Palladium co-ordination chemistry of β-diimines: a preparative and structural comparison with α-diimines

Integrating Catalyst and Co‐Catalyst Design in Olefin Polymerization Catalysis: Transferable Dianionic Ligands for the Activation of Late Transition Metal Polymerization Catalysts

“…In addition, the C À C and C=N bonds within the nitrogen ligand fragment of the latter compounds are typical for a-diimine complexes. [12][13][14] Thus, it can be safely concluded that the structure of these catecholate complexes is appropriately described by the conventional catecholate(À2) representation (A) given in Figure 4.…”

“…Catecholates are usually considered weak field ligands, [11] and the comparison of the averaged M À N bond length in 2'b (1.984 ) with those in related square planar complexes PdL 2 (a-diimine) displaying the same N,N'-bis-(2,6-diisopropylphenyl)diimine ligand appear to confirm this notion. Thus, the dicationic complex with L = MeCN [12] exhibits an almost identical average MÀN distance (1.985 ), while this is shorter in neutral compounds with L = chloride (2.013 ) [13] and methyl (2.139 ). [14] Assuming that the field strength of s-ligands is directly related to their donor capability (and hence their trans influence), this trend indicates that the donor strength of tetrachlorocatecholate is very low, comparable to that of acetonitrile.…”

“…Their 1 H NMR spectra are simple and consistent with the highly symmetric structures proposed in Scheme 2, but scarcely informative. The 13 C NMR signals of the catecholate ligand are difficult to observe, as they lack any NOE enhancement and are broadened by the quadrupolar moment of the chlorine atoms, but they have been detected for the four complexes. For all of the four complexes, three catecholate resonances are observed: one at low field (d = 158-159 ppm), due to the oxygen-bound C atoms and two at ca.…”

“…NMR spectra were obtained on Bruker Avance DRX 400 (400 MHz) and Brucker Avance 300 (300 MHz) spectrometers. The 1 H and 13 …”

Structures and Reactions of 1,3‐Diamidodilithium Complexes: the Hemisolvated l‐[CMe2{CHMeN(R)}2Li2·OEt2], the Unsolvated 1:1 Mixed Organo‐amidolithium u‐[CMe2{CHMeN(R′)}2·Li2·(nBuLi)2], and the Product of Oxidative Ring Closure, the Pyrazolidine l‐[(RNCHMe)2CMe2] (R = 2‐iPr‐C6H4; R′ = 2,6‐iPr2‐C6H3)

“…The parent 1,3-diimines from which 1 is derived do not undergo similar carbolithiation or carbozincation reactivity. [14] Included in the previous examples of stacked diamidolithium structures is a case involving a 1,3-diamine linkage: [Li{Me 3 SiN(CH 2 ) 3 NSiMe 3 }Li] 2 was obtained as an unsolvated stack, reminiscent of the 1,2 cases discussed above. [8b] Complex 1 differs from all of these cases in the fact that it precipitates as an insoluble (presumably polymeric) powder from hexane.…”