Air-Stable (Phenylbuta-1,3-diynyl)palladium(II) Complexes: Highly Active Initiators for Living Polymerization of Isocyanides

Abstract

A family of air-stable (phenylbuta-1,3-diynyl)palladium(II) complexes were designed and prepared in a facile synthetic procedure. Their structures were characterized by (1)H and (13)C NMR, MS, and X-ray analysis. These Pd complexes were revealed to efficiently initiate the polymerization of phenyl isocyanides in a living/controlled chain growth manner, which led to the formation of poly(phenyl isocyanide)s with controlled molecular weights and narrow molecular weight distributions. (13)C NMR analysis indicated the isolated poly(phenyl isocyanide) was of high stereoregularity. The Pd unit at the end of the polymer chain could undergo further copolymerization with phenyl isocyanide monomers to give block copolymers. It was also found that incorporation of an electron-donating group on the phenyl group of the Pd complex could improve the catalytic activities. Furthermore, these Pd complexes were tolerant to most organic solvents and applicable to a wide range of isocyanide monomers including alkyl and phenyl isocyanides and even phenyl isocyanide with bulky substituents at the ortho position and diisocyanide monomers. Therefore, this polymerization system is versatile in the preparation of well-defined polyisocyanides with controlled sequence. Bi- and trifunctional Pd complexes with two and three Pd units incorporated onto the same phenyl ring were designed and synthesized. They were also able to initiate the living polymerization of phenyl isocyanide to afford telechelic linear and star-shaped polyisocyanides with controlled molecular weights and narrow molecular weight distributions.

Silver‐Catalyzed Cross‐Coupling of Isocyanides and Active Methylene Compounds by a Radical Process

“…[24] Importantly,t he addition of either the radical scavenger TEMPO or BHT to the reaction mixture of 4a and 2a under an oxygen atmosphere resulted in an unidentified mixture,without formation of 5a,therefore suggesting af ree radical process.F urther, unlike H 2 Oa cting as the oxygen source in previous reports on isocyanideinvolved carbamoylation, [25] the reaction of 4a with 2a does not provided [ 18 O]-5a in the presence of H 2 18 O[ Eq. (5)]. Based on the results from the experimental investigations and related literature precedents,ap lausible reaction mechanism (Scheme 4) is proposed by using 2a as am odel substrate.I nt he radical initiation stage,t he carbonate anion of Ag 2 CO 3 abstracts ap roton from 2a,t hus leading to the generation of acarboanion and AgHCO 3 ,followed by further oxidation of ac arboanion by an Ag + ion to yield the radical intermediate A.…”

Versatile pH-response Micelles with High Cell-Penetrating Helical Diblock Copolymers for Photoacoustic Imaging Guided Synergistic Chemo-Photothermal Therapy

“…The block ratio of PPI and PCL was deduced to be approximately 1 to 1. After polymerization, in the 31 P NMR spectrum, the peak of the catalyst at δ 17.8 ppm was replaced by a new doublet at 14.7 ppm, which corresponded to the formation of the polymers (Figure 1C) 37. The FT-IR spectra of PM, ClPd(PEt 3 ) 2 (-RhB)-PCL, and PPI(-RhB)-OH samples showed a series of characteristic vibrations coming from both of PPI and PCL blocks (Figure S3).…”

“…The rhodamine-encoded bifunctional catalyst ClPd(PEt 3 ) 2 -RhB-OH bearing a Pd(II) active center and a hydroxyl group was synthesized from rhodamine B hydrochloride by sequential chemical modification (scheme S1a) 31, 33-35. The chemical structure of the intermediates (1-8) during the catalyst preparation were verified by 1 H NMR spectra, and the exact structure of the final ClPd(PEt 3 ) 2 -RhB-OH was confirmed by 1 H NMR, 13 C NMR, 31 P NMR, mass spectrometry (Figure S1), and FT-IR spectrometry (Figure S2).…”

Polypeptide‐b‐Poly(Phenyl Isocyanide) Hybrid Rod‐Rod Copolymers: One‐Pot Synthesis, Self‐Assembly, and Cell Imaging

“…[ 28,43,44 ] Chiral amino acid modifi ed rhodamine (RhB(D)) and pyrene (pyrene(D)) chromophores were synthesized according to reported procedures. [45][46][47] The synthetic procedures are shown in Scheme S1 and S2 in the Supporting Information, and the structures were confi rmed by 1 H NMR and mass spectroscopy, the results of which are shown in Figure S1, S2, S10, and S11 in the Supporting Information.…”