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 reactions of the aryl tin(II) hydrides {(ArSn)-Sn-iPr6(mu-H)}(2) (Ar-iPr6 = C6H3-2,6-(C6H2-2,4,6-Pr-t(3))(2)) and {(ArSn)-Sn-iPr4(mu-H)}(2) (Ar-iPr4 = C6H3-2,6-(C6H3-2,6-Pr-r(2))(2)) with aryl alkynes were investigated. Reaction of {(ArSn)-Sn-iPr6 (mu-H)}(2) and {(ArSn)-Sn-iPr4(mu-H)}(2) with 2 equiv of diphenyl acetylene, PhCCPh, afforded the aryl alkenyl stannylenes (ArSnC)-Sn-iPr6(Ph)-C(H)Ph (1) and (ArSnC)-Sn-iPr4(Ph)C(H)Ph (2). In contrast, the analogous reactions of {(ArSn)-Sn-ipr6(mu-H)}(2) with 2 equiv of phenyl acetylene, HCCPh, afforded a high yield of the cis-1,2 addition product Ar-iPr6(H)SnC(H)C(Ph)Sn(H)Ar-iPr6 (3), which has a four-membered Sn2C2 core structure comprised of two Sn-Sn bonded Sn(H)Ar-iPr6 units bridged by a -C(H)=C(Ph)- moiety. The corresponding reaction of the less bulky hydride {Ar(iPr4)sn(mu-H)}(2) with 2 equiv of phenyl acetylene leads to (ArSnC)-Sn-iPr4(H)C(Ph)Sn(H)(2)Ar-iPr4 (4) which unlike 3 has no Sn-Sn bonding. Instead, the tin atoms are connected solely by a -C(H)=C(Ph)- moiety. Each tin atom cAriies a Ar-iPr4 substituent but one is also substituted by two hydrogens. The difference in behavior between PhCCPh and HCCPh is attributed mainly to the difference in steric bulk of the two substrates. The different products 3 and 4 are probably a consequence of the difference in size and dispersion force interactions of the Ar-iPr6 and Ar-iPr4 substituents. Compounds 1-4 were characterized by H-1, C-13, and Sn-119 NMR, UV-vis, and IR spectroscopy and structurally by X-ray crystallography.