Isomeric Preference in Complexes of Palladium(II) with Chelating P,N‐Donor Ligands

Abstract

Square-planar complexes [PdCl{κ 2 -(RN = CHC 6 H 4 PPh 2 )RЈ}] (RЈ = Cl; R = 4-CH 3 C 6 H 4 , 1a; R = 2-CH 3 OC 6 H 4 , 1b; R = 2-HOC 6 H 4 , 1c; RЈ = CH 3 ; R = 4-CH 3 C 6 H 4 , 2a; R = 2-CH 3 OC 6 H 4 , 2b; R = 2-HOC 6 H 4 , 2c) have been prepared and characterized. In complexes 2a-c only formation of one isomer was observed. The Pd-methyl bond arranges in a cis position to the phosphane fragment of the P,N chelating ligand. Reaction of complexes 2a-c in acetonitrile with AgBF 4 led to removal of the chlorido ligand and coordination of acetonitrile

Amidophosphine‐stabilized palladium complexes catalyse Suzuki–Miyaura cross‐couplings in aqueous media

“…The Pd1‐P1 bond distance in 7 of 2.2522(10) Å is similar to those observed in phosphine and phosphite complexes of Pd(II) (2.2–2.4 Å) and in neutral complex 1 (2.2543(9) Å) . The value of Pd1‐N1 bond length being 2.097(3) Å defines a strong coordination of N to Pd atom and is comparable to those found in similar monomeric N‐coordinated Pd complexes (2.073–2.155 Å) . The second nitrogen atom N2 of L 1 PPh 2 is protonated providing palladium cation cis ‐{[2‐(Me 2 NHCH 2 )‐6‐(Me 2 NCH 2 )C 6 H 3 ]Ph 2 P}PdCl 2 , that is compensated by Cl − anion.…”

“…The cis atoms define angles of P1-Pd1-N1 = 94.14 (12)°and Cl1-Pd1-Cl2 = 87.32(4)°, and there is a distortion of ideal square-planar geometry resulting from the ring strain of the six-membered metallacycle Pd1-P1-C1-C2-C7-N1. The Pd1-P1 bond distance in 7 of 2.2522(10) Å is similar to those observed in phosphine and phosphite complexes of Pd(II) (2.2-2.4 Å) [36][37][38][39][40][41][42][43][44][45][46][47][48][49] and in neutral complex 1 (2.2543(9) Å). [25] The value of Pd1-N1 bond length being 2.097(3) Å defines a strong coordination of N to Pd atom and is comparable to those found in similar monomeric N-coordinated Pd complexes (2.073-2.155 Å).…”

New Chiral P-N Ligands for the Regio- and Stereoselective Pd-Catalyzed Dimerization of Styrene

“…The downfield shifted 31 P signals for complex 2a and the J P-CH3 values suggested that the major species was the cis isomer. This was in agreement with the complex electronic pattern: chlorido was trans to the better donor atom (phosphorus), while methyl was trans to the poorer donor (nitrogen) (Figure 2) [38] and the groups having the highest trans influence were cis to each other. In agreement with this signal to proton assignment, the doublet of the methyl group in the cis isomer was remarkably upfield shifted with respect to the same signal in the trans isomer indicating that it fell into the shielding cone of the phenyl ring bound to phosphorus.…”

“…Interestingly, depending on the nature of the P-N ligand, the 31 P-NMR signals of the complexes had an opposite variation of chemical shift with respect to the same signal in the free ligands: an upfield shift for 1a (CIS 39.3 and 30.7 ppm) and a downfield shift for 2a (CIS −34.0 and −20.2 ppm) ( Table 1). (2)] (2a) [17,38]. It is reasonable to assume that the two species observed in solution for 2a were the cis and trans isomers differing for the relative position of the Pd-CH 3 fragment with respect to the two halves of the ligand.…”

Synthesis, Spectral and Solid State Characterization of a New Bioactive Hydrazine Bridged Cyclic Diphosphonium Compound

“…While searching for new ligands we have focused our attention on those that combine both hard and soft donor atoms [6][7][8][9][10][11], in particular the heterofunctionalised phosphines, where the phosphorus is the soft donor, and the hard donor is either an oxygen or nitrogen atom. Complexes of Pt(II), Pd(II), and…”