Ethylene Tri- and Tetramerization: a Steric Parameter Selectivity Switch from X-ray Crystallography and Computational Analysis

Abstract

A steric parameter (θN-sub) is introduced to describe the steric bulk at the nitrogen atom on a range of PNP ligands used in ethylene tri- and tetramerization. This parameter was calculated for the free ligands and different metal complexes thereof and compared to catalytic data. A specific tendency is observed for the value of θN-sub and 1-hexene selectivity, and a slight increase in 1-octene selectivity is found with increased bulkiness of the substituents on the nitrogen atom.

N,N-Bis(diphenylphosphanyl)cyclobutanamine

“…Diphosphinoamine (PNP) and other P donor ligands (Muller et al, 2008;Purcell et al, 1995;Otto et al, 2005;Otto & Roodt, 2001) with various substituents on both the P and N atoms form part of ongoing research in different catalytic olefin transformation reactions such as hydroformylation (Haumann et al, 2004;Crous et al, 2005), metathesis (Booyens et al) methoxycarbonylation (Ferreira et al, 2007) and tetramerization (Cloete et al, 2011). In the title compound, C 29 H 29 NP 2 , Fig.1, all bond distances and angles fall within the range for similar complexes (Keat et al, 1981;Cotton et al, 1996;Fei et al, 2003;Cloete et al, 2008Cloete et al, , 2009Cloete et al, , 2010Engelbrecht et al, 2010aEngelbrecht et al, , 2010b.…”

“…For diphosphinoamine (PNP) and other P-donor ligands, see: Muller et al (2008); Purcell et al (1995); Otto & Roodt (2001); Otto et al (2005). For their use in catalytic olefin transformation reactions, see: Haumann et al (2004); Crous et al (2005); Booyens et al (2007); Cloete et al (2011); Ferreira et al (2007).…”

Crystal structure of dichlorido(N-o-tolyl-1,1-di-p-tolylphosphanamine–κ1 P)-(methoxydi-p-tolylphosphane-κ1 P)palladium(II), C36H39Cl2NOP2Pd

“…Palladium(II) complexes containing phosphine and nitrogen donor atoms have been extensively utilized in various catalytic reactions such as the Buchwald-Hartwig and Suzuki cross coupling reactions [6][7][8][9][10][11]. The success of such ligands owes it to the fact that both the steric and the electronic properties of the donor groups can be easily altered to develop new highly effective catalysts [10].…”

“…The success of such ligands owes it to the fact that both the steric and the electronic properties of the donor groups can be easily altered to develop new highly effective catalysts [10]. More recently, attention has been directed towards designing chelating ligands such as diphosphinoamine (P-N-P) with easily tunable peripheries [11]. Unlike the hit-and-run/combinatorial approach often adopted due to various reasons, the approach described herein involves critical stepwise ligand design strategy.…”

Alloyed Tetranuclear Metal Chains of Pd4−nPtn (n=0–3) Scaffolded by a New Linear Tetraphosphine Containing a PNP Bridge

“…We have then intended to design Ph 2 PCH 2 P(Ph)N(R)P(Ph)CH 2 PPh 2 type linear tetraphosphines because the centralN Rg roup is easily varied by commercially availableprimary amines,and enablesb oth steric and electronic tuning of the central part of linear tetraphosphines.W hereas many phosphazane compounds formulated R 2 PN(R')PR 2 have been used to synthesize mono-, di-, andt rinuclearc omplexes with some functionalities concerning to the NR' substituents, [8][9][10][11][12][13][14][15][16][17][18] multidentate linear phosphine ligands with PNP bridgesa re no longer synthesized so far,e xcept some phosphazane macrocyclic ligands. [19] In the present study,anew linear tetraphosphine containing aP N(Ph)P phosphazane bridge, rac-bis[(diphenylphosphinomethyl)phenylphosphino]phenylamine (rac-dpmppan),w as synthesized and effectively utilized to stabilize as eries of Pd/Pt mixed metal tetranuclear chains, [Pd 4Àn Pt n (m-racdpmppan) 2 (XylNC) 2 ](PF 6 ) 2 (XylNC = xylyl isocyanide; n = 0: Pd 4 (1), 1: PtPd 3 (2), 2: PtPd 2 Pt (3), 2: Pt 2 Pd 2 (4), 3: Pt 2 PdPt (5)), in which the number and positionso fa dditional Pt atoms were remarkably controlled, and their electronic structures are finely tuned as alloyed metal chains by atomically precise Pt incorporation.…”