Substituted 1,4-Diaza-1,3-butadiene Monocyclopentadienyl Titanium Complexes. Crystal Structure of Ti(η⁵-C₅Me₅)(η⁴-ⁱPrNCHCHNⁱPr)Me

Abstract

We report the synthesis of 1,4-diaza-1,3-butadiene (dad) complexes Ti(η 5 -C 5 R 5 )(η 4 -R′ 2 -dad)-Cl (R ) H, Me; R′ ) i Pr, t Bu) by reaction of Ti(η 5 -C 5 R 5 )Cl 3 (R ) H, Me) with the dilithium salts of diisopropyl-and di-tert-butyl-substituted 1,4-diaza-1,3-butadienes (Li 2 [R′ 2 -dad]). Alkylation of the pentamethylcyclopentadienyl diisopropyl and di-tert-butyl derivatives with methylmagnesium chloride and methyllithium gave complexes Ti(η 5 -C 5

Reactivity variations within Group 4 complexes of 1,4-di-tert-butyl-1,4-diazabuta-1,3-diene: Structures of [(C5H5)TiCl{(t-BuNCH)2}] and [(C5H5)2Zr{(t-BuNCH)2}]

“…For compound 1, two isomers are observed at room temperature in the 1 H NMR spectrum, which has previously been noted [4] as relating to a ring flipping process of the non-planar TiN 2 C 2 chelate ring that gives rise to two isomers (ring leaning towards the cyclopentadienyl ring, prone conformation, or the chloride ligand, supine conformation [15]), Scheme 2. The spectrum of 1 exhibits very broad resonances for the cyclopentadienyl and methine protons of the t-Bu-DAB ligand, and overlapping t-butyl proton resonances of the t-Bu-DAB ligand of each isomer.…”

“…For compound 1, routes include both the reaction of [ (C 5 H 5 )TiCl 3 ] with Li 2 (t-Bu-DAB) [4] [6]. In each of these cases, the source of the 1,4-diazabuta-1,3-diene was from a doubly reduced dianion precursor, whereas our syntheses utilised a radical anion 1,4-diazabuta-1,3-diene precursor, [Li(t-Bu-DAB) 2 ], and are the first reactions to demonstrate the elimination of the cyclopentadienyl anion.…”

“…Homoleptic mono-, bis-and tris(1,4-diazabuta-1,3-diene)metal complexes are known for a large range of metals (the mono-derivatives being better known as Arduengo-type carbene analogues), as are heteroleptic complexes [1,3]. Herein, we report on new syntheses and further characterisation of a series of Group 4 heteroleptic complexes of t-Bu-DAB and discuss the chemistry of these complexes (previous syntheses and some fluxional behaviour of these complexes have been reported [4][5][6]). …”

A Critical Review of Electronic Effects in Enediamido and α‐Diimino Complexes of the Group 4 Metals

“…As underlined before, DAD behaves as the equivalent of a six-electron donor by exploiting a filled combination of the N pπ orbitals for the third σ-type donation. [30] WEVVUO [31] WEVWAV [31] YADBEL [32] YADBIP [32] [CpTi(DAD)(NR 2 )] WORGIT [33] YAJCIV [34] [CpЈZr(DAD)(NR 2 )] NETZAN [35] NETZER [35] [Cp*Ti(DAD)(CN)] FAFMIJ [36] CpMR [Cp*Ti(DAD)(CH 3 )] ICEGUS [37] [CpTi(DAD)(CH 2 Ph)] QULSAR [38] CpML 2 [CpЈZr(DAD)(allyl)] POWVEC [39] [CpZr(DAD)(acetylacetoneiminato)] QULRIY [38] [Cp*Hf(DAD)Cl(L)] (L = imino YADYEH [40] group) [CpЈZr(DAD)(NR 2 )(NHR 2 )] WOJLAI [29] [42] JOFCIQ [43] [CpЈ 2 Zr(DAD)] FATBAD [44] HISWIP [45] JOYXIE [46] SINCAT [47] VIZWEG [48] VIZWIK [48] BAMQUC [49] [Cp 2 Hf(DAD)] QULRUK [38] [a] Cp* = C Two of the complexes in Table 3 are exceptional in that they contain a planar M(DAD) metallacycle. Their simplified formulae are [CpЈZr(NR 2 )(NHR 2 )(DAD)] and [CpЈZrCl(NHR 2 ) 2 (DAD)] (see Figure 6) and refer to the species WOJLAI and WOJLEM, [29] respectively.…”

Synthesis and reactivity of di(silylamido)cyclopentadienyl titanium and zirconium complexes

“…5) shows the titanium atom at the centre of a distorted pseudotetrahedral coordination with the five-membered TiN 2 C 2 ring of the dad ligand folded along the N(3)-N(4) axis providing the less favourable prone orientation observed for dad-Ti (dad = RN-CH@CH-NR) compounds in solution [31,32], forced by the bond to the pendant amido group, in contrast with the supine conformation reported for group 4 enediamido complexes [30][31][32][33].…”