Chelating N-pyrrolylphosphino-N′-arylaldimine ligands: synthesis, ligand behaviour and applications in catalysis

Abstract

Two families of variously-substituted N-pyrrolylphosphino-N'-arylaldimine ligands, 2-(aryl-N=CH)C4H3N-PR2 {R=Ph; R=Pri2N}, have been prepared from the corresponding pyrrolylaldimines . The donor characteristics/basicity of P-N-chelating and have been assessed using a combination of 31P{1H} NMR and IR spectroscopies through study of the magnitudes of 1JSeP for the phosphorus(V) selenides and , and measurement of nu(CO) for the complexes [RhCl(CO)(-kappa2-P,N)], respectively. The synthesis of the palladium(II) complexes [PdCl2(-kappa2-P,N)] was readily achieved from reaction of or with [PdCl2(MeCN)2] in CH2Cl2. X-Ray crystallographic studies of and confirm the chelating nature of the P-N ligands, which adopt a distorted 'envelope' conformation, and highlight the potentially significant steric demands of these metal scaffolds. Reaction of equimolar quantities of with [NiBr2(DME)] in MeCN afforded [NiBr2(-kappa2-P,N)], while the same reaction undertaken in CH2Cl2 with gave rise to the homoleptic bis(pyrrolatoimine) derivative [Ni{2-(mes-N=CH)C4H3N}2] in 45% yield, following P-N bond cleavage. Complex was characterised in the solid-state by X-ray crystallography. No identifiable metal-containing complexes could be obtained on reaction of with a variety of sources of Ni(II). The palladium dichloride complexes and proved inactive in combination with MAO or EtAlCl2 for ethylene polymerisation, and with methanesulfonic acid for CO/ethylene co-polymerisation. Contrastingly, the nickel complexes in combination with 4.5 eq. EtAlCl2 catalysed the formation of butenes and hexenes with moderate activity from ethylene at 1 bar.

Bis(2-{1-[(2,4,6-trimethylphenyl)imino]ethyl}pyrrol-1-ido-κ2N,N′)nickel(II): a supramolecular structure formed by C—H...π(arene) hydrogen bonds

“…These two ligands show an inverted arrangement with respect to one another. A similar trend was observed in several structures of analogous metal complexes (Anderson et al, 2006;Carabineiro et al, 2007;Imhof, 2012Imhof, , 2013 The pyrrole rings and the imine groups lie trans with respect to each other.…”

“…One of these studies focused on the syntheses of transition metal complexes with a variety of imine-pyrrole ligands (Mashima & Tsurugi, 2005). In the reported cases, most substituents at the iminic C atom of ISSN 2053ISSN -2296 # 2015 International Union of Crystallography the mono(imino)pyrrolyl unit were H atoms (Dawson et al, 2000;Anderson et al, 2006;Carabineiro et al, 2007;Pé rez-Puente et al, 2008;Imhof, 2012Imhof, , 2013. In the reported cases, most substituents at the iminic C atom of ISSN 2053ISSN -2296 # 2015 International Union of Crystallography the mono(imino)pyrrolyl unit were H atoms (Dawson et al, 2000;Anderson et al, 2006;Carabineiro et al, 2007;Pé rez-Puente et al, 2008;Imhof, 2012Imhof, , 2013.…”

Hydrosilylation in Aryliminopyrrolide‐Substituted Silanes

“…Anderson et al. have prepared a range of aryliminopyrrolide phosphines as P,N‐chelating ligands on Rh, Pd, and Ni complexes for olefin oligomerization, and Vránová et al. synthesized aryliminopyrrolyl antimony chloride .…”

A Truly Multifunctional Heterocycle: Iminophosphorane, N,P Chelate, and Dihydropyridine

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Bidentate ligands occupy a central position in coordination chemistry. Among such heteroditopic ligands, bidentate N,P chelates [2,3] are some of the most frequently used and have been shown to be beneficial in a number of applications such as allylic substitution, [4,5] olefin oligomerization, [6,7] and asymmetric hydrogenation. Among such heteroditopic ligands, bidentate N,P chelates [2,3] are some of the most frequently used and have been shown to be beneficial in a number of applications such as allylic substitution, [4,5] olefin oligomerization, [6,7] and asymmetric hydrogenation.

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“…[1] Their electronic and steric asymmetry can be harnessed to control reactivity at the chelated metal centre, often as a result of the differing trans influences exerted by the two donor components. Among such heteroditopic ligands, bidentate N,P chelates [2,3] are some of the most frequently used and have been shown to be beneficial in a number of applications such as allylic substitution, [4,5] olefin oligomerization, [6,7] and asymmetric hydrogenation. [8] In this context, we have previously reported the synthesis and coordination chemistry of the k 2 -N,P-chelating pyridyl-Nphosphinoimines I (Scheme 1).…”