Synthesis and characterization of tungsten alkenyl-carbyne complexes [(dppe)(CO)(2)LW CCH=CCH2(CH2)(n)CH2CH2][BF4] (L=CO, MeCN, PMe(3)) and [(dppe)(CO)(2)XW CCH=CCH2(CH2)(n)CH2CH2] (X=Cl, Br, I). X-ray crystal structure of [(dppe)(CO)(2)ClW CCH=CCH2CH2CH2CH2] and W-183 WMR studies

Alkenyl-vinylidene complexes mer-[(dppe)(CO)(3)W=C=CHC=CH(CH2)(n)CH2CH2] (dppe = 1,2-bis(diphenylphosphino)ethane; n = 1 (1a), n = 3 (1c), n = 4 (1d)) have been prepared by reaction of the complex fac-[(dppe)(CO)(3)W(Me(2)CO)(3) with 1-ethynylcyclopentanol, and 1-ethynylcycloheptanol, and 1-ethynylcyclooctanol. Protonation at the C-delta of the alkenyl-vinylidene moiety with HBF4 . OEt(2) in diethyl ether or THF leads to the formation of cationic alkenyl-carbyne complexes mer-[(dppe)(CO)(3)W=CCH=CCH2(CH2)(n)CH2CH2][BF4](n = 1(2a), n = 3 (2c), n = 4 (2d)). When the protonation is carried out in CH2Cl2, isomeric carbyne complexes mer-[(dppe)(CO)(3)W=CCH2C=CH(CH2)(n),CH2CH2][BF4](2a', 2c', 2d') are also generated. The alkenyl-carbyne complexes undergo carbonyl substitution by donor ligands to give dicarbonyl derivatives of the following types: (a) cationic complexes trans-[(dppe)(CO)(2)LW= CCH=CCH2(CH2)(n)CH2CH2][BF4] (L = CH3CN, n = 1(3a), n = 4 (3d); L = PMe(3), n = 1 (4a), n = 4 (4d)) and (b) neutral complexes trans-[(dppe)(CO)(2)XW=CCH=CCH2(CH2)(n)CH2 (X = Cl, n = 1 (5a), n = 2 (5b), n = 3 (5c), n = 4 (5d); X = Br, n = 1 (6a), n = 4 (6d); X = I, n = 1 (7a), n = 3 (7c), n = 4 (7d)). The structure of complex 5a was determined by X-ray diffraction methods. The W atom displays a distorted octahedral coordination with the Cl atom [W-Cl = 2.540(1) Angstrom] trans to the alkenyl-carbyne group [W=C = 1.830(3) Angstrom]. IR and H-1, P-31, C-13, and W-183 NMR data are reported. The sequence for the trans influence in the order alkenyl-carbyne > alkenyl-vinylidene > CO could be found from the corresponding (1)J(P-31-W-183) values. The low values for the alkenyl-carbyne groups are among the lowest ever reported, indicating a high trans influence of the carbyne group. W-183 chemical shifts of compounds 1a-7a were obtained through two-dimensional indirect P-31, W-183 recording techniques. A down field shifting of W-183 resonances with decreasing pi-acceptor ability of the ligands in complexes 2a-7a was observed.