Base-Induced Dismutation of POCl₃ and POBr₃:  Synthesis and Structure of Ligand-Stabilized Dioxophosphonium Cations

Abstract

The interaction between POCl(3) or POBr(3) and pyridine or DMAP has been reinvestigated to clarify the discrepancies between previously published results concerning the Lewis acidity of phosphoryl halides and their behavior toward pyridine bases. The obtained results show that POCl(3) virtually does not react with pyridine, while it does with 4-(dimethylamino)pyridine (DMAP), even in SO(2) solution, to yield an ionic compound [(DMAP)(2)PO(2)]Cl.3SO(2) (1.3SO(2)). Its recrystallization from acetonitrile gives [(DMAP)(2)PO(2)]Cl.CH(3)CN (1.CH(3)CN). The POBr(3) reacts readily with both DMAP and pyridine forming the analogous tribromides, [(DMAP)(2)PO(2)]Br(3) (2) and [(py)(2)PO(2)]Br(3) (3), respectively. Treatment of 3 with Me(3)SiOSO(2)CF(3) in acetonitrile solution led to [(py)(2)PO(2)][CF(3)SO(3)].CH(3)CN (4), while the reaction between 1.CH(3)CN and Me(3)SiOPOF(2) gave [(DMAP)(2)PO(2)][PO(2)F(2)] (5). The crystal structures of 1.CH(3)CN, 1.3SO(2), 2, and 4 revealed that all four compounds are ionic containing the distorted tetrahedral cations [(DMAP)(2)PO(2)](+) and [(py)(2)PO(2)](+). Both ions represent a donor-stabilized form of the so far unknown cation [PO(2)](+). The geometry of [(DMAP)(2)PO(2)](+), optimized by density functional calculations at the B3LYP/6-31G(d,p) level, is in good agreement with X-ray structural data. The NBO analysis of natural atomic charges shows an extensive delocalization of the [PO(2)](+) intrinsic positive charge and indicates a contribution of the electrostatic attraction to the formation of N-P donor-acceptor bonds. According to a (31)P NMR study, the reactions of both phosphoryl halides with DMAP proceed via successive formation of the intermediates [(DMAP)POX(2)](+) and (DMAP)PO(2)X to give an equimolar mixture of [(DMAP)(2)PO(2)](+) and PX(5) (X = Cl, Br) as the end products. The NMR spectroscopic identification of the cations [(DMAP)POX(2)](+) and [(DMAP)(2)PO(2)](+) was supported by ab initio calculations of their chemical shifts.

Synthesis, structure, and magnetic properties of a family of copper(II) complexes and salts of isoquinoline: (Isoquinoline) Cu(X)2 [X = Cl, Br] and (isoquinolinium)2CuX4(H2O) [X = Cl, Br; n = 0,1]

“…These bond lengths and angles are comparable to those found in 3-bromo-1phenyl-1,2,3,4-tetrahydro-1,4-methanoquinolizinium tribromide 35 and 1,1'-phosphinicobis[4-(dimethylamino)pyridinium tribromide. 36 There are also quinoline-containing tribromide salts, such as quinolinium hexabromoantimonate(v) tribromide, 37 and copper containing tribromide salts, such as tris(5H-pyrido[3',2':4,5]cyclopenta[1,2-b]pyridine-5-one)-copper bis(tribromide) dibromide. 38 Although the bond lengths and angles are very similar, the independent nature of the two tribromide ions is clearly seen in the packing of the ions as there are short bromide… bromide contacts between symmetry related Br5-containing ions (the shortest being 3.804(3) Å), but the Br6-containing ions only exhibit short contacts with Br5-containing ions (the shortest being 3.975(3) Å) ( Fig.…”

Base‐Stabilized [PO]+/[PO2]+ Cations

“…Colorless crystals of 4 suitable for an X‐ray diffraction analysis were grown by diffusion of pentane into a DCM solution, and the formulation was confirmed as [(BAC) 2 PO 2 ][BF 4 ] (Figure a). The phosphorus of 4 adopts a distorted tetrahedral geometry, with the O1‐P1‐O2 angle of 123.5(2)° and C1‐P1‐C16 angle of 104.1(2)°, which is comparable to those in [(DMAP) 2 PO 2 ][Br 3 ] (126.8° and 99.4°) . The bond lengths of P1−C1 (1.828(5) Å) and P1−C16 (1.821(4) Å) are close to P−C single bond length in PPh 3 (average 1.83 Å), while the P−O bond lengths (1.474(3) and 1.473(3) Å) are even slightly shorter than that of the P=O double bond in O=PPh 3 (1.487(3) Å), close to those in [(DMAP) 2 PO 2 ][Br 3 ] (1.465(4) and 1.461(4) Å) …”

The Metaphosphite (PO2−) Anion as a Ligand

“…The P−O bond lengths (1.517(2)/1.512(2) Å) resemble those of free PO 2 − in the gas phase (1.50(1) Å) [5b] . Comparison with Lewis‐base stabilized PO 2 + species (1.46–1.47 Å) [10b–c] points at weaker P−O bonding in the anion. In turn, the reported PO 2 3− ligand (Figure 1 c) features one considerably longer, bridging P−O bond (1.58(3) Å).…”