Addition of Small Molecules to (η–C5H5)2Rh2(CO)(CF3C2CF3). 5.1 The Formation of Several Different Bridging Diene and Dienone Ligands by the Co-oligomerization of HC2-t-Bu with the Coordinated CF3C2CF3

Ron S. Dickson, Gary D. Fallon, Felicity I. McLure, Rhonda J. Nesbit

Research output: Contribution to journalArticlepeer-review

Abstract

Six products are obtained when (η–C5H5)2Rh2(CO)(CF3C2CF3) is treated with tert-butylacetylene at room temperature; another two are formed during workup of the reaction mixture. Two of the products are isomers of the bridging pentadienone complex (η-C5H5)2Rh2{C4(CF3)2H-t-BuCO}. In the major isomer 1 (10% yield), the configuration of the bridging ligand is -C(CF3)═C(CF3)C(O)C(H)═C(t-Bu)-; the reverse arrangement of H and t-Bu is indicated for the minor isomer 2 (5% yield). A metalladiene complex (η-C5H5)2Rh2{C4(CF3)2H-t-Bu} (3) is the major product (29% yield) of the reaction. Only one isomer is obtained, and it has the C(t-Bu) and C(H) carbons a and β, respectively, to the ring metal. This product is isolated only when the product mixture is chromatographed on “nonactivated” supports. With oven-dried supports, 3 is converted to a new complex of formula (η-C5H5)2Rh2{C4(CF3)2H-t-BuO2} (4). The structure of 4 has been determined from X-ray diffraction data; the bridging ligand is an unsaturated keto-ether of the type O═C(t-Bu)C(H)═C(CF3)OC(CF3)- which is attached to the Rh-Rh bond through the ketonic oxygen, the alkene bond, and the terminal (CF3)C: carbon. Another major product is formulated as (n-C5H5)2Rh2(CO){C4(CF3)2H-t-BuCO} (5) (17% yield). This complex contains a terminal carbonyl and a bridging cyclopentadienone ligand. Crystal structure determination establishes that the bridging ligand is bound to one rhodium by a cr-bond from a C(CF3) ring carbon and to the other rhodium by an η3-allyl attachment from C(CF3)═C(H)═C(t-Bu). Decarbonylation of this complex with Me3NO results in opening of the cylopentadienone ring to give complex 1. The final major product (19% yield) is (η-C5H5)2Rh2-(C2H-t-Bu){C4(CF3)2H-t-BuCO} (6). The molecular geometry of 6 has been determined by X-ray analysis. It has two bridging groups. One is a cyclopentadienone ligand which is η22-attached to the Rh-Rh bond; the other is a μ-η2-vinylidene group C=CH-t-Bu. This complex isomerizes during chromatography. The dicarbonyl complex (η-C5H5)2Rh2(CO)2(CF3C2CF3) (12% yield) is also a product of the reaction. Crystal data: complex 4, C20H20F6O2Rh2, triclinic, PĪ, a = 16.455 (8) Å, b = 13.836 (7) Å, c = 10.876 (5) Å, α = 115.09 (10)°, β= 98.64 (10)°, γ = 97.91 (10)°, Z = 4, final R = 0.052, Rw= 0.051 from 6915 observed reflections (12595 measured); complex 5, C22H20F6O2Rh2, monoclinic, P21/n, a = 14.590 (7) Å, b = 16.694 (8) Å, c = 9.407 (5) Å, β= 104.90 (10)°, Z = 4, final R = 0.054, Rw= 0.052 from 3472 reflections (6450 measured); complex 6, C27H30F6ORh2, orthorhombic, P212121, a = 16.283 (8) Å, b = 14.946 (7) Å, c = 10.571 (5) Å, Z = 4, final R = 0.060, Rw= 0.054 from 1739 reflections (4179 measured).

Original languageEnglish
Pages (from-to)215-223
Number of pages9
JournalOrganometallics
Volume6
Issue number2
DOIs
Publication statusPublished - 1 Feb 1987
Externally publishedYes

Fingerprint

Dive into the research topics of 'Addition of Small Molecules to (η–C5H5)2Rh2(CO)(CF3C2CF3). 5.1 The Formation of Several Different Bridging Diene and Dienone Ligands by the Co-oligomerization of HC2-t-Bu with the Coordinated CF3C2CF3'. Together they form a unique fingerprint.

Cite this