The influence of charge on nuclear magnetic resonance isotope effects

Abstract

. J. Chem. 65, 2707Chem. 65, (1987.Deuterium isotope effects on the 3 '~ shielding constants and spin-spin coupling constants in the isoelectronic series, pH2-, pH3, PH4+, are examined. Also, deuterium isotope effects on the nuclear magnetic resonance parameters of SnH3-are examined and compared with our earlier results on SnH4 and SnH3+. The experimental results are analyzed using the models of Jameson and Osten. In each isoelectronic series it is found that the isotope effects on the heavy atom chemical shifts are largest for the negatively charged ions and essentially zero for the positively charged ions, as predicted by recent molecular orbital calculations.The primary isotope effects on J(A,H) are positive for all species containing lone-pair electrons, otherwise A, 'J(A,H) is negative. The primary and secondary isotope effects on J(Sn,H) in the SnH3-ion are the largest reported to date. RODERICK E. WASYLISHEN et NEIL BURFORD. Can. J. Chem. 65, 2707.On a ttudit les effets isotopiques du deutCrium sur les constantes d'Ccran du 31P et sur les constantes de couplage spin-spin de la strie isoClectronique pH2-, pH3 et Ph4+ : On a aussi ttudiC les effets isotopiques du deuttrium sur les paramktres en resonance magnttique nucltaire du SnH3-et on les a comparCs avec nos rtsultats anttrieurs sur le SnH4 et le SnH3+. On a analyse les rtsultats exptrimentaux en utilisant les modkles de Jameson et Osten. Dans chacune des stries isotlectroniques, on a trouvt que les effets isotopiques sur les dtplacements chimiques de I'atome lourd sont les plus importants pour les ions chargCs nkgativement et essentiellement ztro pour les ions chargts positivement; ces rCsultats sont en accord avec les prkdictions dtrivCes de calculs rtcents d'orbitales moltculaires. Les effets isotopiques primaires sur J (A,H) sont positifs pour toutes les espkces contenant des paires libres dlClectrons; autrement, la valeur de A, 'J(A,H) est ntgative. Les valeurs des effets Clectroniques primaire et secondaire sur J(Sn,H) dans I'ion SnH3-sont les valeurs les plus ClevCes ii 6tre rapporttes a date.[Traduit par la revue]

Deprotonation of Organogermanium and Organotin Trihydrides

“…The 119 Sn NMR signals of salts 5 – 7 lie at higher field (−473 to −497 ppm) in comparison to the starting materials [Ar′SnH 3 ( 2 ) −391.2 ppm, Ar*SnH 3 ( 3 ) −384.7 ppm]. , Comparable trialkyl or triaryl stannates exhibit resonances in a range at lower field (−78 to −274.4 ppm). − Uhlig and co-workers reported on the deprotonation of t Bu 2 SnH 2 with t BuLi and found a signal in the 119 Sn NMR spectrum for the dialkylhydridostannate at −9.7 ppm with a coupling constant of 1 J Sn–H 287 Hz . Deprotonation of stannane SnH 4 in a mixture of liquid ammonia and sodium metal was published by Wasylishen and Burford to give sodium hydridostannate, which exhibits a 119 Sn NMR signal at much higher field (−782.5 ppm with a coupling constant 1 J Sn–H of 108.5 Hz) . The 1 J Sn–H coupling constants of anions 5 , 6 , and 7 lie in the range of 137–248 Hz.…”

“…64 Deprotonation of stannane SnH 4 in a mixture of liquid ammonia and sodium metal was published by Wasylishen and Burford to give sodium hydridostannate, which exhibits a 119 Sn NMR signal at much higher field (−782.5 ppm with a coupling constant 1 J Sn−H of 108.5 Hz). 65 The 1 J Sn−H coupling constants of anions 5, 6, and 7 lie in the range of 137−248 Hz. In comparison, organotin(IV) hydrides like for example Ar*SnH 3 (1934 Hz) and Ar′SnH 3 (1934 Hz) show a much larger 1 J Sn−H coupling constant whereas organotin(II) hydrides and Lewis base adducts thereof exhibit 1 J Sn−H coupling constants around 100 Hz.…”

“…7,26,66 Because the free electron pair of the organodihydrido anion is essentially located in the s-orbital, the influence of the s-orbital on the Sn−H bond is reduced in these deprotonation products, which results in a much smaller coupling constant 1 J Sn−H in comparison to organotin trihydrides. 65 Reactivity studies of the organodihydrido anions of germanium and tin were carried out in reactions with lowvalent Group 14 element electrophiles. The terphenyldihydridogermanium anion of 4 was reacted with low-valent halides of tin and lead (Scheme 2).…”

“…The 1 J Sn–H coupling constants of anions 5 , 6 , and 7 lie in the range of 137–248 Hz. In comparison, organotin­(IV) hydrides like for example Ar*SnH 3 (1934 Hz) and Ar′SnH 3 (1934 Hz) show a much larger 1 J Sn–H coupling constant whereas organotin­(II) hydrides and Lewis base adducts thereof exhibit 1 J Sn–H coupling constants around 100 Hz. ,, Because the free electron pair of the organodihydrido anion is essentially located in the s-orbital, the influence of the s-orbital on the Sn–H bond is reduced in these deprotonation products, which results in a much smaller coupling constant 1 J Sn–H in comparison to organotin trihydrides …”

Synthesis, structure and reactivity of μ3-SnH capped trinuclear nickel cluster

“…Further details of the molecular and electronic structure were elucidated by 31 P, 1 H, and 119 Sn NMR spectroscopy. The 31 P NMR spectroscopy of 2 in benzene-d 6 revealed symmetrical binding of the μ 3 -SnH and μ 3 -H capping groups on the NMR timescale as demonstrated by an isolated sharp singlet resonance at 23.4 ppm.…”