Syntheses, structures, and reactivities of unusual four-membered metallacycles formed in insertion reactions of N:N:O, N:N:NR, and N:N:CR2 with (.eta.5-C5Me5)2Zr(C2Ph2)

Abstract

compassing data collection and solution/refinement, atomic coordinates, isotropic and anisotropic temperature factors, hydrogen atom coordinates, bond lengths, and bond angles (10 pages); tables of observed and calculated structure factors (36 pages). Ordering information is given on any current masthead page.

Functionalization of Complexed N2O in Bis(pentamethylcyclopentadienyl) Systems of Zirconium and Titanium

“…One interesting feature associated with the molecular structure of 1 is the retention of an azoxymetallacyclobutene ring in Cp* 2 Zr(N(O)NPhCCPh), a previously reported unstable complex that eluded crystallographic analysis due to its propensity to eject N 2 and subsequently form the oxymetallacyclobutene compound (Scheme 1 ). 12 In addition, the solid-state structure confirms methylation of the β-N position of the metallacycle (N(2)–C(1), 1.457(8) Å). For comparison, the N(1)–N(2) distance of 1.318(7) Å in the azoxymetallacycle fragment is relatively elongated from that of the titanium and neutral analogue, Cp* 2 Ti(N(O)NCPhCPh).…”

“… 3 − 21 Unfortunately, and as noted before, this molecule is kinetically inert due to its poor properties as a ligand, 22 − 24 consequently resulting in only a handful of systems being capable of complexing N 2 O without the entropic and enthalpic driving force to N 2 ejection and metal oxo formation. 11 , 12 , 18 , 22 − 31 Thus, the use of N 2 O as an oxidizing substrate in transition metal chemistry is often hampered by a combination of kinetic inertness and inevitable oxidation of the metal center, concomitant with entropy-assisted loss of a thermodynamically stable molecule such as dinitrogen. 32 …”

Reactivity of C1‐Symmetric Heteroarylamido Hafnium Complexes towards Unsaturated Electrophilic Molecules: Development of New Families of Olefin Polymerization Catalysts

“…It should be noted that only a few mononuclear Group 4 metal complexes that bear the triazenido fragment have been structurally characterized, and most of them have an η 2 ‐bound triazenido group with α‐ and γ‐nitrogen atoms connected to the metal –. Other examples include complexes that bear η 1 ‐γ‐ and η 2 ‐α,β ‐ triazenido fragments –. The proposed η 2 ‐β,γ‐bonding of the triazenido group, in our case, can be explained by the steric repulsion of the trimethylsilyl moiety at the triazenido group with the isopropyl group of the aniline, which hinders the more commonly observed α,γ‐bonding of the triazenido fragment.…”

Nitrogen Monoxide and Nitrous Oxide Binding and Reduction

“…Oxotransfer from N 2 O can lead to formation of metal-oxo complexes or oxidation of ligands contained in the metal complex. In pioneering research of N 2 O reactivity, Bottomley and coworkers [188][189][190][191][192] N 2 O insertion into a metal-ligand bond has been observed with Group IV metallocene complexes (Scheme 2.9) [194]. When reported, these transformations were unprecedented since reactions between N 2 O and metal complexes usually lead to extrusion of N 2 .…”