Free Ethynylarsinidene and Ethynylstibinidene: Heavier Analogues of Nitrenes and Phosphinidenes.

Until now, there has been very little experimental evidence for the existence of free arsinidenes and stibinidenes, apart from the hydrides, AsH and SbH. Here, we report on photogeneration of triplet ethynylarsinidene, HCCAs, and triplet ethynylstibinidene, HCCSb, from ethynylarsine and ethynylstibine, respectively, in solid argon matrices. The products were identified using infrared spectroscopy and the associated UV absorption spectra are interpreted with the aid of theoretical predictions.

Unusual Quartet-Doublet Phosphorescence from the Phosphaethynyl Radical, CP.

We report the first detection of phosphorescence from the phosphaethynyl radical. This rare instance of quartet-doublet emission, studied here in solid argon, is presumably promoted by efficient intersystem crossing from the originally photoexcited doublet (B2 Σ+ ) to the adjacent second quartet state, 14 Δ. Vibronic progressions were traced for the a4 Σ+ -X2 Σ+ and a4 Σ+ -A2 Пi systems from their origins up to (v'=0)→(v''=5) and (v'=0)→(v''=2) bands, respectively. The measured phosphorescence lifetime is 108 ± 3 ms.

An Efficient Photochemical Route Towards Triplet Ethynylphosphinidene, HCCP.

While the archetypal free phosphinidene, H-P, has been studied for over a century, reports on uncomplexed, univalent phosphorus compounds are very sparse. Here we demonstrate production of HCCP in solid argon through the UV-induced rearrangement and subsequent dehydrogenation of phosphapropyne, CH3 CP. Migration of H atoms along the CCP backbone of CH3 CP resulted in production of the previously unobserved species 1-phosphapropadiene, CH2 =C=PH, followed by ethynylphosphine, HCCPH2 .