Studies of phosphorus compounds using the magnetic resonance spectra of nuclei other than phosphorus-31

Unsymmetrical bis-phosphorus ligands. IV. Group VI metal carbonyl derivatives of diphenylphosphinomethyl and diphenylphosphinomethyl phosphinites, (C6H5)2P(CH2)nOP(C6H5)2, n = 1 or 2, and an unusual phosphorus chemical shift chelate effect

“…The phosphorus-hydrogen coupling constants are generally higher for hydrogen on ß carbon than on a carbon. 26 Other bases for these assignments are discussed below.…”

Special Topics

“…1 ) Accumulation of halogen atoms on the same carbon also results in marked deshielding (entries [6][7][8][9]. Most of the generalizations that describe relative shielding in hydrocarbon groups 30 CF 3 CF 2 (2<) CF 2 (3() CF 2 (4) CF 2 (3) CF 2 (2) CF 3 F (4) 31 32 33 CF 3 CF 2 CF 2(2) CF 3 34 CF 2 -CF 2 35 Cvclo -C 6 have no applicability to fluorocarbon chains. Thus, in a saturated fluorocarbon, the CF 3 end groups are substantially deshielded as compared to the CF 2 groups (entries 18 and 30; 19 and 32); fluorines attached to unsaturated carbons vary over a wide shielding range (entries 22,23,25,29,34,38,42); and those attached to a carbon bearing a substituent other than fluorine may be markedly shielded as compared to fluorines on saturated chains (entries 37,40).…”

Through-space spin coupling between phosphorus and hydrogen in .pi.-C5H5W(CO)2PR3X (R = methyl, phenyl, methoxy, etc. X = iodine, trimethyltin)

“…Furthermore, metal complexes of phosphines can be regarded as being intermediate between the two above extremes [this is supported especially by measurements of V(31P-H) in PH3, (PH3)2W(CO)4, and PH4+] and so should exhibit values of 2/(31 • • '13C) which are close to zero since this coupling constant can vary monotonically from positive to negative as the hybridization of phosphorus changes. 5 The lack of coupling between phosphorus and the cyclopentadienyl ring carbons is therefore not abnormal and does not imply an absence of electronic interaction. In the light of this, the observed 3/(31 • • ) most reasonably arises from a mechanism involving the normal chemical bonds and there is no reason to postulate "through-space" interaction.…”