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Phosphinite Ligand Effects in Palladium( II )‐Catalysed Cycloisomerisation of 1,6‐Dienes: Bicyclo[3.2.0]heptanyl Diphosphinite (B[3.2.0]DPO) Ligands Exhibit Flexible Bite Angles, an Effect Derived from Conformational Changes ( exo ‐ or endo ‐Envelope) in the Bicyclic Ligand Scaffold
Author(s) -
Fairlamb Ian J. S.,
Grant Stephanie,
Tommasi Simona,
Lynam Jason M.,
Bandini Marco,
Dong Hao,
Lin Zhenyang,
Whitwood Adrian C.
Publication year - 2006
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.200600346
Subject(s) - chemistry , agostic interaction , phosphinite , cationic polymerization , ligand (biochemistry) , bicyclic molecule , bite angle , cyclopentene , stereochemistry , diene , medicinal chemistry , hydride , palladium , denticity , catalysis , regioselectivity , metal , polymer chemistry , organic chemistry , biochemistry , natural rubber , receptor
Changes in bidentate ligand structure significantly affect catalytic activity in mono‐cationic Pd(II)‐catalysed 1,6‐diene cycloisomerisation processes to give cyclopentene products. A bicyclo[3.2.0]heptanyl diphosphinite ligand (B[3.2.0]DPO, 3 ) is the first phosphorus‐based bidentate ligand capable of promoting regioselective 1,6‐diene cycloisomerisation. Trace quantities of water are essential for catalytic activity, as is the precise order of mixing of 1,6‐diene, Pd(II) pro‐catalyst and additives. Conformational changes in the ligand backbone seem to be important in stabilising the active catalyst species, assumed to be a cationic Pd(II) hydride species. DFT calculations support a change in bite angle on the cationic Pd(II) hydride species from circa 90° ( cis ) to 170° ( trans ); in the latter geometry an agostic interaction of the C4 endo hydrogen of the bicyclic ring‐system with Pd(II) stabilises the cationic metal centre. This unique ligand property could be exploited in other transition metal catalysed processes.