Proton-induced dimerisation and related reactions of mononuclear tungsten carbyne complexes. Crystal structures of the compounds [W{C(H)(C6H4Me-4)}(I)(CO)2(η-C5H5)] and [W{η2-C2(OH)(C6H4Me-4)}(CO)(PMe3)(η-C5H5)] [BF4]· (Me2CO)

Abstract Protonation of the compounds [W( 6;CR)(CO) 2 (η-C 5 H 5 )] R = C 6 H 4 Me-4 or Me) with ca. 0.5 mol equivalents of the reagent HBF 4 ·Et 2 O affords the ditungsten salts [W 2 (η-H)(η-RC 2 R)(CO) 4 (η-C 5 H 5 ) 2 ] [BF 4 ] formed via a coupling of the carbyne groups in the precursors. These compounds are readily deprotonated to give the bridged alkyne complexes [W 2 (η-RC 2 R)(CO) 4 (η-C 5 H 5 ) 2 ], a process which is reversed with acid. Aqueous HI with [W( CR)(CO) 2 (η-C 5 H 5 )] affords the iodo carbene complexes [W( CHR)(I)(CO) 2 (η-C 5 H 5 )]. The structure of the species with R = C 6 H 4 Me-4 has been established by X-ray diffraction [W C 2.05(2)A]. The tolyl substituent on the alkylidene carbon atom is transoid to the ηC 5 H 5 ligand, and the alkylidene group is transoid to the iodine atom. Protonation of the ketenyl-tungsten complexes (R = C 6 H 4 Me-4, PR′ 3 = PMe 3 , PPr 3 i or PMePh 2 ; R = Me, PR′ 3 = PMe 3 ) affords the salts [W{η 2 C 2 (OH)(R)}(CO)(PR′ 3 )(η-C 5 H 5 )][BF 4 ] containing hydroxy-alkyne ligands. The structure of the species with R = C 6 H 4 Me-4 and PR′ 3 - PMe 3 has been established by X-ray diffraction. It contains an acetone molecule of crystallisation which is hydrogen bonded to the proton of the hydroxyl group on the alkyne. The 1 H and 13 C-{ 1 H} NMR spectra of the new compounds are reported and discussed.