Palladium carbene complexes as persistent radicals

Abstract

A series of palladium(ii) persistent radical carbene complexes, [PC˙(sp2)P]PdX (X = Cl, Br, I), was synthesized from the nucleophilic carbene [PC(sp2)P]PdPMe3.

Non-heteroatom-substituted alkylidene complexes of groups 10 and 11

“…Thus, oxidation of the PMe3, ylid-like alkylidene complex 12a with Br2, I2 or with CH2X2 (X= Cl, Br, I) allowed the isolation of stable carbene radicals, 15a (Scheme 17). 45 The new, four-coordinate complexes are monomeric and exhibit solution magnetic moments close to 1.8 B. EPR measurements revealed g-factors close to 2, in accordance with the radical formulation proposed for the carbene ligand skeleton.…”

Formation of Palladium η2‐Bound Chalcogenoketones across a Pd+−C− Bond

“…Single‐crystal X‐ray diffraction was employed to investigate the molecular structure of 4 (Figure , Table ). The C−Pd distance of 2.098(3) Å is slightly elongated from previously reported C−Pd distances, while the tellurium atom is located 2.7132(3) Å away from the metal center, a slightly longer distance than in telluroethers bound to palladium (Table ) . The sum of angles about palladium (399.68°) along with the calculated τ ′ 4 =0.69 indicated a distorted tetrahedral geometry at the metal ( τ ′ 4 =0 for square planar and τ ′ 4 =1 for tetrahedral) .…”

“…1.21 Å), signifying the occurrence of π‐backbonding from the metal center. The C−Pd distance (2.176(3) Å) was also lengthened compared to values found in similar complexes . The 13 C NMR shift for the ketone carbon was observed as a broad singlet at 160.4 ppm, significantly upfield from the corresponding value in 2,2′‐bis(diphenylphosphino)benzophenone (196.8 ppm) .…”

“…We previously reported the synthesis and characterization of a nucleophilic carbene, [{PC(sp 2 )P}Pd(PMe 3 )] ( 1 , [PC(sp 3 )HP]=bis[2‐(diisopropylphosphino)‐phenyl]methyl, i Pr 2 P‐C 6 H 4 ‐CH‐C 6 H 4 ‐P i Pr 2 ) . Investigation of its reactivity brought to light the formation of the first nucleophilic palladium(II) radical carbene complex, [PC ⋅ (sp 2 )P]PdI, and the isolation of an adduct reminiscent of frustrated Lewis pairs . The latter was the consequence of a contributing resonance structure, in which the nucleophilic character was distributed through the phenyl ring adjacent to the carbene carbon.…”

Computation Sheds Insight into Iron Porphyrin Carbenes’ Electronic Structure, Formation, and N–H Insertion Reactivity

“…Figure S8present this result, confirming that Zhang and colleagues overlooked this crucial electronic structure. Furthermore, the claim of a C px radical finds precedent in de Bruin and others' work on cobalt porphyrin carbenes, 101,105,106 as well as work on oxidized iron porphyrin carbenes 107 and other systems 102,[108][109][110]. Furthermore, the claim of a C px radical finds precedent in de Bruin and others' work on cobalt porphyrin carbenes, 101,105,106 as well as work on oxidized iron porphyrin carbenes 107 and other systems 102,[108][109][110].…”