Synthesis, Structures and Reactivity of Group 4 Hydrazido Complexes Supported by Calix[4]arene Ligands

Reaction of TiCl2(Me2Calix) with 2 equiv of LiNHNRR′ afforded the corresponding terminal hydrazido(2-) complexes Ti(NNRR′)(Me2Calix) (R = Ph, R′ = Ph (1) or Me; R = R′ = Me (3)) which were all structurally characterized. The X-ray structure of Ph2NNH2 is reported for comparison. Compound 1 was also prepared from Na2[Me2Calix] and Ti(NNPh2)Cl2(py)3. Reaction of ZrCl2(Me2Calix) with 2 equiv of LiNHNR2 afforded only the bis(hydrazido(1-)) complexes Zr(NHNR2)2(Me2Calix) (R = Ph or Me). Treatment of Ti(NNMe2)(Me2Calix) (3) with MeI gave the zwitterionic hydrazidium species Ti(NNMe3)(MeCalix) (6) via a net isomerization reaction which was found to be catalytic in MeI. The corresponding reaction of 3 with CD3I gave Ti(NNMe2CD3)(MeCalix) (6-d3) with concomitant elimination of MeI. Reaction of 3 with 1 equiv of MeOTf gave [Ti(NNMe3)(Me2Calix)][OTf] (7-OTf) which in turn reacted with nBu4NI to form 6 and MeI. Addition of PhCHO to 3 gave the μ-oxo dimer [Ti(μ-O)(Me2Calix)]2 and benzaldehyde-dimethylhydrazone. Reaction of either 3 or 6 with tBuNCO gave the zwitterionic species Ti{tBuNC(NNMe3)O}(MeCalix) (10) which has been crystallographically characterized. Compound 10 is the formal product of insertion of an isocyanate into the TiNα bond of a titanium hydrazide or hydrazidium species (Me2Calix or MeCalix = dianion or trianion of the di- or monomethyl ether of p-tert-butyl calix[4]arene, respectively).