Coordination Chemistry inside Polymeric Nanoreactors: Metal Migration and Cross-Exchange in Amphiphilic Core-Shell Polymer Latexes

Abstract

Abstract:A well-defined amphiphilic core-shell polymer functionalized with bis(p-methoxyphenylphosphino)phenylphosphine (BMOPPP) in the nanogel (NG) core has been obtained by a convergent RAFT polymerization in emulsion. This BMOPPP@NG and the previously-reported TPP@NG (TPP = triphenylphosphine) and core cross-linked micelles (L@CCM; L = TPP, BMOPPP) having a slightly different architecture were loaded with [Rh(acac)The interparticle metal migration from [Rh(acac)(CO)(TPP@NG)] to TPP@NG is fast at natural pH and much slower at high pH, the rate not depending significantly on the polymer architecture (CCM vs. NG). The cross-exchange using [Rh(acac)(CO)(BMOPPP@Pol)] and [RhCl(COD)(TPP@Pol)] (Pol = CCM or NG) as reagents at natural pH is also rapid (ca. 1 h), although slower than the equivalent homogeneous reaction on the molecular species (<5 min). On the other hand, the subsequent rearrangement of [Rh(acac)(CO)(TPP@Pol)] and [RhCl(COD)(TPP@Pol)] within the TPP@Pol core and of [Rh(acac)(CO)(BMOPPP@Pol)] and [RhCl(COD)(BMOPPP@Pol)] within the BMOPPP@Pol core, leading respectively to [RhCl(CO)(TPP@Pol) 2 ] and [RhCl(CO)(BMOPPP@Pol) 2 ], is much more rapid (<30 min) than on the corresponding homogeneous process with the molecular species (>24 h).

Triphenylphosphine‐Functionalized Core‐Cross‐Linked Micelles and Nanogels with a Polycationic Outer Shell: Synthesis and Application in Rhodium‐Catalyzed Biphasic Hydrogenations

“…Although relatively broad because of the increased correlation time in the polymeric environment, the Rh coupling is clearly discernible with J PRh ≈150 Hz, consistent with previous studies [6a, 7, 11a–c, 13] . These spectral parameters agree well with those reported for the molecular model (31.5 ppm, J =152 Hz) [14] and for the same complex anchored to the equivalent neutral‐shell polymer (29.3 ppm, J =150 Hz) [13] . The spectra for the Rh‐charged particles at higher P/Rh ratios (2:1 or 4:1) gave no observable signal because of further broadening by the rapid degenerative phosphine exchange, as previously described for the equivalent neutral‐shell polymers [13] …”

“…The free TPP resonance at −6.5 ppm was fully replaced by a doublet at 32.2 ppm assigned to the Rh‐coordinated TPP (e.g., see the spectra for the CCM 10 % particles in Figure 4). Although relatively broad because of the increased correlation time in the polymeric environment, the Rh coupling is clearly discernible with J PRh ≈150 Hz, consistent with previous studies [6a, 7, 11a–c, 13] . These spectral parameters agree well with those reported for the molecular model (31.5 ppm, J =152 Hz) [14] and for the same complex anchored to the equivalent neutral‐shell polymer (29.3 ppm, J =150 Hz) [13] .…”

“…[6a, 7, 11a-c, 13] These spectralp arameters agree well with those reported for the molecular model (31.5 ppm, J = 152 Hz) [14] and for the same complex anchored to the equivalent neutral-shell polymer (29.3 ppm, J = 150 Hz). [13] The spectra for the Rh-charged particles at higher P/Rh ratios (2:1 or 4:1) gave no observable signal because of furtherb roadening by the rapid degenera-tive phosphine exchange, as previously described fort he equivalent neutral-shell polymers. [13] In our previous work with the equivalent neutral-shell nanoreactors,t he 31 Ps ignal disappearance at higherP /Rh ratios could be used to demonstrate af ast metal migration between cores of different macromolecules.…”

“…Using the same protocol optimized in previous contributions, [11d, 13] complex [RhCl(COD)] 2 was introduced into the nanoreactor cores after pre‐swelling the polymer particles with toluene. Upon equilibrating the latex phase with a toluene solution of the metal complex under vigorous stirring at room temperature, the Rh complex was transferred into the nanoreactor cores quantitatively within 30 min, as optically assessed by the transfer of the complex orange color from the organic to the aqueous phase.…”

Phosphorus‐Containing Gradient (Block) Copolymers via RAFT Polymerization and Postpolymerization Modification

“…RAFT‐based synthesis of single‐chain nanoparticles, core cross‐linked micelles, porous networks, and soluble polymers bearing phosphine functionalities as polymeric supports for transition metal catalyzed organic transformations has received recent attention within the scientific community. A common monomer used in this context has been the commercially available phosphine‐functional styrenic 4‐(diphenylphosphino)styrene (DPPS), with several reports focusing on its copolymerization with other styrenic monomers . Surprisingly little focus has been given to the distribution of phosphine functionality along the polymer with these copolymers; the copolymerization behavior, including the reactivity ratios, of DPPS and styrene (St) has not yet been reported.…”