Multinuclear magnetic resonance studies. Part 2. Diphosphanes and dithioxodi-λ⁵-phosphanes

Abstract

Carbon-I 3 and phosphorus-31 n.m.r. spectra have been obtained for a number of tetra-alkyldiphosphanes and tetraalkyldithioxodi-AS-phosphanes of general formulae ( R1R2P)z and [R1RzP(S)]2 respectively. Some analogous compounds with phenyl substituents have also been studied. Sateltite resonances in 31P resonance due to 13C-containing isotopomers have been examined. The data are treated, together with lH n.m.r. studies where appropriate, to obtain (P,P) and (P,C) coupling constants, as well as 13C and 31P chemical shifts. These n.m.r. parameters are discussed in terms of steric interactions and stereoisomerism. The values of I lJpp1 for both series of compounds increase markedly as the size of the substituents increases, and this effect correlates with an increase in aP.WITH the advent of Fourier-transform n.m.r. spectroscopy, it has become more feasible to study a range of nuclei, whereas in the past only lH, l9F, and, to some extent, 31P work was common. In particular the use of 13C n.m.r. has become widespread. Normally such spectra are recorded under proton-decoupled conditions and each type of 13C nucleus gives rise to a single peak. Splittings due to spin-spin coupling are usually only present when there are nuclei of spin & other than 13C and l H in the compound being studied. Such is the case for phosphorus-containing compounds, and this paper is concerned with the lH, 13C, and 31P n.m.r. spectra of a series of substituted diphosphanes, (I), and dithioxodi-A5-phosphanes, (11) .$ The data for tetramethyldiphosphane (I; R1 = R2 = Me) were published ear1ier.l Such compounds have been of interest (a) to n.m.r. spectroscopists because of the problems of spectral analysis for symmetrical spin systems 394 and because of the wide (and as yet unexplained) variation in the values of lJpp, and (b) to structural chemists because of the problem of internal rotation about the P-P bond.6 For the diphosphanes (I) themselves, the values of llJppl are normally very large,5 and the lH spectra are ' deceptively simple ',' yielding detailed information only when stringent experimental conditions are employed.s However, this is j-See also Part 1 of a related series.2For the use of An to indicate the connecting number ' n see IUPAC rules ' Nomenclature of Organic Chemistry: Section D.'

Formation of an imidazoliumyl-substituted [(LC)4P4]4+tetracation and transition metal mediated fragmentation and insertion reaction (LC= NHC)

“…Notably, Tamm and co-workers recently reported on the isolation of a diphosphene derivative obtained by the reduction of related dichlorophosphane with compound 6 21. The 31 P NMR spectrum of the reaction mixture shows only one major prominent intermediate with a singlet resonance at δ (P) = –29.1 ppm, which is in the range for diphosphanes 22. We assign this intermediate to dication 7 2+ which is similar to findings of Goicoechea and co-workers who isolated a related dibromo-diphosphane compound featuring imidazoliumyl-substituents 18.…”

Iron(II) High‐Spin and Low‐Spin Complexes from Pentaisopropylcyclopentadienyliron(II) Bis(trimethylsilyl)amide

“…Among these are [CpNb(CO) 2 (P 2 Ph 4 )] and the crystallographically characterized rhodium complex [{HC(MeC=NAr) 2 }Rh(η 2 ‐P 2 Ph 4 )] (Ar = ortho ‐diisopropylphenyl) . The triplet splitting of the iron hydride signal of [(C 5 i Pr 5 )FeH(P 2 Ph 4 )] ( 9 ) is a weak argument for bidentate diphosphine coordination, (see the Supporting Information, Figure S8). More meaningful is the 31 P chemical shift found for the two broad resonances at δ = 62.8 and 54.9 ppm for the tetraphenyldiphosphine complex 9 .…”

Phosphorus-31 nuclear magnetic resonance studies of solid diphosphine disulphides. Crystallographic considerations

“…This finding is in agreement with previously published solution-state results given in ref. (12), where a more detailed explanation may be found.…”