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

Abstract

The synthesis of the Rh(I)-aryl complex, Rh(I)(nbd)(BiPh)(P(4-FC 6 H 4 ) 3 ) is reported and its efficacy as an initiator for the (co)polymerization of phenylacetylenes established. The X-ray crystal structure indicates that the complex adopts a slightly distorted square planar geometry whose purity and structure was also confirmed by elemental analysis and 1 H, 13 C, 31 P, 19 F, 103 Rh, and 31 P-103 Rh{ 1 H} HMQC NMR spectroscopy. We demonstrate that Rh(I)(nbd)(BiPh)(P(4-FC 6 H 4 ) 3 ) mediates the (co)polymerization of phenylacetylenes in a controlled fashion with initiation efficiencies as high as 0.98, as evidenced by the pseudofirst-order kinetic and number-average molecular weight versus conversion profiles. The ability to form well-defined AB diblock copolymers, in a stereoregular manner, by sequential monomer addition is verified in the block copolymerization of phenylacetylene with 4fluorophenylacetylene with quantitative crossover efficiency, as determined by size exclusion chromatography.Letter pubs.acs.org/macroletters

(η4-Tetrafluorobenzobarrelene)-η1-((tri-4-fluorophenyl)phosphine)-η1-(2-phenylphenyl)rhodium(I): A Catalyst for the Living Polymerization of Phenylacetylenes

“…Rh(tfb)-(biph)(PAr 3 ) adopts a slightly distorted square-planar configuration, consistent with previously reported examples of structurally related rhodium(I)-vinyl and -aryl complexes. 21,25,27,31,38 The 1 H, 13 C, 19 F, and 31 P-103 Rh HMQC NMR spectra are given in the Supporting Information (chemical shifts are given in the Experimental Section) and are consistent with the experimentally obtained crystal structure. Figure 2 shows the 103 Rh{ 1 H, 31 P} and 31 P{ 1 H} NMR spectra of this new Rh(I)aryl complex.…”

“…21,25,27,31,38 The 1 H, 13 C, 19 F, and 31 P-103 Rh HMQC NMR spectra are given in the Supporting Information (chemical shifts are given in the Experimental Section) and are consistent with the experimentally obtained crystal structure. Figure 2 shows the 103 Rh{ 1 H, 31 P} and 31 P{ 1 H} NMR spectra of this new Rh(I)aryl complex. The 103 Rh{ 1 H, 31 P} spectrum shows a single, sharp signal at δ = −7674 ppm.…”

“…Figure 2 shows the 103 Rh{ 1 H, 31 P} and 31 P{ 1 H} NMR spectra of this new Rh(I)aryl complex. The 103 Rh{ 1 H, 31 P} spectrum shows a single, sharp signal at δ = −7674 ppm. This chemical shift value is consistent with our previously reported Rh(I)-vinyl and -aryl complexes, which spanned the range δ = −7699 to −7870 ppm.…”

“…Given the unexpected Rh-atom migrations resulting in at least two distinct species in solution, we subsequently prepared and evaluated Rh(nbd)(biph)(P(4-FC 6 H 4 ) 3 ) (biph = biphenyl). 31 While still likely susceptible to 1,4-Rh-atom migrations, the occurrence of such a migration would, in this instance, yield a structurally identical species. Following isolation, X-ray crystal structure analysis indicated a complex with the targeted structure which adopted a slightly distorted square-planar geometry, consistent with our previously reported Rh(I)-vinyl and -aryl complexes.…”

“…1 H and 13 C spectra were collected on a commercial broad-band probe, whereas the 103 Rh NMR was acquired at 19.1 MHz using a commercial 5 mm triple resonance broad-band probe (doubly tuned 1 H/ 31 P outer coil with inner broad-band coil) with 90°pulses of 27.5 and 18.4 μs for 103 Rh and 31 P, respectively. 103 Rh chemical shifts, δ, are given in ppm relative to Ξ = 3.186447 36 (the chemical shift for the commonly used reference Ξ = 3.160000 (Rh metal) is also given) by four-pulse 31 broadened by 10 Hz, and treated with spine-squared window function during processing. Coupling constants reported herein are given as absolute values but are likely to be negative in sign for 1 J Rh-P .…”