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

Abstract

The synthesis and reactivity of titanium diphenyl hydrazido(2−) complexes supported by the diamido-ether ligands O(2-C6H4NSiMe3)2 (N2 ArO) and O(CH2CH2NSiMe3)2 (N2O) are described. Reaction of Li2N2 ArO or Li2N2O with Ti(NNPh2)Cl2(py)3 afforded Ti(N2 ArO)(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-C6H3 iPr2) 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 = N2 ArO or N2O) containing hydrazonamide ligands. Reaction of 14 with XylNC (Xyl = 2,6-C6H3Me2) gave only the isonitrile σ-adduct Ti(N2 ArO)(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.

Elusive Terminal Copper Arylnitrene Intermediates

“…These data are consistent with insertion of MeCN into [Cu]=NAr to give the κ 2 ‐diazametallocyclobutene 8 . Such nitrile insertion into [M]=NR functionalities is quite uncommon, though previously observed in the reaction of nucleophilic metal‐imides [Ti]=NR, [U]=NR with organonitriles R′C≡N –. Amidine products RNHC(=NTs)Me have been observed in C−H amidation of substrates R‐H with PhI=NTs carried out in MeCN with Mn, Fe, and Cu‐based catalysts,, suggested to proceed via [M](κ 2 ‐ N , N ‐NC(Me)NTs) intermediates …”

Structural Diversity in the Reactions of Dimetallic Alkyl Titanium Oxides with Isonitriles and Nitriles

“…Analogously, this spectrum reveals two resonances for the methyl groups bound to titanium (0.30 and 0.29 ppm), two signals for the methyl groups of the azatitanacyclopropane unit at δ 1.32 and 1.85, and one signal (0.52 ppm) for the methyl groups of the SiMe 3 fragment, in accord with the asymmetry of 13 . Moreover, the existence of the isocyanide ligand is confirmed by a stretching band for the CN bond at 2036 cm –1 in the IR spectrum, comparable to those found in Ti­(IV) complexes with coordinated isocyanides. ,− …”

Reactions of Titanium Imides and Hydrazides with Boranes

“…In general, the dominant feature of these compounds is their addition or insertion reactions with unsaturated compounds at the M–N α multiple bond itself (best described as a σ 2 π 4 triple bond). For certain hydrazido, alkylidene hydrazido, and tert -butoxyimido , compounds, reductive cleavage of the N α –N β or N α –O β bond can occur with reducing substrates such as CO, isonitriles, and alkynes. Less commonly, dating from Bergman and Wolczanski’s first reports on these compounds, Group 4 imides can also activate the C–H bonds of organic substrates, and also the H–H bond of H 2 .…”