Characterization of the Sterically Encumbered Terphenyl-Substituted Species 2,6-Trip₂H₃C₆S̈n−Sn(Me)₂C₆H₃-2,6-Trip₂, an Unsymmetric, Group 14 Element, Methylmethylene, Valence Isomer of an Alkene, Its Related Lithium Derivative 2,6-Trip₂H₃C₆(Me)₂Sn−Sn(Li)(Me)C₆H₃-2,6-Trip₂, and the Monomer Sn(t-Bu)C₆H₃-2,6-Trip₂ (Tri

Abstract

The reaction of the recently reported sterically encumbered terphenyl tin(II) halide species Sn(Cl)C6H3-2,6-Trip2 (Trip = C6H2-2,4,6-i-Pr3), 1, with 1 equiv of MeLi or MeMgBr afforded 2,6-Trip2H3C6Sn-Sn(Me)2C6H3-2,6-Trip2, 2, which is the first stable group 14 element methylmethylene (i.e., CH3CH) analogue of ethylene (H2CCH2). Reaction of 1 with 1.5 equiv of MeLi yielded the stannylstannate species 2,6-Trip2H3C6(Me)2Sn-Sn(Li)(Me)-C6H3-2,6-Trip2, 3, whereas reaction of 1 with 1 equiv of t-BuLi gave the heteroleptic stannanediyl monomer Sn(t-Bu)C6H3-2,6-Trip2 (4). The compounds 2-4 were characterized by 1H, 13C (7Li, 3 only), and 119Sn NMR spectroscopy in solution and by UV-vis spectroscopy. The X-ray crystal structures of 2-4 were also determined. The formation of the stannylstannanediyl 2 instead of the expected symmetrical, valence isomer "distannene" form (Sn(Me)C6H3-2,6-Trip2)2, 6, is explained through the ready formation of LiSn(Me)2C6H3-2,6-Trip2, 5, which reacts rapidly with 1 to produce 2 which can then react with a further equivalent of MeLi to give 3. The stability of singly bonded 2 in relation to the formally doubly bonded 6 was rationalized on the basis of the difference in the strength of their tin-tin bonds. In contrast to the methyl derivatives, the reaction of 1 with t-BuLi proceeded smoothly to give the monomeric compound 4. Apparently, the formation of a t-Bu analogue of 5 was prevented by the more crowding t-Bu group. Compound 2 is also the first example of a stable molecule with bonding between a two-coordinate, bivalent tin and four-coordinate tetravalent tin. Both compounds 2 and 3 display large J 119Sn-119Sn couplings between their tin nuclei and the tin-tin bond lengths in 2 (2.8909(2) A) and 3 (2.8508(4) A) are relatively normal despite the presence of the sterically crowding terphenyl substituents.

The Reactions of Aryl Tin(II) Hydrides {AriPr6Sn(μ-H)}2 (AriPr6 = C6H3-2,6-(C6H2-2,4,6-iPr3)2) and {AriPr4Sn(μ-H)}2 (AriPr4 = C6H3-2,6-(C6H3-2,6-iPr2)2) with Aryl Alkynes: Substituent Dependent Structural Isomers

“…The data for 1 show that the C ipso –Sn–C angle is 98.15(6)°, with a very similar C ipso –Sn–C angle of 98.63(7)° being observed for 2 . The C ipso –Sn bond lengths in 1 and 2 span the narrow range of 2.1994(17)–2.2054(16) Å and are similar to those previously reported by this group and by others (2.168(8)–2.204(8) Å) ,− as well as being close to the sum (2.17 Å) of the single bond radii of carbon (0.77 Å) and tin (1.40 Å) . The C ethenyl –Sn bond lengths are 2.2020(17) Å in 1 and 2.2061(18) Å in 2 .…”

Dynamic Behavior and Isomerization Equilibria of Distannenes Synthesized by Tin Hydride/Olefin Insertions: Characterization of the Elusive Monohydrido Bridged Isomer

“…All 1 H, 13 C­{ 1 H}, and 119 Sn­{ 1 H} NMR spectroscopic data are listed in greater detail in the Supporting Information. The 119 Sn­{ 1 H} NMR spectrum of 2a was recorded at 330 K and displayed a broad resonance at 1908 ppm which lies within the previously reported range for monomeric stannylene species (442–2235 ppm) ,− and is similar to that in the monomer Ar i Pr 6 Sn t Bu at 1904 ppm, indicating that 2a dissociates to the monomer Ar i Pr 6 Sn­(C 2 H 5 ) in solution at room temperature. The 1 H NMR spectrum of 2a was recorded at 330 K in a d 8 -toluene solution.…”

“…They also undergo several facile reactions that include C–H activation and the hydroelementation of small molecules. ,− Roesky and co-workers reported that the monomeric Sn­(II) hydride, [HC­(CMeNAr) 2 ]­SnH (Ar = 2,6- i Pr 2 C 6 H 3 ), could hydrostannylate ketones, CO 2 , and terminal alkynes to give Sn­(II) alkoxides, stannylene formates, and alkenyl stannylenes. − Jones and co-workers used the bulky amido ligand, −N­(Ar † )­(SiPr i 3 ) (Ar † = C 6 H 2 -2,6-{C­(H)­Ph 2 } 2 -4- i Pr), to stabilize a singly bonded digermyne which reacted with H 2 to form monomeric Ar † (SiPr i 3 )­NGeH that catalyzed the hydroboration of carbonyl groups to afford alcohols . In addition, in situ generated Sn­(II) hydrides were shown to catalyze the dehydrocoupling of amines and boranes. , The high reactivity of the group 14 metal hydrides ArEH (E  Ge, Sn) is due to their partially open shell structures which have an occupied s and an empty p-orbital which can interact with the frontier orbitals of unsaturated hydrocarbons and related molecules. , …”

Triphenylene-based tris-N-heterocyclic stannylenes

“…Stannylenes are mostly coloured in hydrocarbon solution due to their symmetry forbidden n-p transition in the visible region. [34][35][36][37][38][39][40][41][42] As shown in Fig. 2, both 2a and 2b feature two broad absorption bands.…”