Spectroscopic Detection Of Low-Valent Phosphorus Compounds Phosphorus Compounds

Low-valent phosphorus compounds(RP,RPO)are a kind of active insertion intermediates,which have the characteristics of high reactivity and short life.Such transient species are difficult to study in traditional ways.Phosphinidene(RP)can form complexes with transition metals,and undergo cycloaddition reaction with olefins or carbene.It plays an important role in synthesis,catalysis and coordination chemistry.Phosphorus-containing compounds decompose into low-priced phosphorus-containing small molecules such as PO and PO2 at high temperature,so R-PO small molecules have wide application in flame-retardant materials.The low-valence phosphorus compounds mentioned in this paper(MeOP,MePO,FPO)are all obtained by decomposition of azide compounds.Phosphorus azide compounds are unstable at room temperature and easy to decompose,resulting in their synthesis,characterization and properties have always been difficult to study.In this paper,high-energy metastable MeOP(N3)2,its isomer MeP(O)(N3)2 and low-valent phosphorus small molecule FPO are taken as research objects,and their molecular structure,decomposition intermediates and reaction potential energy surface are comprehensively analyzed by means of micro-synthesis low-temperature cold trap separation platform,cryogenic Matrix-solation infrared spectroscopy,low-temperature matrix-paramagnetic resonance(EPR)and quantum chemical calculation assistance.The main work of this paper is as follows1.The photolysis and pyrolysis of azide MeOP(N3)2 were studied by matrix isolation technology.The first-time detection and observation of its isomerization with methoxyphosphinidene(MeOP).The azide precursor MeOP(N3)2 was irradiated with 266 nm laser and decomposed to produce unstable intermediate MeOP.The intermediate was irradiated with 193 nm laser to produce isomerized product MePO In order to determine the intermediate MePO,the matrix isolation experiment was carried out on MeP(O)(N3)2.MeP(O)(N3)2 lost three molecules of nitrogen after 193 nm laser irradiation to generate MePO and MeP(O)(N3)N intermediates,and MeP(O)(N3)N intermediates continued to be selectively irradiated(365 nm)to lose two molecules of nitrogen to generate MePO.The low temperature matrix isolation paramagnetic resonance technology was used to determine that MeP(O)(N3)N is a triplet state.However,in the low temperature matrix isolation pyrolysis experiment,MeP(O)(N3)2 lost three molecules of nitrogen to form MePO.Although MeOP can be isomerized to MePO under 193 nm illumination,MePO cannot be converted to MeOP under 193 nm illumination for a long time,that is,the process is irreversible.The conversion potential energy curves of MeOP and isomer MePO were analyzed by theoretical calculation method.2.The key intermediate FPO was identified after flash vacuum pyrolysis of FP(O)(N3)2.The oxidation reaction between FPO and O2 was studied by combining low-temperature matrix isolation spectroscopy,isotope labeling and quantum chemical calculation.The results show that FPO reacts with O2 to generate FPO2 and cyclic molecule FPO3.In addition to spectral identification of novel intermediates FPO2 and FPO3 in oxidation reaction,18O2 isotope experimental markers confirm that oxygen isotope exchange exists in oxidation reaction,which is verified by MECP theoretical method.