eng Oriental Scientific Publishing Company Biomedical and Pharmacology Journal 0974-6242 2016-04-28 9 1 133 142 10.13005/bpj/920 6508 article Niloufar Akbarzadeh-Torbati 1 Mehdi Shahraki 1 Department of Chemistry, University of Sistan and Baluchestan, P.O. Box 98135-674, Zahedan, Iran The crystal structure of di-t-butyl-(N-2-indolinone-1-yl)-3- (triphenylphosphoranylidene) succinate has been determined by X-ray crystallography. This ylide was crystallized in the monoclinic system with space group P21/n and cell parameters a=15.0375(6) Å, b = 11.5130(5) Å, c = 19.1325(8) Å, β = 101.577(4)°, V = 3245.0(2) ų, D_calc= 1.273 g.cm^-3 and Z = 4. The final R value is 0.0435 for 44084 reflections. This stable ylide existed as a mixture of two geometrical isomers in solution as a result of restricted rotation around the carbon-carbon partial double bond.  The X-ray study showed that adjacent carbonyl group in the ylide moiety of compound had a resonance with bond of C=P and also, intermolecular C-H…O hydrogen bonds were effective on stability of the crystal structure. In addition, the stability of the two Z- and E- isomers and the most important geometrical parameters have been elucidated by natural population analysis (NPA) and atoms in molecules (AIM) methods. https://biomedpharmajournal.org/vol9no1/assignment-of-the-major-geometrical-isomer-of-the-synthesized-stable-phosphorus-ylide-crystallography-and-theoretical-approaches/ Ylide X-ray Crystallography Isomer AIM NBO