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

Eric Rivard, Roland C. Fischer, Robert Wolf, Yang Peng, W. Alexander Merrill, Nathan D. Schley, Zhongliang Zhu, Lihung Pu, James C. Fettinger, Simon J. Teat, Isreal Nowik, Rolfe H. Herber, Nozomi Takagi, Shigeru Nagase, Philip P. Power

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A series of sym. divalent Sn(II) hydrides of the general form [(4-X-Ar')Sn(μ-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 asym. 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 prepd. either by direct redn. of the corresponding aryltin(II) chloride precursors, ArSnCl, with LiBH4 or iBu2AlH (DIBAL), or via a transmetalation reaction between an aryltin(II) amide, ArSnNMe2, and BH3·THF. Compds. 2, 6, 10, and 14 were obtained as orange solids and have centrosym. dimeric structures in the solid state with long Sn···Sn sepns. of 3.05 to 3.13 Å. The more hindered tin(II) hydride 16 crystd. 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) Å] 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 crystallog., but complementary Moessbauer studies established the presence of divalent and tetravalent tin centers in 16. Spectroscopic studies (IR, UV-vis, and NMR) show that, in soln., compds. 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 unsym. structure ArSnSn(H)2Ar in soln. Detailed theor. calcns. have been performed which include calcd. 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 asym. form ArSnSn(H)2Ar relative to the centrosym. isomer [ArSn(μ-H)]2 as a result of the widening of the interligand angles at tin, which lowers steric repulsion between the terphenyl ligands. [on SciFinder(R)]
Original languageEnglish
Pages (from-to)16197-16208
Number of pages12
JournalJournal of the American Chemical Society
Issue number51
Publication statusPublished - 2007

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