Synthesis and Reactivity of Titanium Hydrazido Complexes Supported by Diamido-Ether Ligands

The synthesis and reactivity of titanium
diphenyl hydrazido(2−) complexes supported by the diamido-ether
ligands O­(2-C6H4NSiMe3)2 (N2ArO) and O­(CH2CH2NSiMe3)2 (N2O) are described. Reaction
of Li2N2ArO or Li2N2O with Ti­(NNPh2)­Cl2(py)3 afforded
Ti­(N2ArO)­(NNPh2)­(py)2 (14) or Ti­(N2O)­(NNPh2)­(py)2 (15) with κ3-mer-bound
diamido-ether ligands. Reaction with tBu-bipy (4,4′-di-tert-butyl-2,2′-bipyridyl) or bipy (2,2′-bipyridyl)
gave a switch to κ3-fac-coordination.
Reaction of 15 with Ar′NCO (Ar′ = 2,6-C6H3iPr2) gave Ti­{O­(CH2CH2NSiMe3)­(CH2CH2NC­(O)­N­(SiMe3)­Ar′)}-{N­(NPh2)­C­(O)­N­(Ar′)},
in which the substrate has inserted into a Ti–Namide bond of N2O as well as adding to the TiNα multiple bond. With Ar′NCS the [2+2] cycloaddition
product Ti­(N2O)­{N­(NPh2)­C­(NAr′)­S}­(py)
was obtained, and with Ar′NCSe a mixture was formed including
Ti2(N2O)2(μ-Se)2. Both 14 and 15 reacted with ArFxCN (ArFx = C6H3F2 or
C6F5) to give TiNα bond
insertion products of the type Ti­(L)­{NC­(ArFx)­NNPh2}­(py)2 (L = N2ArO or N2O) containing hydrazonamide ligands. Reaction of 14 with
XylNC (Xyl = 2,6-C6H3Me2) gave only
the isonitrile σ-adduct Ti­(N2ArO)­(NNPh2)­(py)­(CNXyl), whereas 15 underwent Nα–Nβ bond reductive cleavage with tBuNC or XylNC forming Ti­(N2O)­(NPh2)­(NCNtBu) or Ti­{O­(CH2CH2NSiMe3)­(CH2CH2NCN­(SiMe3)­Xyl)}­(NPh2)­(NCNXyl) (27). Both contain metalated carbodiimide
ligands, but in 27 an additional reaction of XylNC with
the Ti–Namide bond of N2O has taken place.
Compound 15 also reacted with a number of internal alkynes
RCCR′ (R = R′ = Me or Ph; R = Me, R′ = aryl)
to give Nα–Nβ bond reductive
cleavage products of the type Ti­{O­(CH2CH2NSiMe3)­(CH2CH2NC­(R)­C­(R′)­NSiMe3}­(NPh2), again involving a reaction of a Ti–Namide bond.