Synthesis, Characterization, and Catalytic Activity of Nickel(II) Alkyl Complexes Supported by Pyrrole–Diphosphine Ligands

Abstract

The organometallic Ni(II) chemistry of the pyrrole-based pincer ligands, (P 2 R Pyr) − (P 2 R Pyr = 2,5-(R 2 PCH 2 ) 2 C 4 H 2 N, R = Ph or Cy) is reported. Reactions of Grignard reagents with [NiCl(P 2 R Pyr)] afford a variety of alkyl and aryl complexes (methyl, ethyl, benzyl, phenyl, and allyl) that all display square planar geometries about nickel. The hydride complex, [NiH(P 2 Cy Pyr)], can also prepared either through treatment of [NiCl(P 2 Cy Pyr)] with LiHBEt 3 , or by reaction of H(P 2 R Pyr) with [Ni(COD) 2 ] (COD = 1,4-cyclooctadiene). Reactions of the methyl and hydride complexes with CO and CO 2 , respectively, evince clean migratory insertion chemistry of the Ni-C and Ni-H bonds. Both the alkyl and chloride complexes are active catalysts for the Kumada coupling of aryl chlorides and aryl or alkyl Grignard reagents at room temperature. The solid-state structures of several of the complexes are reported.

Carbonylative Coupling of Alkyl Zinc Reagents with Benzyl Bromides Catalyzed by a Nickel/NN2 Pincer Ligand Complex

“…[9] Many of these fast coupling reactions prove to be high yielding and function at near-ambient temperature.Aprominent feature of these reactions is the viability of sp 3 -derived building blocks,which are problematic components in the analogous plethora of palladium-catalyzed carbonylation reactions because of the inherent tendencyofpalladium alkyl complexes to undergo bhydride elimination. [10,11] We started our work by investigating as et of nickel(II) pincer complexes (NiL1-NiL3), [12][13][14][15] by 1 Ha nd 13 CNMR spectroscopy,f or their ability to mediate as equence of discrete reaction steps (Scheme 2). These steps consisted of transmetallation with an organometallic reagent (e.g.…”

“…These steps consisted of transmetallation with an organometallic reagent (e.g. propyl zinc bromide) followed by migratory insertion with 13 CO to produce an ickel-acyl species.E fficient transmetallation was observed in all three cases,but only the use of NiL3 led to the formation of as table acyl species,a si ndicated by as inglet resonating at d = 270.5 ppm in the 13 CNMR spectrum. Both NiL3 and the acyl species were found to be stable over ap rolonged period of exposure to excess 13 CO in THF (1 h, 30-50 8 8C).…”

New types of bi- and tri-dentate pyrrole-piperazine ligands and related zinc compounds: Synthesis, characterization, reaction study, and ring-opening polymerization of ε-caprolactone

“…1 of 83.95 (7) , much larger than the bidentate h 1 -terminal bonding mode of the pyrrole ring (vide infra). It is interesting to note that the two planes of the chelating rings and the Zn(1)-N(1)-Zn 0 (1)-N 0 (1) plane form a zigzag shape with the two chelating rings pointing in opposite directions, as shown in Fig.…”

“…CCDCC-995603 (1), CCDC-995604 (2), CCDC-995605 (3), CCDC-995606 (4), and CCDC-995607 (6) and CCDC-995608 (7). These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.…”

2,5‐Bis(2‐(diphenylphosphino)phenyl)‐1,3,4‐oxadiazole ligands and their Cu(I) complexes for Sonogashira coupling reaction

“…[19][20][21][22] For example, the combination of CuI and PPh 3 using potassium hydroxide [19] /potassium carbonate [20] as base has been used for the coupling of aryl iodides and terminal alkynes in water. [6,31] In view of diphosphane ligands and their metal complexes having been widely applied in catalytic chemistry for many years, [32][33][34][35] in this paper two diphosphane ligands containing nitrogen donor groups -2,5-bis(2′-(diphenylphosphino)phenyl)-1,3,4-oxadiazole (L1) and 2,5-bis(2-(diphenylphosphino)-5-methoxy)phenyl)-1,3,4oxadiazole (L2) and their binuclear Cu(I) complexes, L1Cu and L2Cuas their perchlorate salts, were synthesized and characterized. [29] Moreover, octahedral and rod-like CuI nanocrystals combined with PPh 3 have been used as catalysts for the cross-coupling reaction of 4-iodoanisole and phenylacetylene in the presence of K 2 CO 3 as base and PEG400 as solvent.…”