Formation of η1-Iminoacyl Compounds by Insertion of Isonitriles in Pentamethylcyclopentadienyl-Tetramethylfulvene Compounds of Titanium and Zirconium. Intramolecular C-H Activation of a Pentamethylcyclopentadienyl Group To Give a Tridentate Ligand with T

摘要

Cp*FvMCl [Cp* = η5-C5Me5, Fv = η6-C5Me4CH2; M = Ti (1), Zr (2)] react with CN(2,6-Me2C6H3 (CNXyl) to give η1-iminoacyl complexes Cp*[η5:η1-C5Me4CH2C(=NXyl)]MCl [M = Ti (3), Zr (4)] through insertion of the isonitrile into the M-CH2(Fv) bond. Both iminoacyl complexes, 3 and 4, react with free isonitrile to give a second insertion and coupling of two CNXyl molecules with formation of Cp*[η5:η1-C5Me4CH2C(=NXyl)C(=NXyl)]MCl [M = Ti (5), Zr (6)]. The molecular structure of 6 shows a typical bent metallocene geometry around zirconium with two coupled isonitrile fragments attached to a cyclopentadienyl ligand and one of them η1-bonded through the carbon atom to the metal. Compound 6 crystallizes in the monoclinic space group P21/n with a = 12.431 (2) Å, b = 16.820 (5) Å, c = 16.434 (3) Å, β = 102.06 (2)°, V = 3360 (1) Å3, and Z = 4. The Zr-Cl(2.430 (1) Å) and the Zr-C(iminoacy1) [2.336 (2) Å] bonds are located in the equatorial plane between the cyclopentadienyl ligands [Cl-Zr-C 97.68 (6)°]. Compound 5 rearranges thermally through C-H activation of a methyl substituent on a pentamethylcyclopentadienyl ligand and forms a bis(peralkylcyclopentadienyl) titanium vinyl chloride complex [η5:η1:η5-C5Me4CH2C(NHXyl)=CN(Xyl)CH2C5Me4]TiCl (7), in which the cyclopentadienyl ligands are bridged by a C3NC chain. The bridge itself is bonded to titanium through a regular Ti-C bond, connecting the metal with a C=C fragment of the coupled isonitrile molecules. Crystals of 7 are triclinic, space group P1, with a = 8.946 (1) Å, b = 13.499 (3) Å, c = 16.360 (3) Å, (α = 102.91 (1)°, β = 102.81 (1)°, γ = 108.28 (1)°, V = 1735.3 (6) Å3, and Z = 2. The peralkylcyclopentadienyl ligands form a normal bent metallocene, bridged at the front of the wedge by a five-membered chain. The Ti-Cl [2.374 (1) Å] and the Ti-C [2.158 (4) Å] bonds are located in the equatorial plane of the titanocene unit [Cl-Ti-C 97.7 (1)°]. Bridging of the cyclopentadienyl ligands is also found for the zirconium complex 6, but the main product results from a 1,3-hydrogen shift in the side chain to give a cyclopentadienyl-amide bidentate ligand and formation of Cp*[η5:η1-C6Me4CH=C(CH=NXyl)NXyl]ZrCl (8).