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)CH2CH 2] (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)(C O)(3)W(Me(2)CO)(3) with 1-ethynylcyclopentanol, and 1-ethynylcyclohept anol, and 1-ethynylcyclooctanol. Protonation at the C-delta of the alk enyl-vinylidene moiety with HBF4 . OEt(2) in diethyl ether or THF lead s to the formation of cationic alkenyl-carbyne complexes mer-[(dppe)(C O)(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 comp lexes [(dppe)(CO)(3)W=CCH2C=CH(CH2)(n),CH2CH2][BF4](2a', 2c', 2d') are also generated. The alkenyl-carbyne complexes undergo carbonyl substi tution by donor ligands to give dicarbonyl derivatives of the followin g 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 (4 a), n = 4 (4d)) and (b) neutral complexes trans-[(dppe)(CO)(2)XW=CCH=C CH2(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 diffractio n methods. The W atom displays a distorted octahedral coordination wit h 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 corr esponding (1)J(P-31-W-183) values. The low values for the alkenyl-carb yne 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 recordi ng techniques. A down field shifting of W-183 resonances with decreasi ng pi-acceptor ability of the ligands in complexes 2a-7a was observed.