo nitrene, has been rarely investigated. Upon flash vacuum pyrolysis of sulfinyl azide CF3S(O)N3 at 350 °C, an elusive sulfinylnitrene CF3S(O)N was generated in the gas phase in its singlet ground state and was characterized by matrix-isolation IR spectroscopy. Further fragmentation of CF3S(O)N at 600 °C produced CF3 and a novel iminyl radical OSN, an SO2 analogue, which were unambiguously identified by IR spectroscopy. Consistent with the experimental observations, DFT calculations clearly support a stepwise decomposition mechanism of CF3S(O)N3.

Die neuartige aromatische Ringverbindung 2,4-Diphospha-3,5-diazathiol (cyclo-SNPNP) wurde durch Blitzpyrolyse von SP(N3)3 und nachfolgende Matrixisolierung der Produkte erhalten und uber ihr IR-Spektrum und 15N-Isotopenmarkierung nachgewiesen. Quantenchemische Rechnungen lassen auf eine Bildung dieser Verbindung durch Kopf-zu-Schwanz-Dimerisierung von SNP mit anschliesender Abspaltung eines Schwefelatoms aus dem sehr instabilen, bootformigen, sechsgliedrigen Ring cyclo-SNPSNP schliesen.

Die UV-Photolyse (λ=248 oder 255 nm) von cyclischem S2N2, das in fester Argonmatrix isoliert wurde, ergibt zwei offenschalige S2N2-Isomere, trans-SNSN (3A′′) und cis-SNSN (3A′′), sowie das geschlossenschalige C2v-symmetrische Dimer (SN)2 (1A1). Die neuartigen Isomere wurden uber ihre IR-Spektren und ihre wechselseitige photolytische Umwandlung charakterisiert. Quantenchemische Rechnungen stutzen die experimentellen Ergebnisse und bieten Einblicke in die komplexe Potentialhyperflache von S2N2.