Imido alkylidene bispyrrolyl complexes of tungsten

We have prepared tungsten bispyrrolyl (Pyr) or bis-2,5-dimethylpyrrolyl (Me(2)Pyr) complexes W(NAr)-(CHCMe2Ph)(2)(eta(1)-Pyr)(2)(DME) (1), W(NAr)(CHCMe2Ph)(eta(1)-Me(2)Pyr)(eta 5-Me(2)Pyr) (2), W(NArCl)(CHCMe3)-(eta(1)-Pyr)(2)(DME) (3b), and W(NArCl)(CHCMe3)(eta(1)-Me(2)Pyr)(eta(5)-Me(2)Pyr) (4) (Ar = 2,6-diisopropylphenyl, Ar-cl = 2,6-dichlorophenyl) in excellent yields by treating the appropriate W(NR)(CHCMe2R')(OTf)(2)-(DME) species with LiPyr or LiMe(2)Pyr. Compounds 2 and 4 react with ethylene slowly to yield stable methylene complexes, W(NAr)(CH2)(eta(1)-Me(2)Pyr)(q'-Me2Pyr) (5) and W(NArCl)(CH2)(eta(1)-Me(2)Pyr)(eta(5)- (6). In contrast, treatment of what is believed to be a fortuitous 1:1 mixture of 3b and [W(NArCl)(CHCMe3)(eta(1)-Pyr)(2)][W(NArCl)(CHCMe3)(eta(1)-Pyr)(eta(5)-Pyr)] with ethylene leads to formation of [W(mu-NArCl)(eta(1)-Pyr)(2)](2) (7) in moderate (54%) yield. Compounds 2 and 4 react with [HNMe2Ph]-[B(Ar-F)(4)] (Ar-F = 3,5-(CF3)(2)C6H3) in dichloromethane to yield cationic species that contain one eta(5)-Me(2)Pyr ligand and one 2,5-dimethylpyrrolenine ligand formed through addition of a proton to C(2) of a dimethylpyrrolyl ligand, e.g., [W(NArCl)(CHCMe3)(Me(2)Pyr){NC4(H-3-2,3,4)(Me-2-2,5)}](+)[B(Ar-F)(4)](-) (9). X-ray studies were carried out on 1, 2, 6, 7, and 9.