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Strained, Stable 2‐Aza‐1‐Phosphabicyclo[ n .1.0]alkane and ‐alkene Fe(CO) 4 Complexes with Dynamic Phosphinidene Behavior
Author(s) -
Borst Mark L. G.,
van der Riet Niels,
Lemmens Renske H.,
de Kanter Franciscus J. J.,
Schakel Marius,
Ehlers Andreas W.,
Mills Allison M.,
Lutz Martin,
Spek Anthony L.,
Lammertsma Koop
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200401249
Subject(s) - phosphinidene , bicyclic molecule , chemistry , intramolecular force , phenylacetylene , substituent , cycloaddition , alkene , stereochemistry , crystal structure , moiety , medicinal chemistry , crystallography , organic chemistry , catalysis
Abstract The synthesis of highly strained bicyclic phosphirane and phosphirene iron–tetracarbonyl complexes, that is, complexes with 2‐aza‐1‐phosphabicyclo[ n .1.0]alkanes and ‐alkenes ( n =3–5), is explored by using intramolecular cycloaddition of an in situ generated electrophilic phosphinidene complex, [R( i Pr)NPFe(CO) 4 ], to its CC‐ and CC‐containing R substituent. Saturated bicyclic complexes 7 a – c with n =4–2 are remarkably stable, as illustrated by the X‐ray crystal structure for 7 b ( n =3), yet all readily undergo retroaddition to react with phenylacetylene. Shuttling of the phosphinidene iron complex between two equivalent CC groups is demonstrated for a 1‐butene‐substituted 2‐aza‐1‐phosphabicyclo[3.1.0]hexane by selective 1 H NMR magnetization transfer from the phosphirane protons to the olefinic protons. Even the more strained unsaturated bicycles 17 a , b ( n =4,3) are surprisingly stable as illustrated by the X‐ray crystal structure for 17 a ( n =4), but the smaller phosphabicyclo[3.1.0]hex‐5‐ene ( 17 c , n =2) dimerizes to tricyclic 19 with a unique ten‐membered heterocyclic ring; an X‐ray crystal structure is reported. Like their saturated analogues also the bicyclic phosphirenes readily undergo retroaddition as shown by the reaction of their phosphinidene iron moiety with phenylacetylene.