Site selectivity and reversibility in the reactions of titanium hydrazides with Si-H, Si-X, C-X and H+ reagents: Ti=N(α) 1,2-silane addition, Nβ alkylation, Nα protonation and σ-bond metathesis.

We report a combined experimental and computational comparative study of the reactions of the homologous titanium dialkyl- and diphenylhydrazido and imido compounds Cp*Ti{MeC(N(i)Pr)(2)}(NNR(2)) (R = Me (1) or Ph (2)) and Cp*Ti{MeC(N(i)Pr)(2)}(NTol) (3) with silanes, halosilanes, alkyl halides and [Et(3)NH][BPh(4)]. Compound 1 underwent reversible Si-H 1,2-addition to Ti=N(α) with RSiH(3) (experimental ΔH ca. -17 kcal mol(-1)), and irreversible addition with PhSiH(2)X (X = Cl, Br).

Reaction site diversity in the reactions of titanium hydrazides with organic nitriles, isonitriles and isocyanates: Ti=N(α) cycloaddition, Ti=N(α) insertion and N(α) -N(β) bond cleavage.

We report a range of new transformations of the diamide-amine supported Ti=NNPh(2) functional group with a variety of unsaturated substrates, along with DFT studies of the key mechanisms. Reaction of [Ti(N(2) N(py) )(NNPh(2) )(py)] (4, N(2) N(py) =(2-NC(5) H(4) )CMe(CH(2) NSiMe(3) )(2) ; py=pyridine) with MeCN gave the dimeric species [Ti(2) (N(2) N(py) )(2) {μ-NC(Me)(NNPh(2) )}(2) ] through a [2+2] cycloaddition process. Reaction of 4 or [Ti(N(2) N(Me) )(NNPh(2) )(py)] (5, N(2) N(Me) =MeN(CH(2) CH(2) NSiMe(3) )(2) ) with fluorinated benzonitriles gave the terminal hydrazonamide complexes [Ti(N(2) N(R) ){NC(Ar F x)NNPh(2) }(py)] (R=py or Me; Ar F x=2,6-C(6) H(3) F(2) or C(6) F(5) ).

M=N(alpha) cycloaddition and N(alpha)-N(beta) insertion in the reactions of titanium hydrazido compounds with alkynes: a combined experimental and computational study.

A combined experimental and DFT study of the reactions of diamide-amine supported titanium hydrazides with alkynes is presented. Reaction of Ti(N2N(py))(NNPh2)(py) (1, N2N(py) = (2-NC5H4)CMe(CH2NSiMe3)2) with terminal and internal aryl alkynes ArCCR (Ar = Ph or substituted phenyl, R = Me or H) at room temperature gave the fully authenticated azatitanacyclobutenes Ti(N2N(py)){N(NPh2)C(R)CAr} via ArCCR [2 + 2] cycloaddition to the Ti=N(alpha) bond of the hydrazide ligand. In contrast, reaction of 1 with PhCCMe at 60 degrees C, or of Ti(N2NMe)(NNPh2)(py) (11, N2NMe = MeN(CH2CH2NSiMe3)2) with RCCMe (R = Me, Ph or substituted phenyl) at room temperature or below, gave vinyl imido compounds of the type Ti(N2N(R')){NC(R)C(Me)NPh2}(py), in which RCCMe had undergone net insertion into the N(alpha)-N(beta) bond.

Single and double substrate insertion into the Ti=N(alpha) bonds of terminal titanium hydrazides.

Nitriles, CO(2) and isocyanates undergo net single or double insertion reactions into the Ti=N(alpha) multiple bonds of terminal titanium hydrazides. These are the first such examples of this type of reactivity for any transition metal hydrazide complex.

Synthesis, structures and reactivity of group 4 hydrazido complexes supported by calix[4]arene ligands.

Reaction of TiCl(2)(Me(2)Calix) with 2 equiv of LiNHNRR' afforded the corresponding terminal hydrazido(2-) complexes Ti(NNRR')(Me(2)Calix) (R = Ph, R' = Ph (1) or Me; R = R' = Me (3)) which were all structurally characterized. The X-ray structure of Ph(2)NNH(2) is reported for comparison. Compound 1 was also prepared from Na(2)[Me(2)Calix] and Ti(NNPh(2))Cl(2)(py)(3).

Cycloaddition reactions of transition metal hydrazides with alkynes and heteroalkynes: coupling of Ti=NNPh2 with PhCCMe, PhCCH, MeCN and tBuCP.

The first structurally authenticated [2+2] cycloaddition products of any transition metal hydrazide complexes are reported; cycloaddition products of transition metal hydrazides with alkynes and heteroalkynes have been obtained for the first time; these are the first structurally authenticated cycloaddition products for any transition metal M=NNR(2) functional group.

New ligand platforms for developing the chemistry of the Ti=N-NR2 functional group and the insertion of alkynes into the N-N bond of a Ti=N-NPh2 ligand.

Two broadly applicable strategies for extending the available ligand platforms of the virtually unexplored terminal Ti=N-NR2 functional group are described, along with the highly selective room temperature insertion of alkynes into the N-N bond of Ti{MeN(CH2CH2NSiMe3)2}(NNPh2)(py) and the catalytic cis-diamination of PhC[triple bond]CMe by diphenylhydrazine.

A remarkable inversion of structure-activity dependence on imido N-substituents with varying co-ligand topology and the synthesis of a new borate-free zwitterionic polymerisation catalyst.

Ethylene polymerisation productivities of tris(pyrazolyl)methane-supported catalysts [Ti(NR){HC(Me2pz)3}Cl2] show a dramatically different dependence on the imido R-group compared to those of their TACN analogues, attributed to differences in fac-N3 donor topology; when treated with AliBu3, the zwitterionic tris(pyrazolyl)methide compound [Ti(N-2-C6H4tBu){C(Me2pz)3}Cl(THF)] also acts as a highly active, single site catalyst (TACN = 1,4,7-trimethyltriazacyclononane).