Ion Pairing in Ti(IV) Trisamidotriazacyclononane Compounds

Martins, Ana M.; Ascenso, José R.; Costa, Sı́lvia M. B.; Dias, Alberto R.; Ferreira, Humberto; Ferreira, José A. B.

doi:10.1021/ic0510258

Cited by 12 publications

(19 citation statements)

References 31 publications

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“…Following our own efforts in the study of group 4 metal complexes supported by nitrogen-based ancillary ligands, some of us have recently reported on the preparation of trans -disubstituted cyclam-based ligand precursors and their coordination chemistry to zirconium . The saturated backbone of the macrocyclic ligand confers an enhanced flexibility when compared to its unsaturated congeners, such as porphyrins or tetraazaannulenes .…”

Section: Introductionmentioning

confidence: 99%

Structure and Reactivity of Neutral and Cationic trans-N,N′-Dibenzylcyclam Zirconium Alkyl Complexes

Munhá

Antunes²,

Alves³

et al. 2010

Organometallics

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Reactions of (Bn 2 Cyclam)ZrCl 2 (1) (where Bn 2 Cyclam = trans-N,N 0 (PhCH 2 ) 2 Cyclam) with appropriate alkylating reagents produced (Bn 2 Cyclam)ZrR 2 (R = Me (2), CH 2 Ph (3), n Bu (4), CCPh (5)). Activation of the ortho C-H bond of the two macrocycle benzyl substituents in complexes 2, 3, and 4 was thermally induced, leading to the formation of a bis(ortho-metalated) complex, ((C 6 H 4 CH 2 ) 2 Cyclam)Zr ( 6). This reaction proceeds along with RH elimination and converts the original dianionic tetracoordinated cyclam in a tetraanionic hexacoordinated ligand where two new Zr-C Ph bonds complete the metal sphere. Treatment of 6 with one equivalent of HCtCPh led to ((C 6 H 4 CH 2 )BnCyclam)Zr(CCPh) ( 7) via protonation of one Zr-C Ph bond by phenylacethylene. Further reaction of 7 with an excess of HCtCPh led to 5. The reactions of 2 and 3 with B(C 6 F 5 ) 3 are strongly solvent dependent. Solvent-stabilized cationic species of formula [(Bn 2 Cyclam)ZrR(Solv)]-[RB(C 6 F 5 ) 3 ] were obtained from reactions of 2 in CD 2 Cl 2 (10) or d 8 -THF ( 12) and from 3 in d 8 -THF (9). The reactions of 3 in CD 2 Cl 2 or d 8 -toluene gave [(Bn 2 Cyclam)Zr(η 2 -CH 2 Ph)][ PhCH 2 B(C 6 F 5 ) 3 ] (8). Finally, the reaction of 2 in d 8 -toluene led to [(Bn 2 Cyclam)Zr(C 6 F 5 ){CH 2 B(C 6 F 5 ) 2 }] (14); the precursor of the latter is the zwitterionic [(Bn 2 Cyclam)Zr(CH 3 ){CH 3 B(C 6 F 5 ) 3 }] (11), which then undergoes methane elimination and C 6 F 5 migration from boron to zirconium. The mechanism of this reaction was studied by DFT and revealed that (i) methane elimination is assisted by one alphaagostic C-H bond and (ii) migration of the C 6 F 5 ring is supported by one bridging fluorine bond between the zirconium and one of the C 6 F 5 rings that remains bonded to boron.

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Section: Introductionmentioning

confidence: 99%

Structure and Reactivity of Neutral and Cationic trans-N,N′-Dibenzylcyclam Zirconium Alkyl Complexes

Munhá

Antunes²,

Alves³

et al. 2010

Organometallics

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“…The subject of ion pairing is a recurring theme in many areas of chemistry with examples from water-soluble polyanionic dendrimers, [1] sulfated glycoproteins [2] and alkali metal complexes of ionophore antibiotics, [3] all having recently appeared. In addition, there are an increasing number of studies on transition metal salts and we note examples from iridium, [4,5] cobalt, [6] ruthenium, [7] manganese, [8] palladium, [9] and titanium, [10] to name just a few.…”

Section: Introductionmentioning

confidence: 99%

Ion Pairing and Salt Structure in Organic Salts through Diffusion, Overhauser, DFT and X‐ray Methods

Moreno

Pregosin

Veiros³

et al. 2009

Chemistry A European J

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Pulsed gradient spin-echo (PGSE) diffusion characteristics for a) the new [brucinium][X] salts 6 a-f [a: X = BF(4)(-); b: X = PF(6)(-); c: X = MeSO(3)(-), d: X = CF(3)SO(3)(-); e: X = BArF(-); f: X = PtCl(3)(C(2)H(4))(-)], b) 4-tert-butyl-N-benzyl analogue, 7 and c) the aryl carbocations (p-R-C(6)H(4))(2)CH 9 a (R = CH(3)O) and 9 b (R = (CH(3))(2)N), (p-CH(3)O-C(6)H(4))(x)CPh(3-x)(+) 10 a-c (x = 1-3, respectively) and (p-R-C(6)H(4))(3)C(+) 11 (R = (CH(3))(2)N) and 12 (R = H) all in several different solvents, are reported. The solvent dependence suggests strong ion pairing in CDCl(3), intermediate ion pairing in CD(2)Cl(2) and little ion pairing in [D(6)]acetone. (1)H, (19)F HOESY NMR spectra (HOESY: heteronuclear Overhauser effect spectroscopy) for 6 and 7 reveal a specific approach of the anion with respect to the brucinium cation plus subtle changes, which are related to the anion itself. Further, for carbocations 9-12, (all as BF(4)(-) salts) based on the NOE results, one finds marked changes in the relative positions of the BF(4)(-) anion. In these aryl cationic species the anion can be located either a) very close to the carbonium ion carbon b) in an intermediate position or c) proximate to the N or O atom of the p-substituent and remote from the formally positive C atom. This represents the first example of such a positional dependence of an anion on the structure of the carbocation. DFT calculations support the experimental HOESY results. The solid-state structures for 6 c and the novel Zeise's salt derivative, [brucinium][PtCl(3)(C(2)H(4))], 6 f, are reported. Analysis of (195)Pt NMR and other NMR measurements suggest that the eta(2)-C(2)H(4) bonding to the platinum centre in 6 f is very similar to that found in K[PtCl(3)(C(2)H(4))]. Field dependent T(1) measurements on [brucinium][PtCl(3)(C(2)H(4))] and K[PtCl(3)(C(2)H(4))], are reported and suggested to be useful in recognizing aggregation effects.

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“…[87] . [88] Rupture of the N À Si bond in silazanes concurrent with Ti=N bond formation can also be accomplished with strained systems [89,90] and with the aid of nucleophiles. [91,92] In the case of nucleophiles, the cyclometallated salt [Na( [12] [91] Other strained N À Si linkages in monoanionic ligands such as [92] One-electron oxidation can also promote trimethylsilyl chloride elimination.…”

Section: Trimethylsilyl Chloride Elimination Reactionsmentioning

confidence: 99%

“…For these last cases, the use of THF as solvent results in formation of edge‐sharing octahedral dimers such as [{Cl(μ 2 ‐Cl)(thf) 2 TiNR} 2 ] 88. Rupture of the NSi bond in silazanes concurrent with TiN bond formation can also be accomplished with strained systems89, 90 and with the aid of nucleophiles 91. 92 In the case of nucleophiles, the cyclometallated salt [Na([12]crown‐4) 2 ][(Me 3 Si) 2 N] 2 TiCH 2 SiMe 2 N(SiMe 3 )] can be disilylated (also resulting in oxidation to Ti IV ) at the cyclometallated NSi linkage with HCCPh to afford the imide–alkyl salt [Na([12]crown‐4) 2 ][{(Me 3 Si) 2 N} 2 TiNSiMe 3 (CH 2 SiMe 2 CCPh)] (Scheme ) 91…”

Section: Trimethylsilyl Chloride Elimination Reactionsmentioning

confidence: 99%

The Progression of Synthetic Strategies to Assemble Titanium Complexes Bearing the Terminal Imide Group

Fout¹,

Kilgore²,

Mindiola³

2007

Chemistry A European J

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The synthesis of terminal titanium imides is described in this account. The incorporation of this functional group has evolved from more simplistic approaches to more complex or unusual methods. Past and current synthetic strategies to incorporate the terminal imide functionality are explained with particular emphasis on low-coordinate titanium environments bearing this ubiquitous but vital type of motif. More recently, the imide functionality has demonstrated to be a key intermediate for modeling important industrial processes such as the hydrodenitrogenation of crude oil.

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Ion Pairing in Ti(IV) Trisamidotriazacyclononane Compounds

Cited by 12 publications

References 31 publications

Structure and Reactivity of Neutral and Cationic trans-N,N′-Dibenzylcyclam Zirconium Alkyl Complexes

Structure and Reactivity of Neutral and Cationic trans-N,N′-Dibenzylcyclam Zirconium Alkyl Complexes

Ion Pairing and Salt Structure in Organic Salts through Diffusion, Overhauser, DFT and X‐ray Methods

The Progression of Synthetic Strategies to Assemble Titanium Complexes Bearing the Terminal Imide Group

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