@article{f2aa55139dcb4e1da815c39219f1bc63,
title = "The first x-ray structure determination of a z-phosphaethylene: z-2-phenyl-1-(2,4,6-tri-t-butylphenyl)phosphaethylene",
abstract = "The sterically protected Z-phosphaethylene, Z-2-phenyl-1-(2,4,6-tri-t-butylphenyl)phosphaethylene (1-Z), was analyzed by X-ray crystallography.",
author = "Masaaki Yoshifuji and Kozo Toyota and Naoki Inamoto and Ken Hirotsu and Taiichi Higuchi",
note = "Funding Information: groups are arranged like a propeller around the P=C nodal plane making angles of 71{"}, 42.9{"}, and 36.6{"}, respectively. This conformation in 1-Z may be attained owing to the steric hindrance caused by the ortho-t-butyl groups. The P-C(l) bond distance is 1.674(2) w and is very close to that of HP=CH2 determined by microwave spectroscopy.7 The bulky aromatic ring is distorted to a boat form as has been observed in the compounds containing the 2,4,6-tri-t-butylphenyl-phosphorus group.8 It should be noted that the hydrogen atom bonded to C(3) and the bulky aryl group are extraordinarily close to each other: the distance between H(C3) and the mean benzene plane = 2.33(2) w and H(C3).*-C(8) = 2.42(2) ii. Unusual up-field chemical shift upto 6 6.1 observed for the aromatic protons in the 1H NMR of 1-Z might account for this situation. The widening of the P-C(l)-C(2) angle in 1-Z compared with the corresponding angle of 127.2{"} for the mesitylphosphaethylene might be due to this intramolecular repulsion. This is the first X-ray analysis9 of a very stable Z-phosphaethylene sterically protected by the extremely bulky 2,4,6-tri-t-butylphenyl group. Additionally 1 is the phosphaethylene with one hydrogen atom but without any hetero-atom substitution at C(1) in contrast to the hetherto known phospha-ethylenes,lf1° although the preparation of 1-(2.4,6-tri-t-butylphenyl)phosphaethylene has alreac:y 'Azen reported. 11 is also important that an appropriate bulkiness is essential for stabilization of such unusual compounds in low co-ordination state. Indeed Bickelhaupt et al. have recently reported unsuccessful results on their attempts to prepare trimesitylphosphaethylene.12 This work was supported in part by Scientific Research Grant-in-Aid from the Ministry of Education, Science and Culture of Japan and the Kurata Research Grant from the Kurata Foundation.13 We thank the Crystallographic Research Centre, Institute for Protein Research, Osaka University for X-ray data collection and computer calculations.",
year = "1985",
doi = "10.1016/S0040-4039(00)99022-1",
language = "English",
volume = "26",
pages = "6443--6446",
journal = "Tetrahedron Letters",
issn = "0040-4039",
publisher = "Elsevier Ltd.",
number = "52",
}