After the photoirradiation of (biphenyl-4-yl)chlorodiazirine (BCD) in ca. 10 K argon (Ar) matrices, the IR spectrum of (biphenyl-4-yl)chlorocarbene (BCC) was measured because the measured bands were in fair agreement with the bands obtained by vibration analysis. The photolyses of BCD-acetonitrile (MeCN)-Ar tricomponent matrices were also carried out to study the reaction of BCC with MeCN. For [MeCN]I [BCD] > 10, a spectrum that differed from BCC was obtained after the irradiation. The new bands are stable during the irradiation, during increasing temperature (to 45 K), and during storage. An 2-azonia-1-allenide type nitrile ylide (NY) structure was obtained in an optimization. Because the measured bands are in good agreement with those calculated using the vibration analysis for this NY structure, BCC adducts with MeCN immediately after the degradation of BCD.