Synthesis and reactions of (tert-butylimido)bis(η-cyclopentadienyl)niobium cations: NMR evidence for d0 olefin cations [Nb{(η-C5H5)2}(NtBu)(η-C2H4)][B(C6F5)4] and [Nb{(η-C5H4)CMe2(η-C5H4)}(NtBu)(η-C2H3Me)][B(C6F5)4]

Neutral and Cationic Alkyl Tantalum Imido Complexes: Synthesis and Migratory Insertion Reactions

“…In addition, the difference in 13 C NMR chemical shifts between the quaternary carbons and the methyl carbons of the tert -butyl imido groups of 1 and 2 are 34.8 and 34.0, respectively. These differences have previously been used to characterize imido−metal bonds, and larger values have been shown to correspond to greater degrees of π-donation. , The values for 1 and 2 place these complexes at the high end of the reported scale and corroborate the assignment of the imido groups as X 2 L ligands.…”

“…The zwitterion 7 is stabilized by η 6 -coordination of the benzyl borate anion, and the salt 8 is stabilized by Lewis base coordination. To synthesize a cationic tantalum imido complex without the stabilizing effect of η 6 -aryl or pyridine coordination, the alkide abstraction reagent [Ph 3 C][B(C 6 F 5 ) 4 ] was used to abstract a benzyl group from 1 . ,, …”

“…Dihydrogen, phenylacetylene, and the methyl group of a Cp* ligand have been observed to add across the imido bond of this salt. Hermann and co-workers have also synthesized an amine-coordinated cationic tantalum imido complex by protonation of an amide group at a tantalum center with [PhNHMe 2 ][BPh 4 ], and Green has observed ethylene coordination to a cationic niobocene complex by NMR spectroscopy . In addition, Meyer and co-workers have abstracted a chloride ligand from an amidinate tantalum imido complex to form an SbF 6 - salt .…”

More than Bystanders: The Effect of Olefins on Transition‐Metal‐Catalyzed Cross‐Coupling Reactions

“…Stoebenau and Jordan, [15] among others, [16] determined the binding constants of various olefins to early transition metals. The equilibrium constants for the binding of a series of olefins to cationic Zr IV species 2 are provided in Scheme 6.…”

Synthesis, Characterization, and Reactivity of Niobium and Tantalum Complexes Bearing Metal−Nitrogen Bonds. X-ray Molecular Structure of [Nb(C5H4SiMe3){NH(CH2)2-η-NH2}Cl3] and the Novel Tetranuclear Niobium Oxo Derivative [{Nb(C5H4SiMe3)Cl(μ2-O)}4(Cl)2(μ3-O)]

“…Transition-metal compounds bearing amido and imido ligands acting as a reactive site − continue to generate a great deal of interest − because of their crucial role in many catalytic and stoichiometric reactions, − such as in olefin metathesis, , amido- and imido-based Ziegler−Natta olefin polymerization, − and ring-opening metathesis polymerization. − In addition, due to their strong π-donating capability and relative inertness, these groups have been widely used as convenient ancillary or supporting ligands to stabilize high-oxidation-state early-transition-metal complexes. − Consequently, recent decades have witnessed significant progress in the organometallic chemistry of half-sandwich imido complexes of group 5 metals, − which has largely been stimulated by the isolectronic relationship , between these complexes and the very well known group 4 bent metallocenes extensively used as Ziegler−Natta catalysts. − Among the various methods developed for the synthesis of compounds of this kind, simple and efficient routes are the reactions of metal halides with lithium amides or organic amines. ,, …”