Cyclopentadienyl, indenyl and bis(cyclopentadienyl) titanium imido compounds

Abstract

The titanium tert-butyl imido compounds [Ti(NBu t )Cl 2 (NC 5 H 4 R-4) n ] (R = H, n = 2 or 3; R = Bu t , n = 2) have been found to be entry points to the half-sandwich η 5 -cyclopentadienyl derivatives [Ti(η 5 -C 5 RЈ 4 RЉ)(NBu t )Cl(NC 5 H 4 R-4)] (R = Bu t , RЈ = RЉ = H or Me; R = H, RЈ = H, RЉ = H, Me or Pr i ; R = H, RЈ = Me, RЉ = Me, Et or C 4 H 7 ), the η 5 -1,2,3-trimethylindenyl species [Ti(η 5 -C 9 H 4 Me 3 )(NBu t )Cl(NC 5 H 4 Bu t -4)] and the bis(η 5 -cyclopentadienyl) compound [Ti(η 5 -C 5 H 5 ) 2 (NBu t )(NC 5 H 5 )], the crystal structure of which has been determined. The complex [Ti(η 5 -C 5 H 5 )(NBu t )Cl(NC 5 H 5 )] readily loses pyridine under vacuum in the solid state to form the binuclear complex [Ti 2 (η 5 -C 5 H 5 ) 2 (µ-NBu t ) 2 Cl 2 ]. Treatment of [Ti(η 5 -C 5 Me 4 R)(NBu t )Cl(NC 5 H 5 )] (R = Me or Et) with Na[C 5 H 5 ] gives the corresponding mixed-ring sandwich derivatives [Ti(η 5 -C 5 H 5 )(η 5 -C 5 Me 4 R)(NBu t )Cl(NC 5 H 5 )]. Addition of Li[C 9 H 7 ] to [Ti(η 5 -C 5 H 5 )(NBu t )Cl(NC 5 H 5 )] gave the η 5 -cyclopentadienyl, η 3 -indenyl mixed-ring analogue [Ti(η 5 -C 5 H 5 )(η 3 -C 9 H 7 )(NBu t )(NC 5 H 5 )]. The complex [Ti(η 5 -C 5 H 5 ) 2 (NBu t )(NC 5 H 5 )] undergoes a roomtemperature cyclopentadienyl ligand-redistribution reaction with [Ti(NBu t )Cl 2 (NC 5 H 5 ) 2 ] forming [Ti(η 5 -C 5 H 5 )(NBu t )Cl(NC 5 H 5 )] in quantitative yield. Variable-temperature NMR spectra for the half-sandwich complexes show that the co-ordinated pyridine exchanges with free pyridine via an associative mechanism. The compound [Ti(η 5 -C 5 H 5 )(η 5 -C 5 Me 4 Et)(NBu t )(NC 5 H 5 )] is also fluxional and exhibits reversible pyridine dissociation at higher temperatures and restricted rotation about the Ti᎐N (pyridine) bond at lower temperatures.

Sandwich and Half‐Sandwich (Imido)niobium Complexes

“…Indeed, such lengthening has also been observed in (imido)metallocene complexes of titanium [48] and molybdenum. [47] The bonding in the ''19-electron'' vanadium complex [V(ϭNC 6 H 3 Me 2 -2,6)(η 5 -C 5 Me 5 ) 2 ] has previously been studied by molecular orbital calculations and led to the proposal that the surplus electrons in these ''high-electron'' complexes are located in essentially ligand-based orbitals and thus the 18-electron rule [53] [Nb(ϭO)CpЈ 2 Me] 2.181 [54] [Nb(ϭNPh)CpЈ 2 (CϵCPh)]] (37) 2.180 [55] [Nb(ϭNPh)CpЈ 2 Cl] (9) 2.180 [37] [NbCpЈ 2 Cl(η 2 -N,C-OCNPh)] 2.121 [53] [NbCpЈ 2 Cl 2 ] 2.079 [54,56] [{NbCpЈ 2 Cl} 2 ] 2.07 [37] [NbCpЈ 2 (C 6 F 5 )(CO)] 2.04 [54] is not violated.…”

Cuboidal Mo3S4 and Mo3NiS4 Complexes Bearing Dithiophosphates and Chiral Carboxylate Ligands: Synthesis, Crystal Structure and Fluxionality

“…Identical bimolecular pyridine exchange has been observed for [CpTi-(BuN)Cl(py)] in the presence of added pyridine. [44] For closely related pyridine exchange processes, line-shape analysis or quantitative EXSY spectroscopy have proven to be very useful for obtaining a detailed insight into the intimate mechanistic picture of the process. For example, for palladium complexes featuring 2,2Ј-bipyridyl and substituted pyridine ligands of general formula [Pd(bipy)(py) 2 ] 2+ or [Pt(bipy)(py) 2 ] 2+ , the mechanistic picture (dissociative exchange of hindered rotation-mediated pyridine exchange) of the pyridine exchange is dramatically affected by the identity of the substituent in the pyridine ligand and is associated with syn/anti inversion.…”

Synthesis, Bonding and Reactivity of a Terminal Titanium Alkylidene Hydrazido Compound

“…www.chemeurj.org scale and therefore it was characterised in situ by using 1 H and 13 C NMR spectroscopy at 248 K. The assignment of 9 as a [2+2] cycloaddition product is supported by the 1 H and 13 C NMR data and by analogy to its imido and hydrazido analogues,…”