Rhodium(I)‐α‐Phenylvinylfluorenyl Complexes: Synthesis, Characterization, and Evaluation as Initiators in the Stereospecific Polymerization of Phenylacetylene

Abstract

The synthesis, characterization and use, as initiators for phenylacetylene polymerizations, of three new rhodium(I)vinyl complexes containing fluorenyl functionality with fluorinefunctionalized phosphine ligands is described. Rh(nbd)(CPh= CFlu)P(4-FC 6 H 4 ) 3 , Rh(nbd)(CPh=CFlu)P(4-CF 3 C 6 H 4 ) 3 , and Rh(nbd)(CPh=CFlu)P[3,5-(CF 3 ) 2 C 6 H 3 ] 3 (nbd: 2,5-norbornadiene; Flu: fluorenyl) were prepared and isolated as discrete, orange compounds and were readily recrystallized yielding X-ray quality crystals. All complexes were characterized by a combination [a] Materials: n-Butyllithium (nBuLi, 1.6 M solution in hexane, Sigma-Aldrich), 9-[bromo(phenyl)methylene]-9H-fluorene, (C 12 H 8 )C=CPhBrEur.

Rh(I)(2,5-norbornadiene)(biphenyl)(tris(4-fluorophenyl)phosphine): Synthesis, Characterization, and Application as an Initiator in the Stereoregular (Co)Polymerization of Phenylacetylenes

“…However, in this instance, we were able to directly observe the 103 Rh signal which appears as a doublet, due to coupling with 31 P, centered around δ = −7699 ppm (536 ppm if referenced to Rh metal), Figure A. This is consistent with the 103 Rh chemical shifts we reported for the series of fluorenyl-functionalized Rh­(I) complexes shown in Figure , compound B , which had measured shifts spanning the range δ = −7861 to −7870 ppm . To verify this observation and confirm purity we conducted a complementary 2D 31 P- 103 Rh­{ 1 H} heteronuclear multiple quantum coherence (HMQC) experiment, Figure B.…”

“…Inspired by the work of Masuda and co-workers and the dearth of examples of well-defined Rh(I) species as initiators for PA (co)polymerization, we recently reported the synthesis and application of three new Masuda-type Rh(I)-α-phenylvinylfluorenyl complexes containing fluorine-functionalized phosphine ligands, Figure 1, compound B. 22 Surprisingly, while meeting the general structural requirements for highly efficient initiators, 11 these complexes exhibited IEs (as determined by SEC), for PA homopolymerization, in the range 0.13 to 0.56, although the product polymers possessed narrow molecular weight distributions and the expected high cis−transoidal stereoregularity. To more clearly understand the difference in IEs for complexes A and B, we subsequently targeted a new complex, Rh(I)(2,5-norbornadiene)(2-phenylnaphthyl)tris(4fluorophenyl) phosphine, a Rh(I)-aryl species.…”

Rh(I) Complexes in Catalysis: A Five-Year Trend

“…Comparable results were previously reported by the same research group with Rh(NBD)(l-proline) (NBD = 2,5-norbornadiene) on the same reaction [82], as [Rh(NBD)Cl] 2 is another common initiator for this kind of process. An analogous idea was behind the synthesis of novel Rh(NBD) vinyl complexes (Scheme 8) containing a fluorenyl moiety and different fluorine-functionalized triarylphosphines for the homopolymerization of unsubstituted phenylacetylene [83] (Figure 6). Such complexes produced highly stereoregular polyphenylacetylene with cis-transoidal configuration (cis contents as high as 96%).…”

Polymerizations Mediated by Well‐Defined Rhodium Complexes

“…Intrigued by the limited number of reported well‐defined Rh I ‐vinyl complexes that serve as initiators for the controlled polymerization of phenylacetylene, we recently reported three new Rh I ‐α‐phenylvinylfluorenyl species based on the Masuda structural motif, that is, Rh(nbd)(CPh=CFlu)P(X‐C 6 H 4 ) 3 (where X=4‐F, 4‐CF 3 , 3,5‐(CF 3 ) 2 ) . Figure shows the X‐ray crystal structure of the Rh(nbd)(CPh=CFlu)P(4‐FC 6 H 4 ) 3 complex.…”