Donor-Acceptor Complexes between Organoamines and Phosphorus Tribromide

Abstract

Hypervalence, Phosphines, Lewis Acid-Base AdductsLewis acid-base adducts between NMe3, tmeda (A^A^Af'-tetramethylethylenediamine), and 1.4-dimethylpiperazine as donors and PBr3 as acceptor have been prepared and structurally characterized. NMe3 and tmeda form 1:1 adducts (Me3 N)PBr3 (1) and (tmeda)PBr3 (2), re spectively, while 1,4-dimethylpiperazine adds 2 molecules of PBr3 leading to [(1,4-dimethylpiperazine)(PBr3):] (3). Adduct 2 is found in two modifications 2a and 2b with different crystal and molecular structures. (Crystal data of 1: monoclinic P2\/n, a = 5.983(3), b = 10.821(2), c = 13.877(5) Ä, ß = 99.70(2)°, Z = 4. 2a: monoclinic P2i/c, a = 7.891(1), b = 12.826(1), c = 12.218(2) A ,ß = 102.162(6)°, Z = 4. 2b: monoclinic P2]/n, a = 11.687(2), b = 8.375(1), c = 12.668(1) A, ß = 102.74(1)°, Z = 4. 3: monoclinic P2Jc, a = 6.383(3), b = 16.36(3), c = 8.407(3) A,ß= 101.49(2)°, Z= 2). The molecular structures of 1 and 2 indicate a partially ionic character with a strongly bonded amine and one (1 ) or two (2 ) weakly bonded bromine atoms. In 2 the donor tmeda is bonded through both nitrogen atoms to one phosphorus atom. In 3 the 1.4-dimethylpiperazine ring is in chair conformation, the methyl and PBr3 substituents being in equatorial and axial positions, respectively. Due to axial-axial repulsion the N-P donor-acceptor bonds are long while the P-Br bonds are rather uniform in length.

Sigma-Hole Interactions in Anion Recognition

“…As early as 2001, Mü ller and co-workers isolated a crystal structure showing intriguing PnB anion short contacts when investigating the donor-acceptor complexation reactions between N,N,N 0 ,N 0 -tetramethylethylenediamine (TMEDA) and phosphorus tribromide. 67 As shown in Figure 19A, two P$$$Br À short contacts (77% and 84% of P VdW P-Br radii) roughly collinear with each P-N covalent bond constituting the heterocycle 41 were evident. However, it was not until 2014 that Lin and coworkers performed the first computational study to assess the possibility of PnB 68 In all cases, Pn$$$X À interactions are shown in light blue.…”

Detailed comparison of the pnicogen bond with chalcogen, halogen, and hydrogen bonds

“…These systems are distinct from the gas phase studied by the theoretical calculations in that any such bonds are part of larger molecules, and further that they are surrounded by other molecules as well. Considering P···N pnicogen bonds first, when PBr 3 was paired with 1,4dimethylpiperazine, the two molecules were oriented [91] such that one of the Br atoms of PBr 3 lies directly opposite the N atom, with a θ(BrP···N) angle of 179.5º, and the N lone pair points directly toward the P atom. The intermolecular R(P···N) distance is 2.802 Å, very close to distances computed [58] for trihalogenated systems.…”

Zwitterionic Phosphoranides as Intermediates in the Reaction of Phosphorus Tribromide with N,N‐Dimethyl‐N′‐arylformamidines

“…Previously, we have shown that trivalent C-phosphorylated formamidines 7 cyclized into benzazaphospholes 9 in the presence of acids [9]. Now, we found that salt 15b bearing a pentavalent phosphorus substituent is transformed into 3Н-1,3-benzazaphosphole 10b upon melting (mp 151-152°С) or boiling its acetonitrile solution (Scheme 8).…”