Extending the Application Scope of Organophosphorus(V) Compounds in Palladium(II) Pincer Chemistry

Abstract

1-Dimethylthiocarbamoyloxy-3-diphenylphosphinobenzene was used as a key precursor for the synthesis of a whole series of organophosphorus(V) pincer ligands combining thiocarbamate donor group with PX coordination arm, where X = S, Se, O, NR (R = Ph, 4-NO 2 C 6 H 4 , COO t Bu, CH 2 Ph) or CHR′ (R′ = COOEt, CN). Direct cyclopalladation of the ligands obtained (used either as individual compounds or generated in situ in the reaction mixture) afforded hybrid pincer complexes with fiveand sixmembered fused metallacycles. In the case of phosphine sulfide and phosphine selenide derivatives, the cyclopalladation can readily be accomplished in CH 2 Cl 2 at room temperature, leading to the target pincer complexes in high yields. Their phosphine imide and phosphonium ylide counterparts can also be obtained under mild reaction conditions, but the yields strongly depend on the ligand stability (35−93%). Even in the case of the phosphoryl-functionalized ligand, the desired pincer-type complex was synthesized in ca. 15% yield, although the main direction of metalation was C(sp 3 )−H bond activation of one of the methyl groups in OC(S)NMe 2 moiety. Realization of κ 3 -S,C,X-coordination (X = S, Se, O, N, or C) in the resulting pincer complexes was unambiguously confirmed based on the multinuclear NMR ( 1 H, 13 C, 31 P, and 77 Se) and IR spectroscopic data. Comparative single-crystal XRD analyses allowed for outlining the main structural features of the palladacycles obtained depending on the nature of ancillary P(V)-donor group. In addition, the possibility of solid-phase cyclopalladation was demonstrated by the examples of phosphine chalcogenide and stable phosphine imide ligands. In most cases, this approach afforded the desired complexes with the same or even higher efficiencies than the conventional solution-based method. Preliminary investigations on the cytotoxic activity of some of the complexes obtained against several human cancer cell lines revealed the high activity of phosphine imide-based palladacycles, rendering further studies in this field promising.

NHC-Palladium(II) Mononuclear and Binuclear Complexes Containing Phenylene-Bridged Bis(thione) Ligands: Synthesis, Characterization, and Catalytic Activities

“…In complex 2a , the NHC planes tilt toward the center Pd coordination plane with dihedral angles of 62.3°. The Pd–C­(benzene) bond lengths of the Pd-NHC complexes are in the range of 2.0063–2.0461 Å and are consistent with Pd–C bond length values reported for palladium complexes with benzene-based pincer ECE ligands. − The C carbene –Pd­(1) bond lengths for 1b and 2a are 2.063(8) and 2.065(4) Å, respectively, both of which are slightly longer than that observed in complex 3b (2.022(8) Å) due to the weak coordination ability of the C carbene atom, which is validated by the 13 CS resonance results. The Pd–S bond lengths (2.279(3)–2.3374(10) Å) of the complexes are quite comparable to those of related Pd­(II) complexes reported. ,− …”

Synthesis, Photophysical Properties and Catalytic Activity of Ƙ3-SCS Pincer Palladium (II) Complex of N,N'-Di-Tert-Butylbenzene-1,3-Dicarbothioamide Supported by DFT Analysis

“…S13) in order to follow the subsequent reactions. However, in presence of K2CO3 as base, PdL + can be deprotonated at one of the two secondary amide sides and form neutral complex PdL [15,16,18,[56][57][58][59][60][61]. According to our calculation, the free energy of deprotonation of PdL + in DMF is found to be -36.7 kcal mol -1 .…”

Design of pincer complexes based on (methylsulfanyl)acetic/propionic acid amides with ancillary S‐ and N‐donors as potential catalysts and cytotoxic agents

“…In the case of the highly reactive hybrid bis(thioamide) derivative, the formation of pincer complex XXIII was observed even at room temperature [10a]. Not long ago the synthesis of an organometallic Pd(II) pincer complex XXIV was accomplished for the first time via CH bond activation of a bis(thiocarbamate) ligand with PdCl 2 (NCPh) 2 under mechanochemical conditions both by grinding of the reactants in a mortar and in a vibration ball mill at gram scale . Although solid‐phase synthesis has emerged as a useful tool in organic chemistry, the synthesis of organometallic and metal–organic compounds in the solid state is a relatively new and unexplored research area which has much room for development…”