A combination catalyst of Pd(dba) 2 -PPh 3 -CuI-LiCl or Pd(dba) 2 -P(2-furyl) 3 -CuI-LiCl effectively catalyzed the cross-coupling of (Z)-germyl(stannyl)ethenes with aryl halides, providing novel triethyl(2,2-diarylethenyl)germanes in good to high yields. The reaction proceeds with retention of configuration. Cross-coupling results in the formation of phenylene or phenyleneethynylene derivatives with terminal stereochemically defined vinylgermane unit(s).

Organic compounds possessing a high degree of conjugation, such as poly(phenyleneethynylene)s, have been recognized as ideal materials for advanced electronic and photonic applications such as for organic LEDs, liquid-crystal displays and solar cells.1 In aiming to obtain such functional materials, we have been undertaking a series of studies to synthesize a family of novel low-molecular-weight phenyleneethynylenes with terminal vinylsilane units. Although various phenyleneethynylenes have been synthesized, only a few phenyleneethynylenes with terminal vinylsilane unit(s) have been synthesized so far. Recently, we successfully synthesized the title compound (Fig. 1) by the Sonogashira-Hagihara cross-coupling of 1,4-diethynylbenzene with 2 equiv. of (Z)-1-(4-iodophenyl)-2-(trimethylsilyl)-1-phenylethene, being prepared by the MigitaKosugi-Stille cross-coupling of 1,4-di-iodobenzene with (Z)-1-(tributylstannyl)-2-(trimethylsilyl)-1-phenylethene, 2 in an isolated yield of 89%. An X-ray analysis was undertaken in order to disclose the inherent three-dimensional structure of this novel compound.Single crystals were obtained from an ethyl acetate-hexane solution. A colorless platelet crystal with a size of 0.50 ¥ 0.50 ¥ 0.10 mm was mounted on a glass fiber and used for data collection. The structure was solved by direct methods, and non-H atoms were refined by a full-matrix least-squares method with anisotropic temperature factors. The positions of all Hatoms were located by a difference Fourier synthesis and refined by the riding model. In the final refinement, however, the atomic parameters of the H-atoms were fixed. The molecule has a center of symmetry. The crystal and experimental data are

The crystal of the title compound, C38H38Si2, belongs to space group P1 with cell dimensions of a = 8.6324(6), b = 6.8543(5), c = 27.610(2)Å, a = 89.982(4), b = 89.783(4), and g = 89.990(5)˚. The final R value is 0.057. The central 1,4diphenylbuta-1,3-diyne moiety takes a linear and planar structure. The trimethylsilyl and the terminal phenyl groups are located on opposite sides with respect to the central planar part.