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Reactions of co-ordinated ligands. Part 23. Metalla-ring-forming reactions between hexafluoroacetone and η 4 -1,3-diene(η 5 -indenyl)rhodium complexes; the crystal and molecular structures of [Rh{OC(CF 3 ) 2 CH 2 C(Me)CHCH 2 }(η 5 -C 9 H 7 )] and [Rh{OC(CF 3 ) 2 C 3 H 3 C 6 H 4 }(η 4 -trans-C 4 H 4 Me 2 -1,4)]

1981; Royal Society of Chemistry; Issue: 2 Linguagem: Inglês

10.1039/dt9810000400

2050-5671

Peter Caddy, Michael Green, Judith A. K. Howard, Jacqueline M. Squire, Nicholas J. White,

Fluorine in Organic Chemistry

Reaction (room temperature) of hexafluoroacetone with isoprene- or 2,3-dimethylbuta-1,3-diene-(η5-indenyl)-rhodium affords respectively the η3-allylic rhodium(III) complexes [[graphic omitted](R2)CH2}(η5-C9H7)](1a; R1= Me, R2= H), (1b; R1= H, R2= Me)(ratio 5 : 1), and (2; R1= R2= Me). A single-crystal X-ray diffraction study of (1a) showed that the crystals are monoclinic, space group P21/a, with Z= 4 in a unit cell of dimensions a= 14.020(7), b= 8.690(4), c= 14.669(5)Å, and β= 101.61(3)°. The structure has been solved by heavy-atom methods from automated diffractometer data, and refined to R 0.045 (R′ 0.056) for 2 704 reflections. The rhodium adopts an essentially octahedral geometry arising from η5 bonding of an indenyl ligand, a η3-allylic group formed from linking of the isoprene to the hexafluoroacetone, and a rhodium–oxygen σ bond. trans,trans-Hexa-2,4-diene(η5-indenyl)rhodium reacts with hexafluoroacetone via a different reaction path to form the rhodium(I) complex (3). A single-crystal X-ray diffraction study of (3), a tris olefin complex, showed that the crystals are monoclinic, space group P21/c with Z= 4 in a unit cell of dimensions a= 8.094(2), b= 16.962(8), c= 12.782(4)Å, and β= 99.81 (2)°. The structure has been refined to R 0.021 (R′ 0.025) for 2 878 reflections. The rhodium adopts an essentially square-planar configuration the co-ordination sites being occupied by a η4-bonded trans,trans-hexa-2,4-diene, a η2-bonded indenyl ligand, and an oxygen atom of the hexafluoroacetone molecule σ bonded to rhodium. The hexafluoroacetone is bonded to the C5 ring of the indenyl ligand. The mechanism of formation of these complexes is discussed. In contrast, hexafluoroacetone reacts with bis(ethylene)(η5-indenyl)rhodium to form ethyl(hexafluoroacetylacetonato)(η5-indenyl)rhodium.