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A good entry to highly substituted phenylcarbyne complexes of tungsten containing tert-butyl-isonitrile ligands is provided via Br(CO) 2 (pic) 2 W≡CC 6 H 5  (1) (pic: γ-picoline). The first step includes the replacement of the picoline ligands in 1 by t-BuNC in refluxing CH 2 Cl 2  to give Br(CO) 2 (t-BuNC) 2  W≡CC 6 H 5  (2) in high yield. Complex 2 is then transformed with excess t-BuNC in toluene at 90°C to the carbonyl free carbyne complex trans-Br(t-BuNC) 4 W≡CC 6 H 5  (3). The monocarbonyl substituted analogue of 3, Br(CO)(t-BuNC) 3 W≡CC 6 H 5  (4), is observed by IR spectroscopy as an intermediate of this reaction. Its preparation is achieved by the CoCl 2  catalyzed decarbonylation of 2 in the presence of one equivalent of t-BuNC. trans-Br(t-BuNC) 4 W≡CC 6 H 5  (3) and the analogous iodocompound trans-I(t-BuNC) 4 W≡CC 6 H 5  (5) react with HX (X = Br, I) to give respectively, Br 2 (t-BuNC) 3 W[(t-Bu)HN—C≡C—C 6 H 5 ] (6) and I 2 (t-BuNC) 3 W[(t-Bu)HN—C≡C—C 6 H 5 ] (7) in high yield. Complexes 6 and 7 contain a 4e-donor acetylene ligand resulting from the proton induced coupling of one tert-butylisonitrile with the phenylcarbyne ligand at the tungsten center. The reaction of complex 4 with HBr leads also to the coupling product Br 2 (CO)(t-BuNC) 2 W[(t-Bu)HN—C≡C—C 6 H 5 ] (8), the carbonyl containing analogue of 6, in low yield. With one equivalent of t-BuNC and TlPF 6  compounds 6 and 7 are converted to the cationic complexes [Br(t-BuNC) 4 W[(t-Bu)HN—C≡C—C 6 H 5 ]] + PF 6  -  (9) and [I(t-BuNC) 4 W[(t-Bu)HN—C≡C—C 6 H 5 ]] + PF 6  -  (10) respectively. The analogous chloro compound [Cl(t-BuNC) 4 W[(t-Bu)HN—C≡C—C 6 H 5 ]] + PF 6 - (11) is obtained by halogen exchange from 10 and PPN+Cl - . The composition and structure of the new complexes 3, 4, and 6—11 have been determined by elemental analyses, IR,  1 H NMR,  13 C NMR and mass spectra.

zeitschrift für naturforschung b

Proton-induzierte Kopplung eines tert-Butylisonitril-mit einem Phenylcarbin-Liganden am Wolfram / Proton-Induced Coupling of one tert-Butylisonitrile with one Phenylcarbyne Ligand at Tungsten