The Simplest Iminophosphane HPNH and Its Photoisomerization to Aminophosphinidene H2NP
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The simplest iminophosphane HPNH and aminophosphinidene H 2 NP are prototype molecules bearing phosphorus-nitrogen multiple bonds; however, both species remain hitherto unobserved. Here, we report the first time synthesis and characterization of HPNH and H 2 NP. Specifically, the cis and trans conformers of HPNH have been prepared in the gas phase by high-vacuum flash pyrolysis of di- tert -butylphosphanamine at ca. 950 K and subsequently isolated in solid N 2 -matrices at 10 K for the characterization by matrix-isolation IR (with D- and 15 N-isotope labeling) and UV-vis spectroscopy. In addition to the photo-induced conformational interconversion between trans -HPNH and cis -HPNH, their photoisomerization with H 2 NP has also been observed in the cryogenic matrices. In accordance with the very recently predicted lower energy of the singlet state than the triplet state by 0.2 kcal mol –1 for H 2 NP, its experimental IR spectrum shows good agreement with the calculations for the singlet state at the CCSD(T)-F12B/VTZ-F12 level using configuration-selective vibrational configuration interaction (VCI) theory. Upon photoexciation at 395 nm, the matrix-isolated H 2 NP reacts with CO and O 2 to yield H 2 NPCO and H 2 NPO 2 as the trapping and oxidation products, respectively.
