Relativistic DFT Calculation of ¹¹⁹Sn Chemical Shifts and Coupling Constants in Tin Compounds

Abstract

The nuclear shielding and spin-spin coupling constants of (119)Sn in stannane, tetramethylstannane, methyltin halides Me4-nSnXn (X = Cl, Br, I; n = 1-3), tin halides, and some stannyl cations have been investigated computationally by DFT methods and Slater all-electron basis sets, including relativistic effects by means of the zeroth order regular approximation (ZORA) method up to spin-orbit coupling. Calculated (119)Sn chemical shifts generally correlate well with experimental values, except when several heavy halogen atoms, especially iodine, are bound to tin. In such cases, calculated chemical shifts are almost constant at the scalar (spin-free) ZORA level; only at the spin-orbit level is a good correlation, which holds for all compounds examined, attained. A remarkable "heavy-atom effect", analogous to that observed for analogous alkyl halides, is evident. The chemical shift of the putative stannyl cation (SnH3(+)) has also been examined, and it is concluded that the spectrum of the species obtained in superacids is inconsistent with a simple SnH3(+) structure; strong coordination to even weak nucleophiles such as FSO3H leads to a very satisfactory agreement. On the contrary, the calculated (119)Sn chemical shift of the trimesitylstannyl cation is in very good agreement with the experimental value. Coupling constants between (119)Sn and halogen nuclei are also well-modeled in general (taking into account the large uncertainties in the experimental values); relativistic spin-orbit effects are again quite evident. Couplings to (13)C and (1)H also fall, on the average, on the same correlation line, but individual values show a significant deviation from the expected unit slope.

Relativistic and Electron-Correlation Effects on the Nuclear Magnetic Resonance Shieldings of Molecules Containing Tin and Lead Atoms

“…Some of them were proposed based on theoretical calculations [7][8][9][10][11][12][13] and others based on a mixture between spin-rotation measurements and theoretical calculations of free atoms.…”

Karplus‐Type Dependence of Vicinal 119Sn‐13C and 119Sn‐1H Spin‐Spin Couplings in Organotin(IV) Derivatives: A DFT Study

“…Chemical shifts can be accurately predicted even at the nonrelativistic level due to error compensation in the calculated shielding constants, [24][25][26][27][28] provided no other heavy atoms are bound to tin. [29,30] Regarding the calculation of the coupling constants it has been shown that even for moderately heavy nuclei scalar relativistic effects are not negligible. [31,32] In this context relativistic ZORA DFT calculation of n J( 119 Sn,X) (n = 1,2; X = 1 H, 13 C) have been reported [29,33,34] [35] allowed to correlate these couplings with the θ angle of the dimethylti-n(IV) moiety even in those cases where the aforementioned Lockhart-Manders equations fail.…”

“…[29,30] Regarding the calculation of the coupling constants it has been shown that even for moderately heavy nuclei scalar relativistic effects are not negligible. [31,32] In this context relativistic ZORA DFT calculation of n J( 119 Sn,X) (n = 1,2; X = 1 H, 13 C) have been reported [29,33,34] [35] allowed to correlate these couplings with the θ angle of the dimethylti-n(IV) moiety even in those cases where the aforementioned Lockhart-Manders equations fail. [12] Again, a systematic error compensation might be at the root of the observed good agreement.…”

Covalent Bonds in α‐SnF2 Monitored by J‐Couplings in Solid‐State NMR Spectra

“…Wiley-VCH ZAAC 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 The shortest distances for heteronuclear and homonuclear pairs of nuclei reported for the X-ray structure [1] As a third contribution to line broadening, J-couplings have to be taken into account for 119 Sn, since it has been documented previously [9][10][11][12][13][14][15][16][17][18][19][20][21] that they may also be of the order of kHz. In fact, the J-couplings for 119 Sn can be so large that it has been possible to determine the anisotropy of this interaction in some organo-tin compounds [14] by using off-magic angle spinning.…”

“…Unlike dipolar couplings, which act through space, J-couplings are mediated by covalent bonds, and are difficult to observe in solid-state NMR, because they are usually much smaller than dipolar couplings [6][7][8]. For 119 Sn however, J-couplings tend to be comparatively large (in the range of kHz), and have been reported before in the literature for a variety of compounds [9][10][11][12][13][14][15][16][17][18][19][20][21]. The existence of J-couplings in α-SnF 2 shown here is further evidence for the existence of covalent Sn-F bonds in tin(II) fluoride.…”