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A New Family of Mixed‐Valence Dinuclear Rhodium Complexes Containing the Two Metal Centers in Different Stereochemical Environments
Author(s) -
Herber Ulrich,
Pechmann Thomas,
Weberndörfer Birgit,
Ilg Kerstin,
Werner Helmut
Publication year - 2002
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 - 10.1002/1521-3765(20020104)8:1<309::aid-chem309>3.0.co;2-t
Subject(s) - chemistry , steric effects , rhodium , valence (chemistry) , chelation , ligand (biochemistry) , stereochemistry , medicinal chemistry , metal , catalysis , organic chemistry , receptor , biochemistry
A series of dinuclear chelate complexes of the general composition [Rh 2 ( κ 2 ‐L) 2 ( μ ‐CR 2 ) 2 ( μ ‐Sb i Pr 3 )] (R=Ph, p ‐Tol; L=CF 3 CO 2 − , acac − , acac‐f 3 − ) and [Rh 2 Cl( κ 2 ‐L)( μ ‐CR 2 ) 2 ( μ ‐Sb i Pr 3 )] (R=Ph, p ‐Tol; L=acac − , acac‐f 3 − ) has been prepared by replacement of the chloro ligands in the precursors [Rh 2 Cl 2 ( μ ‐CR 2 ) 2 ( μ ‐Sb i Pr 3 )] by anionic chelates. The lability of the Sb i Pr 3 bridge in the rhodium dimers is illustrated by the reactions of [Rh 2 ( κ 2 ‐acac) 2 ( μ ‐CR 2 ) 2 ( μ ‐Sb i Pr 3 )] ( 7, 8 ) with Lewis bases such as CO, CN t Bu, and SbEt 3 which lead to the formation of the substitution products [Rh 2 ( κ 2 ‐acac) 2 ( μ ‐CR 2 ) 2 ( μ ‐L′)] ( 13 – 16 ) in excellent yields. Treatment of 7 and 8 with sterically demanding tertiary phosphanes PR 3 (R 3 = i Pr 3 , i Pr 2 Ph, i PrPh 2 , Ph 3 ) affords the mixed‐valence Rh 0 –Rh II complexes [( κ 2 ‐acac) 2 Rh( μ ‐CPh 2 ) 2 Rh(PR 3 )] ( 21 – 24 ) and [( κ 2 ‐acac) 2 Rh{ μ ‐C( p ‐Tol) 2 } 2 Rh(P i Pr 3 )] ( 25 ) for which there is no precedence. The terminal P i Pr 3 ligand of 21 is easily displaced by alkynes, CN t Bu, and CO to give, by preserving the {( κ 2 ‐acac) 2 Rh( μ ‐CPh 2 ) 2 Rh} molecular core, the related dinuclear compounds 26 – 31 in which the coordination number of the Rh 0 center is 3, 4, or 5. The molecular structures of [Rh 2 Cl( κ 2 ‐acac)( μ ‐CPh 2 ) 2 ( μ ‐Sb i Pr 3 )] ( 5 ), [Rh 2 ( κ 2 ‐acac) 2 ( μ ‐CPh 2 ) 2 ( μ ‐CO)] ( 13 ), [( κ 2 ‐acac) 2 Rh( μ ‐CPh 2 ) 2 Rh(P i Pr 3 )] ( 21 ), and [( κ 2 ‐acac) 2 Rh( μ ‐CPh 2 ) 2 Rh(CN t Bu) 2 ] ( 30 ) have been determined crystallographically.