Heavy metal spin‐ ½ nuclei. Platinum‐195 relaxation times in phosphorus‐platinum(o) compounds and their dependence on the geometry of the complex

Abstract

The -Pt N M R parameters of wed phqkms-pIathun(0) cbmplexes &,R(O), L = p k p h h e or phospite, n = 2, 3, 41 have meW mveatimted to flustrate the partieolar N M R propetties of a spin-; bearg metal mud-and for eluddalha of their dependence on the geometry of the complexes. h these compounds the TI values vary as a h & n QE the coordiaation number, n, over severall ordem of magnitude and. therefore, can be wed as artnrctare-dependent patarnetem. I n L P t complexes the relaxation rate varies with Boz, and chemical shift anisoiropy (CSA) is the dominant relaxatioa mecbanipm. Zn the Ljpt and LPi complexes spin-mtatiaoo inereasinfly CootnlJntes ta the relaxation. Far the triethglphosphineplatinm complex &) the conhiution of CSA is reduced by 45% at T T and 240K, whereas the tetrahedral trimethylpboRpbine-platinam &) and trietbyl phwpbit@athum &) complexm relax mainly hy spin-mtation even at 9.4T.

Phosphazenyl Phosphines: The Most Electron‐Rich Uncharged Phosphorus Brønsted and Lewis Bases

“…Theh eteroleptic bisphosphine Pt 0 complexes 17 and 18 were achieved either with Pt 0 or Pt II precursors (Scheme 3 bottom). [29,30] This indicates that the much stronger electron-donating PA Pc ompensates for the better p-backbonding PPh 3 ligand in the overall shielding. So far this seems to be one of the largest 1 J PPt reported for PtÀPR 3 complexes.…”

“…[27] to or even above 2008 8,P APs combine steric and electronic properties that are highly valuable for the design of extremely electron-rich transition-metal bases. [29] The 195 Pt NMR shift of 17 (d = À6238 ppm) is in the range of homoleptic [Pt(PtBu 3 )] (d Pt = À6471 ppm, 1 J PPt = 4420 Hz, Pt À P2 .249 ). In the latter case,the reducing power of PA Ps leads to reductive elimination of [PAPÀCl]Cl and substitution of PPh 3 at [(Ph 3 P) 2 PtCl 2 ]t of orm linear 14-valence-electron bisphosphine complexes.XRD data of 17 reveal that the Pt À P bond to the sterically less demanding PPh 3 ligand (2.213 )is shorter than that to PA P(2.312 ), indicating the importance of PPh 3 p-backbonding in contrast to the extreme PA P sdonation in such heteroleptic model complexes.T he assumption of an almost pure and strong PA P À Pt s-bond is in agreement with results from 31 Pa nd 195 Pt NMR spectroscopy: [28,29] The 1 J PPt Pt À PPh 3 coupling constant of 3236 Hz is only about half as large as that of PtÀPA P( 6153 Hz).…”

NMR and parity nonconservation. Experimental requirements to observe a difference between enantiomer signals

“…From values reported in the literature, the change of is on the order of n × 10 −2 ppm.K −1 . [26][27][28][29] Thus, one may easily calculate the maximum temperature difference ⌬T which will give a 10 mHz linewidth. For spectra recorded at Table 3.…”

Phosphazenylphosphine: Die elektronenreichsten ungeladenen Brønsted‐ und Lewis‐Phosphor‐Basen

“…Die Annahme einer reinen und starken PA P-Pt-s-Bindung wird durch die Ergebnisse aus 31 P-und 195 Pt-NMR-Spektroskopie gestützt:[28,29] Die 1 J PPt -Kopplungskonstante zwischen Metallzentrum und PPh 3 -Ligand ist mit 3236 Hz nur halb so groß wie die Pt-PAP-Kopplung (6153 Hz), die zu den grçßten literaturbekannten 1 J PPt -Kopplungskonstanten gehçrt [29]. Schema 3,unten).…”