Migratory Aptitude of the Zr-C Functionalities Bonded to a Macrocyclic Structure: Thermally- and Solvent-Assisted Intra- and Intermolecular Migrations in Dialkyl(dibenzotetramethyltetraazaannulene)zirconium(IV)

Giannini, Luca; Solari, Euro; Angelis, Stefania De; Ward, Thomas R.; Floriani, Carlo; Chiesi‐Villa, Angiola; Rizzoli, Corrado

doi:10.1021/ja00126a019

Cited by 86 publications

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“…[Ce(tmtaa) 2 ] (3). Ce 2 (tmtaa) 3 or Ce(tmtaa)(tmtaaH) were converted to Ce(tmtaa) 2 6 ] or 1,4-benzoquinone as outlined below. Method 1: Ce(tmtaa)(tmtaaH) (0.15 g, 0.18 mmol) was suspended in toluene (ca.…”

Section: Methodsmentioning

confidence: 99%

Synthesis and magnetic properties of cerium macrocyclic complexes with tetramethyldibenzotetraaza[14]annulene, tmtaaH2

2006

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3 and tmtaaH 2 , the macrocyclic ligand 6,8,15,17-tetramethyldibenzotetraaza[14]annulene, depending on the stoichiometry, solvent and temperature. The crystal structure of Ce(tmtaa) 2 is isostructural with Zr(tmtaa) 2 , however magnetic susceptibility measurements in the range 5-300 K show that Ce(tmtaa) 2 is not diamagnetic, but is a temperature-independent paramagnet (TIP), similar to Ce(cot) 2 , cerocene. 2 , and phthalacyanines, pcH 2 . Although all of these ligands form stable dianions, their electronic structure and therefore the electronic properties of their complexes are different. The tmtaa 2-is a 24 π-electron system (4nπ, n= 6) that is not Hückel aromatic. The negative charge is not delocalized over its entire framework, but is localized on the four nitrogen atoms, that carry a total negative charge of -0.98 e, and the two β-carbon atoms in the imidinate ring that carry a -0.24 e charge, NC α (Me)C β (H)C α (Me)N. 6,7 The tmaa 2-is therefore not planar but is saddle shaped with idealized C 2v symmetry. 8 The cot 2-(4nπ+2, n=2) and porph 2-(4nπ+2, n=6) are aromatic and the negative charge is delocalized over the planar rings. Pr, Nd, Sm, Gd, Tb, Er and Yb. 30 In this paper the synthesis and physical properties of Ce(tmtaa) 2 and related complexes are described. Results and Discussion Synthesis and StructureThe synthesis of the complexes involves the reaction of tmtaaH 2 with Ce[N(SiMe 3 ) 2 ] 3 in various molar ratios. Proton transfer reactions of Ce[N(SiMe 3 ) 2 ] 3 , the pK a of (Me 3 Si)NH in thf is 26, 31 depend critically on the solvent, concentration of the reactants, and temperature. These details are given in the Experimental Section, which are reproducable when close attention to detail is observed, and shown schematically in Scheme 1. Solutions of complexes Ce(tmtaa)(tmtaaH) (1) and Ce 2 tmtaa 3 (2) are extremely sensitive to trace amounts of air, which result in formation of Ce(tmtaa) 2 (3), which is stable to air and moisture. Deliberate oxidation of either 1 or 2 is therefore an excellent synthetic route to 3.Ce(tmtaa)(tmtaaH) (1) not when Ln = Ce. Crystals of Ce(tmtaa)(tmtaaH) grown from toluene, were twinned, the tmtaa and tmtaaH fragments are disordered, and therefore the X-ray diffraction pattern could not be resolved. However, the 2:1 stoichiometry of the complex is confirmed. Ce(tmtaa)(tmtaaH) (1) decomposes slowly to Ce(tmtaa) 2 (3) and tmtaaH 2 (ratio 1:1) in C 6 D 6 at 65 °C over 14 days. Close inspection of the decomposition process reveales that after one day small amounts of Ce 2 (tmtaa) 3 (2) and tmtaaH 2 are detected in the 1 H NMR spectrum. Over the time priod of two weeks the resonances due to 2 increase then decrease as 3 is formed and the resonances due to tmtaaH 2 continue to increase until a steady state is reached. The decomposition does not eliminate hydrogen since the latter is not observed in the 1 H NMR spectrum and the addition of dehydroanthracene does not yield anthracene. It seems reasonable to suggest that the initial decomposition step of 1 is the format...

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Section: Methodsmentioning

confidence: 99%

Synthesis and magnetic properties of cerium macrocyclic complexes with tetramethyldibenzotetraaza[14]annulene, tmtaaH2

2006

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“…[13] (1,4,8,tetraazacyclotetradecane)ZrCl 2 (6): Compound 3 (0.86 g, 2.3 mmol) was dissolved in 30 mL of THF and was rapidly added to a concentrated THF solution of ZrCl 2 (CH 2 SiMe 3 ) 2 (Et 2 O) 2 (1.10 g, 2.3 mmol). A reflux condenser was adapted and the reaction mixture was left under mild reflux.…”

Section: Acknowledgementmentioning

confidence: 99%

“…This type of ligand set is attractive to transition metal chemistry due to (i) the enhanced stability that a cyclic array presents, (ii) the flexibility to adopt different conformations and (iii) a macrocycle cavity size that forces the metal centres to sit above the plane of the donors leaving two adjacent coordination positions available at the metal coordination sphere [3]. In addition, and contrasting with azamacrocycles such as porphyrins or tetraazannulenes, saturated macrocycles are less prone to undesired secondary reactions [4]. The scarce number of diamido/diamine transition metal complexes derived from cyclam lies on the difficulty of its selective functionalisation.…”

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confidence: 99%

trans-Disubstituted diamido/diamine cyclam zirconium complexes

Munhá¹,

Alves²,

Maulide

et al. 2008

Inorganic Chemistry Communications

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“…The reasons for these excluded: Floriani observed transfer of alkyl groups from Zr IV to the imine carbon atoms of the macrocyclic bis(di-differences are unclear and point out the need for a more detailed understanding of the reactivity of paramagnetic iminato) ligand tmtaa. [18] Reproducibility of the activities is poor (see the different activities given for entries 1, 3, 7, non-d 0 systems 8, 9 in the table). We found that the time taken to prepare the catalyst mixture and the laboratory temperature had a Experimental Section significant influence, indicating that the catalyst is not very stable.…”

Section: Chromiummentioning

confidence: 99%

β-Diiminato Complexes of VIII and TiIII – Formation and Structure of Stable Paramagnetic Dialkylmetal Compounds

Budzelaar¹,

Oort

Orpen

1998

Eur. J. Inorg. Chem.

235

250

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Migratory Aptitude of the Zr-C Functionalities Bonded to a Macrocyclic Structure: Thermally- and Solvent-Assisted Intra- and Intermolecular Migrations in Dialkyl(dibenzotetramethyltetraazaannulene)zirconium(IV)

Cited by 86 publications

References 0 publications

Synthesis and magnetic properties of cerium macrocyclic complexes with tetramethyldibenzotetraaza[14]annulene, tmtaaH2

Synthesis and magnetic properties of cerium macrocyclic complexes with tetramethyldibenzotetraaza[14]annulene, tmtaaH2

trans-Disubstituted diamido/diamine cyclam zirconium complexes

β-Diiminato Complexes of VIII and TiIII – Formation and Structure of Stable Paramagnetic Dialkylmetal Compounds

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