Crystal structure of N-trifluoroacetyl-N′,N″-bis(N-cyclohexyl-methyl) phosphoric triamide, CF3C(O)N(H)P(O)[N(CH3)(C6H11)]2

Abstract

Source of materialThe title compound wass ynthesized by the reaction of N -trifluoroacetyl phosphoramidic dichloride (1.15 g, 5mmol) with Ncyclohexylmethyl amine (2.26 g, 20 mmol) in CCl 4 (10 mL)under 24 hours stirring at0°C.The solvent removed in vacuum and the solid washed with distilled water. The residue recrystallized in CH 3 CN.Singlecrystals of the compound were obtained from the solution of CH 3 CNafter aslow evaporation atroom temperature. DiscussionIsoelectronic analogues of common phosphorus(V)o xo acids, e.g., orthophosphoric acid H 3 PO4 ,m etaphosphoric acid HPO3 , and phosphonic acid H 3 PO3 ,inwhich the hydroxyl groups are replaced by N RR¢ moieties have been known for over acentury [1].Replacing amide group with N RR¢ forms N-acylated phosphoramides, R C(O)N(H)P(O) R 1 R 2 which are of speciali nterest because of: i) bearing aclose structuralr esemblance to the b -diketone frame, ii) usually acting aseffective chelating groups, iii) revealing of stoichiometry, structure and properties of coordination compounds which maybeclearly related with known types of metaldiketonates [2]. The title molecule contains one amidic hydrogen atom and form centrosymmetric dimers, produced by two equivalent intermolecularhydrogen bonds. The phosphoryl and the carbonyl groups are anti and the phosphorus atom in the structure hasslightly distorted tetrahedralcoordination. The bond angles around P1atom are in the range of 104.24(6)°-118.22(5)°, limited by the angles N3-P1-N1and O1-P1-N3, respectively.The bondl engths P1-N2and P1-N3are 1.634(1) Åand 1.628(1) Å,r espectively. They are significantly shorter thanthe typicalP-Nsingle bond length (1.77 Å) [3]. The bond length P1-N1(1.712(1) Å)is longer thanthe P1-N2and P1-N3due to the resonance interaction of N(amide) with the C = O-p system,t hatc auses apartial multiple-bond character in N1-C1, ( d (N1-C1) =1.355(2) Å. The other N-Cbond lengths are in the range of 1.467(2) Å-1.478(2) Å). The environment of N2and N3atoms indicates a slight deviation from planarity. Sum of the surrounding angles around N2and N3atoms are 356.4°and 358.5°. Furthermore, the angle C1-N1-P1is129.09(9)°. These results confirm the sp 2 hybridization for the nitrogen atoms, although due to the repulsion and steric interactions, some angles are greater and others are smaller than120°. The P = Obond length is 1.4782(8) Å,thatis larger thanthe normalP = Obond length (1.45 Å[3]) due to electron donating of the groups linked to Patom.