Synthesis and Characterization of Tungsten Alkenyl−Carbyne Complexes [(dppe)(CO)2LW⋮CCHCCH2(CH2)nCH2CH2][BF4] (L = CO, MeCN, PMe3) and [(dppe)(CO)2XW⋮CCHCCH2(CH2)nCH2CH2] (X = Cl, Br, I). X-ray Crystal Structure of [(dppe)(CO)2ClW⋮CCHCCH2CH2CH2CH2] and 183W NMR Studies

Alkenyl−vinylidene complexes mer- [(dppe)(CO) 3 W C CHC CH(CH 2 ) n CH 2 CH 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)(CO) 3 W(Me 2 CO)] with 1-ethynylcyclopentanol, 1-ethynylcycloheptanol, and 1-ethynylcyclooctanol. Protonation at the C δ of the alkenyl−vinylidene moiety with HBF 4 ·OEt 2 in diethyl ether or THF leads to the formation of cationic alkenyl−carbyne complexes mer- [(dppe)(CO) 3 W⋮CCH CCH 2 (CH 2 ) n CH 2 CH 2 ][BF 4 ] ( n = 1 ( 2a ), n = 3 ( 2c ), n = 4 ( 2d )). When the protonation is carried out in CH 2 Cl 2, isomeric carbyne complexes mer -[(dppe)(CO) 3 W⋮CCH 2 C CH(CH 2 ) n CH 2 CH 2 ][BF 4 ] ( 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 CCH 2 (CH 2 ) n CH 2 CH 2 ][BF 4 ] (L = CH 3 CN, 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 CCH 2 (CH 2 ) n CH 2 CH 2 ] (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) Å] trans to the alkenyl−carbyne group [W⋮C = 1.830(3) Å]. IR and 1 H, 31 P, 13 C, and 183 W 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 ( 31 P− 183 W) values. The low values for the alkenyl−carbyne groups are among the lowest ever reported, indicating a high trans influence of the carbyne group. 183 W chemical shifts of compounds 1a − 7a were obtained through two-dimensional indirect 31 P, 183 W recording techniques. A down field shifting of 183 W resonances with decreasing π-acceptor ability of the ligands in complexes 2a − 7a was observed.