Cyclopentadienyldichlorotitanum(III): A Free-Radical-like REagent for Reducing -N=N- Multiple Bonds in Azo and Diazo Compounds

Article abstract of DOI:10.1021/ja00363a015

Diphenyldiazomethane was reduced by (co = η⁵-C5H5) to a hydrazonido(2-) ligand to form <(cpTiCl2)2(μ-Ph2C=NN)>, which loses and evolves to a dinuclear complex, <(cpTiCl)2(μ-Ph2C=NN)>, in which the two (cpTiCl) units are bridged by two hydrazonido(2-) ligands.Both hydrazonido ligands are η²-N,N' bonded to the same titanum atom in the solid state, with titanum-nitrogen bond distances ranging from 2.006(6) to 2.178(5) Angstroem, while the second titanum is bonded at very short distances to the terminal nitrogens only, 1.860(5) and 1.835(6) Angstroem.The 1H NMR spectrum at -64 deg C (CDCl3) is in agreement with the solid-state structure showing the nonequivalence of the two cp rings, which become equivalent at room temperature because of the stereochemical nonrigidity of the hydrazonido ligand. reacted with azobentene, forming a dimeric complex, <(cpTiCl)2(μ-PhN)(μ-Ph2N2)>, in which the phenylimido ligand forms from a -N=N- bend cleavage promoted by titanum(III).Phenylimido bridges the two titanum atoms at rather short distance Ti-N, 1.920(4) Angstroem, with nitrogen having sp² geometry, so that a multiple Ti-N interaction is involved.The molecular complexity of , which may be a main point in determining its reactivity, was determined by X-ray analysis carried out on the solid isolated from THF solution, .It was found to be formed by the same number of pentacoordinate and tetracoordinate titanum(III) monomeric units.Crystallographic details for are as follows: space group P1/ (triclinic), a = 11.139(4), b = 13.641(5), c = 9.398(4) Angstroem, α = 95.31(3), β = 106.94(2), γ = 98.51(3) deg, V = 1337.0(9) Angstroem³, D_calc = 1.451 g cm^-3, Z = 2.The final R factor is 4.9percent for 2727 observed reflections.Crystallographic details for <(cpTiCl)2(μ-Ph2C=NN)2> are as follows: space group P2₁/c (monoclinic), a = 18.704(2), b = 785(1), c = 21.049(2) Angstroem, β = 100.57(1) deg, V = 3400.0(6) Angstroem³, D_calc = 1.339 g cm^-3, Z = 4.The final R factor is 5.4percent for 2519 observed reflections.Crystallographic details for <(cpTiCl)2(μ-PhN)(μ-Ph2N2)> are as follows: space group C2/c (monoclinic), a = 14.041(2), b = 12.743(2), c = 15.875(3) Angstroem, β = 115.23(32) deg, V = 2569.5(8) Angstroem³, D_calc = 1,474 g cm^-3, Z = 4.The final R factor is 3.1percent for 1035 observed reflections.