Ligands with an NPNPN-framework and their application in chromium catalysed ethene tri-/tetramerization

Abstract

Novel Cr(iii) catalysts supported by linear phosph(iii)azanes of the type R(1)R(2)N-P(Ph)-NR(3)-P(Ph)-NR(4)R(5) have been prepared, all of which, upon activation with MMAO-3A, are highly active for ethene tri-/tetramerization with considerable selectivity. The effect of ligand substitution as well as solvent on the catalytic performance has been examined.

Selective Reductions of N,N‐Bis{chloro(aryl)‐phosphino}‐amines Yielding Three‐, Five‐, Six‐, and Eight‐Membered Cyclic Azaphosphanes

“…The lone electron pair at the R phosphorus center stands syn to the central N−C bond axis whereas the lone pair of the S center is in the anti position. Unlike compound 1 a , the geometry at the nitrogen of 1 b is almost perfectly planar (∑(∢N1)=359.86°), which is in good agreement with the comparable (R 1 R 2 )N‐P(R 3 )‐N(R 1 )‐P(R 3 )‐N(R 2 R 1 ) compounds published by Peulecke et al …”

“…The lone electron pair at the R phosphorus centers tands syn to the central NÀC bond axis whereas the lone pair of the S centeri si nt he anti position. Unlike compound 1a,t he geometry at the nitrogen of 1b is almost perfectly planar( AE(aN1) = 359.868), which is in good agreement with the comparable (R 1 R 2 )N-P(R 3 )-N(R 1 )-P(R 3 )-N(R 2 R 1 )c ompounds published by Peulecke et al [12] In comparison to compound 1a,t he P1-N1-P2 angle (120.52 (6)8)i sc learly widened. Both PÀNb ond lengths (P1À N1 = 1.693(1) ,P 2 ÀN1 = 1.6989 (10) )a re in the same range as compound 1a.F urthermore, the stericd emanda tt he phosphorusa toms was increased by using 2,4,6-tris(isopropyl)phenyl (TiPP) substituents.…”

“…The molecular structure of 1 c corresponds to the R , R / S , S isomer (Figure ). Interestingly, it possesses an unusual conformation when the setting of the PR 2 substituents to each other is regarded along the PP axis: in contrast to other (R 1 )(R 2 )P‐N(R 3 )‐P(R 2 )(R 1 ) compounds, the substituents at the phosphorus centers (R 1 ) and (R 2 ) are neither syn (Scheme (a), i.e., compound 1 a ) nor anti (Scheme (b), i.e., compound 1 b ), but can be best described as semi‐gauche to each other, which might be an effect of the large TiPP substituents.…”

PNPN‐H in Comparison to other PNP, PNPN and NPNPN Ligands for the Chromium Catalyzed Selective Ethylene Oligomerization

“…Linear phosph(III)azanes of the type R 1 R 2 N−P(Ph)‐NR 3 ‐P(Ph)‐NR 4 R 5 were known, but their use in catalytic ethylene oligomerization had not been studied before. The N ‐phosphinoamide ligands were obtained by aminolysis with primary or secondary amines or by salt metathesis of the in situ‐ generated lithium amides and the corresponding dichloroaminophosphines (Scheme ) …”

Chromium Complexes Supported by Phenyl Ether‐Pyrazolyl [N,O] Ligands as Catalysts for the Oligo‐ and Polymerization of Ethylene

“…[ 13–16 ] In this way, significant efforts have been dedicated to the synthesis of new families of ligands based on a wide variety of donor‐group combinations aiming to generate more efficient chromium catalyst systems that are capable of selectively forming α‐olefins with high productivities. [ 17–81 ] In particular, chromium catalysts stabilized by pyrazolyl‐based tridentate ligands have been successfully synthetized and their catalytic application in ethylene oligomerization explored in details. [ 51,81–91 ] Selected examples are presented in Chart 1.…”