Hexacoordinate phosphorus. 6. Synthesis and characterization of neutral six-coordinate phosphorus(V) compounds derived from 2-pyridinol and related heteroatomic pyridine ligands

Dietmar K. Kennepohl, Ronald G. Cavell, A. Alan Pinkerton, Yoke Foo Lee

Research output: Contribution to journalJournal Articlepeer-review

15 Citations (Scopus)

Abstract

The reaction of the silylated form of the substituted pyridine ligands 2-(methylamino)pyridine, 2-hydroxypyridine, 2-mercaptopyridine, and 2,2′-dipyridylamine with X5-halogenophosphoranes yields, via trimethylsilyl halide elimination, a series of neutral hexacoordinate X6-phosphorus compounds (1-8), in which a four-membered chelate structure is achieved by donation of the electron pair from the pyridine nitrogen to phosphorus in addition to formation of P-O, P-N, or P-S bonds. The hexacoordinate nature of these compounds is evidenced by their high-field 31P NMR chemical shifts and is further substantiated by the crystal structure of Cl4P(NC5H4)NMe (1). Crystal data for 1: orthorhombic, space group P212121 (No. 19), a = 7.507 (3) k, b = 11.623 (3) A, c = 12.577 (2) k,V= 1097.4 A3, Z = 4. Final R and R., values for 1 are 0.038 and 0.045, respectively. The molecular structure shows also that the methylamino substituent of pyridine lies flat in the radial plane of the molecule, that the exocyclic nitrogen bound to phosphorus is planar, and that both the endocyclic (1.350 (6) A) and exocyclic (1.344 (6) A) C-N bond lengths have similar values which are furthermore indicative of C-N multiple bonding. P-Cl bond lengths range from 2.077 to 2.153 A, with the longest bonds being those perpendicular to the molecular plane and the shortest trans to the donating pyridine nitrogen. Saturation-transfer NMR experiments indicate that the fluorine exchange in F4P(NC5H4)NMe (2) involves two competitive processes of the opened-ring intermediate with similar energy barriers of 57.8 (1) (pseudorotation) and 56.1 (1) (ligand rotation) kJ/mol. Synthesis, selected reactions, and NMR spectral characterization of these compounds are reported.

Original languageEnglish
Pages (from-to)5088-5096
Number of pages9
JournalInorganic Chemistry
Volume29
Issue number25
DOIs
Publication statusPublished - 1990

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