Pentamethyldiethylenetriamine complexation

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. ... 

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. 

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. 

Crassous et al.177) studied the polymerization of ethylene using n-butyllithium in conjunction with the tertiary diamines TMEDA, TEEDA (tetraethylethylenedi-amine) and PMDT (pentamethyldiethylenetriamine). In contrast to the situation with TMEDA the rate of polymerization was found to show a first order dependence upon the complexed chain end concentration. Steric hindrance seems to prevent the dimerization of the chain ends. Examination of the n-BuLi. TEEDA complex by -NMR shows that the displacement to high field of the protons a to the lithium induced by complexation is much smaller with TEEDA than with TMEDA or PMDT. With [TEEDA] < [RLi] time-averaged signals were obtained showing that the exchange process... 

Compounds 1 and 2 are monomeric species, probably owing to the large amount of steric bulk in the neighborhood of the lithium atom coordinating solvents [N,M, N, A/ -pentamethyldiethylenetriamine (PMDE-TA) in 1 and TMEDA and THE in 2] complex with lithium to complete its coordination sphere. The geometry about the lithium atom is nearly tetrahedral in both of these compounds. 

The first stannyl-alkali metal compound with a covalent Sn-M bond to be identified crystallographically was the pentamethyldiethylenetriamine (PMDETA) complex of Ph3SnLi (19-4), with rSnLi av. 281.7 pm, slightly greater than the sum of the two covalent radii (274 pm), and CSnC 96.1(2)°.30 This structure is preserved in solution, and, at -90 °C, the 7Li NMR spectrum shows (SnLi) = 412 Hz. Similarly the toluene complex... 

Two complexes containing a dilithiated stilbene fragment have been prepared and isolated from the reactions of 1,2-diphenylethane with N-chelated butyl-lithium reagents. " The molecular and crystal structures of these compounds, stilbene bis(lithium tetramethylethylenediamine) (Figure 4a) and stilbene bis(lithium pentamethyldiethylenetriamine) (Figure 4b), have been determined by X-ray diffraction techniques. Each structure contains two amine-solvated Li atoms located above and below the olefinic bond of a stilbene molecule. The stilbene molecule is planar in both structures, and is in a trans configuration about the C(7)—C(7 ) bond, which is ca. 0.01 nm longer than that in trans-stilbene. " The optical and "C n.m.r. spectra of THF solutions of the related dilithium and disodium salts of tetraphenylethylene dianion, as well as the spectra of their mixtures, have been examined. " The data can be rationalized in terms of the... 

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. 

Reactive carbon nucleophiles also include metalated metallocene and (arene)metal complexes. Equation 6 shows an example of the former treating the suspension of dUithoferrocene-tmeda conplex in Et20 with i-Pr2SiCl2 gave 3 in 34% yield.An example of the latter is shown in eq 7 conplex 4 was metalated with 2 equiv n-BuLi in the presence of pentamethyldiethylenetriamine (pmdta) in pentane, the dilithi-ated intermediate was isolated and then treated with i-Pr2SiCl2 in heptane to give complex 5. ... 

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... 

Fig. 2 Empirical general types of ate complex prepared via co-complexation (top) and an example of donor dependence on structural make-up (bottom) [13]. PMDETA=Af,Af,Af ,Af 2V -pentamethyldiethylenetriamine...

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