C−C and C−N Coupling Reactions of an Imidotitanium Complex with Isocyanides

Reaction of the imidotitanium complex [(κ3-N2Npy)Ti(NtBu)(py)] (1) [N2Npy = (2-C5H4N)C(Me)(CH2NSiMe3)2] with 2,6-xylylisocyanide led to double insertion of the isocyanide into the imidotitanium bond and yielded the four-membered titanacycle [(κ3-N2Npy)Ti{N(tBu)C(N-2,6-Me2C6H3)C(N-2,6-C6H3Me2)}] (2), which was characterized by X-ray crystallography. While unreactive toward bulky arylisocyanides, 2 reacted with a whole series of isocyanides R−NC [R = Et, nBu, iPr, Cy, tBu, PhCH2, p-Tol, (R)-CH(CH3)Ph] to give the iminoketene complexes [(κ3-N2Npy)Ti{N(tBu)C[N(2,6-Me2C6H3)]C(CNR)N(2,6-Me2C6H3)](R = Et, 3a; nBu, 3b; iPr, 3c; Cy, 3d; tBu, 3e; PhCH2, 3f; p-Tol, 3g; (R)-CH(CH3)Ph, 3h). Single-crystal X-ray structure analyses of 3d, 3f, and 3g were carried out, which established the coordination of an imidoylketeneimene fragment to the metal center. The reaction of 1 with alkyl isocyanides bearing H atoms α to the NC group leads to a sequential coupling of 3 molar equiv of the isocyanide with the imido complex, yi...