Mechanism of the Reaction of Alkynes with a “Constrained Geometry” Zirconaaziridine. PMe₃ Dissociates More Rapidly from the Constrained Geometry Complex than from its Cp₂ Analogue

Abstract

The "constrained geometry" (cg) zirconaaziridines Me 4 C 5 SiMe 2 N(tBu)Zr-(η 2 )-[N(Ph)CH(Ph)](PMe 2 R) (R ) Me, Ph) have been synthesized, and the R ) Ph derivative has been structurally characterized by X-ray crystallography. Treatment of these zirconaaziridines with unsaturated electrophiles such as diphenylacetylene results in insertion. Kinetic data for these irreversible reactions indicate that PMe 3 dissociation must occur prior to insertion and that PMe 3 dissociation from the cg zirconaaziridine 4a is faster (k 1 ) 0.204(7) s -1 ) than from the Cp 2 zirconaaziridine 5a (k 1 ′ ) 0.0013(1) s -1 ). The reaction of 4a with diphenylacetylene is several orders of magnitude faster than the reaction of 5a with diphenylacetylene.

Cyclic Ureate Tantalum Catalyst for Preferential Hydroaminoalkylation with Aliphatic Amines: Mechanistic Insights into Substrate Controlled Reactivity

“…Mixed alkyl amido complexes are known precursors to metallaziridine complexes. 30 These observations show that ligand substitution reactions can be to the rapid and sequential formation of a metallaziridine intermediate (Scheme 7) in which the precatalyst coordinates an incoming amine to protonate off one TMS group, followed by tantalaaziridine formation and release of deuterated TMS. This process continues until all alkyl groups are replaced by the corresponding amido ligands.…”

Imines in the Titanium Coordination Sphere: Highly Reactive Titanaaziridines and Larger Titanacycles Formed by Subsequent C–C Coupling Reactions

“…[8,9,12] Zirconaaziridines undergo insertion reactions into the M-C bond with several substrates containing C-X multiple bonds, [9,15,[32][33][34] whereas the chemistry of titanaaziridines is Scheme 8. Reactivity of the titanoceneaziridines 3a-c.…”

Conversion of imine ligands in allyl–nickel(II) complexes

“…Diimine ligands allow an extensive varying both the geometric and donor-acceptor properties of catalytically active complexes and thereby a control over properties of the prepared catalysts [9][10][11][12][13][14][15][16][17][18]. This gave a great impetus to syntheses of a wealth of new diimine ligands and their metallo-complexes with different transition metals [19][20][21][22][23][24][25][26][27][28][29][30][31][32].…”