Pd-catalysed reactions of alkynes with model distannanes and poly[di-(n-butyl)]stannane.

A reinvestigation of Pd-catalysed alkyne (R'-C≡CH; R' = H, Ph) insertion chemistry involving R(3)SnSnR(3) (3a: R = Me; 3b: R = n-Bu) was undertaken. Model distannyl ethylenes 4a-b (Me(3)SnCH=CR'SnMe(3)) and 5a-b ((n-Bu)(3)SnCH=CR'Sn(n-Bu)(3)) were reproduced and further characterized by NMR ((119)Sn, (13)C, (1)H) and UV-Vis spectroscopy. In the presence of an excess of phenylacetylene, dimerization-carbostannylation of compound 4b yielded the new conjugated butadiene, (Z,Z)-1,4-bis(trimethylstannyl)-1,4-diphenyl-buta-1,3-diene (9). An X-ray structure determination of 9 reveals a symmetrical double-bond Z confirmation. Compound 9 was further characterized by NMR, UV-Vis spectroscopy, and MS. A DFT analysis of model compounds (4a-b, 5a-b, 9) and the experimental and theoretical λ(max) values from the UV-Vis spectra were also compared. Acetylene and phenylacetylene Pd-catalysed insertion into the backbone of poly[di-(n-butyl)]stannane 12 resulted in new, modest molecular weight, partially inserted alkene tin polymers (13a-b) that were also characterized by GPC, NMR, UV-Vis spectroscopy and elemental analysis.