Complexation Studies with a Calix[4]arene-Derived Phosphinite − Divergent Arrays of Cavities Linked by MCl2 Fragments (M = Pd, Pt)

Abstract

A cone‐shaped calix[4]arene‐derived monophosphinite, 25,27‐di(ethoxycarbonylmethoxy)‐26‐hydroxy‐28‐(diphenylphosphinooxy)calix[4]arene (L1), has been prepared in two steps from calix[4]arene. Treatment of L1 with [AuCl(tetrahydrothiophene)] in tetrahydrofuran gave the phosphinite complex [AuClL1] (1). Reaction of [PdCl2(PhCN)2] with two equivalents of L1 gave selectively trans‐[PdCl2L12] (2). Complex 2 · 2 CH2Cl2 crystallizes in the triclinic space group P1¯. The molecule is centrosymmetric, leading to a divergent array of the two calixarene moieties. The palladium atom resides outside both cones. As a result of steric interactions, the meta and para carbon atoms of the PPh2‐bearing aryl ring are significantly pushed to the interior of the cavity. The related platinum complex trans‐[PtCl2L122] (3), was obtained similarly from [PtCl2(PhCN)2] and presents in the solid state a structure which is isomorphous to that of 2. The diphosphinite 25,27‐di(ethoxycarbonylmethoxy)‐26,28‐bis(diphenylphosphinoxy)calix[4]arene (cone) (L2) has also been prepared and reacts with [PtCl2(PhCN)2] to yield oligomeric material.

A Silsesquioxane-Based Diphosphinite Ligand: Synthesis, DFT Study, and Coordination Chemistry

“…These bond lengths fall within the expected range, compared to those of other [PdCl 2 (P) 2 ] complexes described in the literature. − The trans -[PdCl 2 (P) 2 ] complex (P is a calix[4]arene-derived monophosphinite) of Faidherbe et al showed the largest deviation, with a Pd−P bond length of 2.3251(6) Å . Furthermore, the palladium−chloride bond distances Pd 1 −Cl 1 (2.3589(10) Å) and Pd 1 −Cl 2 (2.3591(10) Å) are in their normal ranges. − The silyl ether bonds Si 5 −O 2 and Si 6 −O 1 are long at 1.672(3) and 1.660(2) Å, compared to the average Si−O bond lengths of the silsesquioxane framework (average 1.62 Å), indicative of a lower electron density in the former bonds. The Si 8 −O 3 bond length is 1.636(3) Å, similar to those for other SiMePh 2 -containing structures reported by Duchateau and slightly longer compared to values found with SiMe 3 as the substituent .…”

“…There is a significant tetrahedral distortion in the coordination plane around the palladium atom, illustrated by the calculated dihedral angle between the P 1 −Pd−P 2 plane and the Cl 1 −Pd−Cl 2 plane of 18°. The P−O bond lengths of 1.584(2) Å (P 1 −O 2 ) and 1.601(2) Å (P 2 −O 1 ) are found to be smaller than the values normally reported in the literature for phosphinites coordinated to palladium. − , This is another indication that the silsesquioxane framework indeed possesses electron-withdrawing character.…”

“…The P-O bond lengths of 1.584(2) Å (P 1 -O 2 ) and 1.601(2) Å (P 2 -O 1 ) are found to be smaller than the values normally reported in the literature for phosphinites coordinated to palladium. [23][24][25][26]29 This is another indication that the silsesquioxane framework indeed possesses electron-withdrawing character. Preparation of Dichloroplatinum(II) Complex 6.…”

“…26 Furthermore, the palladium-chloride bond distances Pd 1 -Cl 1 (2.3589(10) Å) and Pd 1 -Cl 2 (2.3591(10) Å) are in their normal ranges. [23][24][25][26] The silyl ether bonds Si 5 -O 2 and Si 6 -O 1 are long at 1.672(3) and 1.660(2) Å, compared to the average Si-O bond lengths of the silsesquioxane framework (average 1.62 Å), indicative of a lower electron density in the former bonds. The Si 8 -O 3 bond length is 1.636(3) Å, similar to those for other SiMePh 2 -containing structures reported by Duchateau 27 and slightly longer compared to values found with SiMe 3 as the substituent.…”

Synthesis of Pd(II) and Pt(II) complexes possessing bicyclo[3.2.0]heptanyl phosphinite ligands: Identification of a novel Pd(II) precatalyst for 1,6-diene cycloisomerisation

“…4). Both the Pd-P and Pd-Cl distances (2.3450(3) and 2.3132(3) Å , respectively) are longer than in the only one previously studied trans-bis-phosphinite-dichloropalladium(II) complex, PdCl 2 (PPh 2 OR) 2 , where R is a bulky calixarene moiety (Pd-P 2.325 (1), Pd-Cl 2.301(1) Å ) [19]. The differences in Pd-P distances can be attributed to weaker electron withdrawal by t-Bu compared to Ph groups and hence higher basicity of the P atom in 15, while the elongation of Pd-Cl is probably caused by intramolecular hydrogen bonds O-HÁ Á ÁCl (Fig.…”