Synthesis and reactions of cycloheptadienyl and cyclooctadienyl tungsten complexes: X-ray crystal structure of [W(CO) 2(PPh 3) 2(η 5-C 7H 9)][BF 4

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Protonation of the cycloheptatriene complex [W(CO) 3(η 6-C 7H 8)] with H[BF 4] · Et 2O in CH 2Cl 2 affords the cycloheptadienyl system [W(CO) 3(η 5-C 7H 9)][BF 4] ( 1). Complex 1 reacts with NaI to yield [WI(CO) 3(η 5-C 7H 9)], which is a precursor to [W(CO) 2(NCMe) 3(η 3-C 7H 9)][BF 4], albeit in very low yield. The dicarbonyl derivatives [W(CO) 2L 2(η 5-C 7H 9)] + (L 2=2PPh 3, 4, or dppm, 5) were obtained, respectively, by H[BF 4] · Et 2O protonation of [W(CO) 2(PPh 3)(η 6-C 7H 8)] in the presence of PPh 3 and reaction of 1 with dppm. The X-ray crystal structure of 4 (as a 1/2 CH 2Cl 2 solvate) reveals that the two PPh 3 ligands are mutually trans and are located beneath the central dienyl carbon and the centre of the edge bridge. The first examples of cyclooctadienyl tungsten complexes [WBr(CO) 2(NCMe) 2(1–3-η:5,6-C 8H 11)] ( 6) and [WBr(CO) 2(NCMe) 2(1–3-η:4,5-C 8H 11)] ( 7) were synthesised by reaction of [W(CO) 3(NCR) 3] (R=Me or Pr n ) with 3-Br-1,5-cod/6-Br-1,4-cod or 5-Br-1,3-cod/3-Br-1,4-cod (cod=cyclooctadiene), respectively. Complexes 6 and 7 are precursors to the pentahapto-bonded cyclooctadienyl tungsten species [W(CO) 2(dppm)(1–3:5,6-η-C 8H 11)][BF 4] and [W(CO) 2(dppe)(1–5-η-C 8H 11)][BF 4] · CH 2Cl 2.