Isomeric Forms of Heavier Main Group Hydrides:  Experimental and Theoretical Studies of the [Sn(Ar)H]₂ (Ar = Terphenyl) System

Abstract

A series of symmetric divalent Sn(II) hydrides of the general form [(4-X-Ar')Sn(mu-H)]2 (4-X-Ar' = C6H2-4-X-2,6-(C6H3-2,6-iPr2)2; X = H, MeO, tBu, and SiMe3; 2, 6, 10, and 14), along with the more hindered asymmetric tin hydride (3,5-iPr2-Ar*)SnSn(H)2(3,5-iPr2-Ar*) (16) (3,5-iPr2-Ar* = 3,5-iPr2-C6H-2,6-(C6H2-2,4,6-iPr3)2), have been isolated and characterized. They were prepared either by direct reduction of the corresponding aryltin(II) chloride precursors, ArSnCl, with LiBH4 or iBu2AlH (DIBAL), or via a transmetallation reaction between an aryltin(II) amide, ArSnNMe2, and BH3.THF. Compounds 2, 6, 10, and 14 were obtained as orange solids and have centrosymmetric dimeric structures in the solid state with long Sn...Sn separations of 3.05 to 3.13 A. The more hindered tin(II) hydride 16 crystallized as a deep-blue solid with an unusual, formally mixed-valent structure wherein a long Sn-Sn bond is present [Sn-Sn = 2.9157(10) A] and two hydrogen atoms are bound to one of the tin atoms. The Sn-H hydrogen atoms in 16 could not be located by X-ray crystallography, but complementary Mössbauer studies established the presence of divalent and tetravalent tin centers in 16. Spectroscopic studies (IR, UV-vis, and NMR) show that, in solution, compounds 2, 6, 10, and 14 are predominantly dimeric with Sn-H-Sn bridges. In contrast, the more hindered hydrides 16 and previously reported (Ar*SnH)2 (17) (Ar* = C6H3-2,6-(C6H2-2,4,6-iPr3)2) adopt primarily the unsymmetric structure ArSnSn(H)2Ar in solution. Detailed theoretical calculations have been performed which include calculated UV-vis and IR spectra of various possible isomers of the reported hydrides and relevant model species. These showed that increased steric hindrance favors the asymmetric form ArSnSn(H)2Ar relative to the centrosymmetric isomer [ArSn(mu-H)]2 as a result of the widening of the interligand angles at tin, which lowers steric repulsion between the terphenyl ligands.

Iron and tin atom dynamics and hyperfine interactions of two structurally related half-sandwich complexes bearing a distannyl moiety

“…In principle, the normal oxidation states of Sn are characterized by IS values of 0 to w2.22 for Sn(IV), 2.56 to w4.55 for Sn(II), and w2.0 to w2.56 for Sn(0), all in mm s À1 [8]. In a previous study [9] an IS of 1.370(4) was ascribed to Sn(III) in the compound 3,5 iPr 2 -Ar * SnSn(H 2 )-3,5-iPr 2 -Ar * with an Sn(I) site associated with an IS of 3.252(7) mm s À1 all at 90 K. However, the two tin sites in 2 of the present study differ very significantly from those in the Power et al compound 16 [9], including an SneFe ligation in one case and an SneCl ligation in the other, so that no meaningful comparison between the two cases can be made on the basis of presently available data.…”

The Borane Complexes Htbo·BH3 and Htbn·BH3 (Htbo = 1,4,6‐Triazabicyclo[3.3.0]oct‐4‐ene, Htbn = 1,5,7‐Triazabicyclo[4.3.0]non‐6‐ene): Synthesis and Dehydrogenation to Dinuclear Boron Hydrides

“…Distanynes were also shown to add H 2 , [5] and the structure of the product is governed by the size of the ligands. [6] Very recently [GaArЈ] 2 (ArЈ = 2,6-(2,6-iPr 2 C 6 H 3 ) 2 C 6 H 3 ) was treated with H 2 at room temp. and 1 bar to give [ArЈGa(µ-H)H] 2 .…”

Reactions of heavier main‐group compounds with hydrogen, ammonia, ethylene and related small molecules

“…In a more detailed investigation74 we showed that the tin hydride products could also be synthesized by reduction of aryl tin halide precursors with a variety of reducing agents. Calculations on the various hydride products showed that they had similar stability but that as the bulk of the substituents increases (, , cf.…”