1,1,4,7,7-Pentamethyldiethylenetriamine, ligand

Certain multidentate ligands also provide for better solubility. Cu1 complexes formed with tctramcthylcthylcncdiaminc (TMEDA), N,N,N ,N ,N -pentamethyldiethylenetriamine (PMDETA, 140) and 1,1,4,7,10,10-hcxamethyltricthylcnctctraminc (HMTETA, 144) and Mc6TREN (145) have been found effective.311 Transfer to ligand during MMA polymerization has been reported as a side reaction when PMDETA is used. 12 313... 

In the presence of N,N,N, N",N"-pentamethyldiethylenetriamine ( = PMDETA), monomeric lithium complexes of bulky formamidinate ligands can be isolated. The compounds (Scheme 12) comprise a Li(PMDETA) center coordinated by a bulky formamidinate in either the E-syn- or E-anti-isomeric form. Two of the structures display coordination of the pendant amidinate imine, and can therefore be considered the first examples of if. r -C = N,N metal amidinate coordination. ... 

TMEDA changes into the dimeric [PhLi(TMEDA)]2. Monomeric phenyllithium PhLi(PMDTA) is observed if the tridentate donor ligand PMDTA (PMDTA = N,N,N, N, N"-Pentamethyldiethylenetriamine) is utilized.13... 

The reaction (a Schlenk dimerization) between the phosphine-borane-substituted alkene nPr2P(BH3) (Me3Si)C=CH2 and elemental lithium in THF yields the complex [(pmdeta)Li Prn2P(BH3) (Me3Si)CCH2]2 123 which in the solid state has a lithium bound to the BH3 hydrogens of the ligand, and no Li-C(carbanion) contact (pmdeta = N,N,N, N",N"-pentamethyldiethylenetriamine).85... 

Another system that has been investigated by C CP/MAS NMR spectroscopy as a function of different ligands is a-(dimethylamino)benzyllithium (2, Scheme 1) . The DEE complex was proven to exist in the solid state as an rf coordinated dimer . All the studied complexes are of an tf type according to comparison to solution NMR data. However, the actual structure varies as reflected by the shift difference between the two orf/zo-carbons. This difference ranges from 4.4 ppm for the N, N, N, N, N"-pentamethyldiethylenetriamine (PMDTA) complex to 20.3 ppm for the TMEDA complex. 

Data acquired at ambient temperature. Ligand abbreviations diglyme = bis(2-methoxyethyl) ether tmeda = tetramethylethylenediamine pmdta = pentamethyldiethylenetriamine teed = tetraethylethylenediamine OAr =... 

The dimethylaurate(I) anion was more readily isolated (9) when the lithium ion was complexed with pentamethyldiethylenetriamine (PMDT) [Eq. (2)]. The greater thermal stability of these complexes compared with their phosphine analogs was explained in terms of less-ready ligand dissociation and complexation of the lithium ion, preventing its attack at the gold center. 

Several ligands were used with allyl-type and vinyl-type initiators, such as 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMDETA), NJJyN JJ jN -pentamethyldiethylenetriamine (PMDETA), or compound 7 in Scheme 66. Zeng et al. showed that the combination of initiator 1 in Scheme 66 with BA6TREN or initiator 4 in Scheme 66 with BA6TREN gave the best control of the molar mass for the ATRP of 2-(dimethylamino)ethyl methacrylate. These allylic macromonomers are then able to copolymerize with acrylamide. 

Styrene (S, 99%, stabilized), 2-ethylhexylaciylate (EHA, 99-i-%, stabilized), copper(l) cUoride (CuCl), copper(l) bromide (CuBr, 98%) and ethyl-2-bromopropionate (99%) were purchased from Acros. 2-Bromopropionyl bromide (97%), ethylene glycol (99%), l,l,l-tris(hydroxymethyl)propane (97%), pentaerythritol (99%), 2,2 -bipyridine (bpyr, 99 +%) and N,N,N, N",N -pentamethyldiethylenetriamine (PMDETA, 99 %) were purchased from Aldrich. Tris(2-(dimethylamino)ethyl) amine (Mce-TREN) (18-19) and alkylated linear amine ligands (ALAL) (20-22) were synthesized according to literature procedures. All other solvents and chemicals were reagent grade, and were used as received. 

Cd. Cadmium perchlorate was found to catalyze allylation reactions using allyltributyltin in aqueous media very efficiently. These cadmium-catalyzed allylation reactions are accelerated by ligands such as N, N, N, N", A/ "-pentamethyldiethylenetriamine or 2,9-dimethylphenanthroline (Eq. 8.75). This accelerated the catalytic system to give allylation products of various aldehydes and ketones in high yields. 

Typically, phosphoms-based ligands are used to complex no-copper transition metals. Whereas, nitrogen-containing ligands have been used in copper-and iron-mediated ATRP, including 1,1,4,7,10,10-Hexamethyltriethylenetetramine (HMTETA), 2,2 -bipyridine (Bipy), NJ l,N d l ,N -pentamethyldiethylenetriamine (PMDETA), and tris[2-(dimethylamino)ethyl]amine (MceTREN) [26, 27], The activation rate constants for these ligands in copper bromide mediated ATRP and the proposed reaction mechanism of copper/2,2 -bipyridine are shown in Fig. 3.5. 

The ligand effects in the formation of tertiary carbanions from substituted tertiary aromatic amides have been investigated." Reaction of 2-isopropyl-(iVA -diisopropyl)-benzamide (10) with f-BuLi in ether resulted in ortho deprotonation and the formation of a hemisolvate based on a tetranuclear dimer of (10-Li )2 Et2O (Scheme 7). Reaction of (10) with f-BuLi in the presence of the tridentate Lewis base NjNjN pentamethyldiethylenetriamine (PMDTA) or tridentate diglyme (DOME) takes a different course (Scheme 7). The soUd-state structures revealed a dimer core in which the amide oxygen atoms fail to stabilize the metal ions for the former case and a remarkable benzylic deprotonation giving the tertiary benzyllithium (lO-Li )-PMDTA for the latter. 

Problem 11,6 Styrene (St) was polymerized by ATRP using a copper(I) bromide (CuBr) catalyst, com-plexed with A, A, A, A, iV"-pentamethyldiethylenetriamine (PMDETA) ligand, and methyl 2-bromopropion-ate (MBrP) as initiator. Experiments were performed in 1 E mixed vessel at 110°C with excellent temperature control using a monomer to solvent (toluene) ratio of 70 30 wt% and molar ratios of 50 1 1 1 for St/MBrP/CuBr/PMDETA. Under these reaction conditions, only a portion of the catalyst species was soluble and 90% monomer conversion was obtained in 6 h. Calculate a theoretical molecular weight (MW) of the polymer obtained. How would you explain if the experimental MW is found to be higher than the theoretical... 

Yousef RI, Walfort B, Rtiffer T, Wagner C, Schmidt H, Herzog R, Steinbom D (2005) Synthesis, characterization and Schlenk equilibrium studies of methylmagnesium compounds with O- and N-donor ligands— the unexpected behavior of [MgMeBr(pmdta)] (pmdta = N,N, N ,N ,N -pentamethyldiethylenetriamine). J Organomet Chem 690 1178—1191... 

Figure 12 illustrates that while the Cu7N,N,N, N", N"-pentamethyldiethylenetriamine (PMDETA) complex is active, it disproportionates in aqueous ATRP. On the other hand, ligands such as bpy, HMTETA, and TPMA can be used in aqueous media, although with rather different activities. If necessary, catalyst disproportionation in water can be suppressed by using an appropriate cosolvent or by addition of a pseudoligand that will stabilize Cu versus Cu , such as pyridine, which allows... 

Monomeric lithium enolates were rarely characterized by crystal structure analysis. It seems that prerequisite to monomer formation is an optimal solvation of the counterion lithium only if the metal is satisfied by a threefold, strong coordination by an external cosolvent, a monomeric enolate was detectable in the crystal state. This is illustrated by a crystal structure of the lithium enolate of dibenzyl ketone grown from a THF/diethyl ether solution containing the tri-dentate amine ligand A/ M M M" M"-pentamethyldiethylenetriamine (PMDTA), shown in Figure 3.4 [16a]. 

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