Sterically hindered ortho-substituted phosphatriptycenes as configurationally stable P-chirogenic triarylphosphines

[4 + 1]- and [4 + 2]-cycloadditions of a thiazole-2-thione-based 1,4-diphosphinine - broadening the scope

A broad study on [4 + 1]- and [4 + 2]-cycloaddition reactions of a thiazole-2-thione-based 1,4-diphosphinine (1) is reported, with a special focus on reversible reactions. Reactions of 1 with group 13 carbenoids DippNacNacM (M = Al and Ga) afford [4 + 1] adducts that can be classified as Al and Ga phosphides or as 7-metalla-1,4-norbornadienes. Reactions of 1 with alkynes and alkenes result in [4 + 2]-cycloaddition, affording 1,4-diphosphabarrelenes. The effect of different dienophiles on the formation of 1,4-diphosphabarrelenes and their thermal [4 + 2]-cycloreversion reactions is studied from an experimental as well as theoretical point of view, opening the door for protection/deprotection strategies in this chemistry.

Regulating iminophosphorane PN bond reactivity through geometric constraints with cage-shaped triarylphosphines

Structure-reactivity investigations and quantum-chemical parametrization of steric and electronic properties of geometrically constrained iminophosphoranes enabled the design of new frustrated Lewis pairs and revealed unusual properties at the phosphonium center embedded in the cage-shaped triptycene tricyclic scaffold.

Geometrically Deformed and Conformationally Rigid Phosphorus Trisamides Featuring an Unsymmetrical Backbone

Nonclassical P(III) centers have attracted much attention in recent years. Incorporating a P(III) center in a rigid bicyclic platform offers a particularly attractive way to invoke significant geometric distortion of the phosphorus atom that may in turn induce unusual reactivity. Although still relatively scarcely explored, phosphorus centers enforced in a non-C3 symmetry have gained significant traction lately. However, the current scaffolds are based on a relatively limited set of design principles and ligand platforms associated therewith. This work is focussed on the synthesis as well as versatile oxidation, addition and coordination chemistry of a geometrically distorted P(III) species featuring a synthetically modular, nonsymmetric trisamine platform derived from 2-(methylamino)-N-(2-(methylamino)phenyl)benzenesulfonamide.

The heterometallic one-dimensional solvated coordination polymer [NiPt2Cl6(TRIP-Py)4]n

The ditopic ligand 10-[4-(pyridin-4-yl)phenyl]-9-phospha-10-silatriptycene (TRIP-Py, C29H20NPSi) binds as a pyridine donor to NiII and as a phosphatriptycene donor towards PtII. The selectivity relies entirely on the Pearson character of the donor sites and the matching hardness of the respective metal cations. The product is the one-dimensional coordination polymer catena-poly[[[dichloridonickel(II)]-bis{μ-10-[4-(pyridin-4-yl)phenyl]-9-phospha-10-silatriptycene}-bis[dichloridoplatinum(II)]-bis{μ-10-[4-(pyridin-4-yl)phenyl]-9-phospha-10-silatriptycene}] dichloromethane pentasolvate ethanol icosasolvate], {[NiPt2Cl6(TRIP-Py)4]·5CH2Cl2·20EtOH}n (1), which retains large pores due to the inherent rigidity of the ligand. This is enabled by the caged triptycene scaffold which fixes the direction of the phosphorus donor with respect to the remaining molecule and especially the pyridyl moiety. In its crystal structure, which was determined from synchrotron data, the pores of the polymer are filled with dichloromethane and ethanol molecules. Finding a suitable model for the pore content is complicated as it is too disordered to give a reasonable atomic model but too ordered to be described by an electron gas solvent mask. This article presents an in-depth description of this polymer, as well as a discussion on the use of the bypass algorithm for solvent masks.

A Rigid Linker for Site-Selective Coordination of Transition Metal Cations: Combining an Acetylacetone with a Caged Phosphine

The combination of a soft phosphorus and a hard oxygen donor in the new ligand HacacTRIP leads to excellent site selectivity for the coordination of two different metal cations of matching Pearson character. The deprotonation step required for coordinating the acetylacetone oxygen donor further increases the selectivity. In contrast to most phosphines, the use of the caged phosphatriptycene motif enables a rigid and directional orientation of the phosphorus binding site which is required to form stable coordination network structures. In addition to the synthesis of HacacTRIP, we present its selective coordination. The deprotonated acetylacetone was selectively bound to Cu^II and Fe^III. The solid state structure of the former displays a rare axial coordination of chloroform molecules. The phosphorus donor was selectively coordinated to the monovalent coinage metal cations Cu^I, Ag^I, and Au^I. The Cu^I and Ag^I complexes represent the first examples in which a phosphatriptycene is bound to these metal cations. Heterometallic coordination compounds were characterized with combinations of these two groups. They comprise an oligonuclear Cu^I/Cu^II mixed-valence compound in which iodide binds to both Cu^I and Cu^II cations and a complex in which acacTRIP^- bridges Cu^II and Au^I. In addition to these discrete aggregates, the ligand has been used to link Fe^III and Ag^I into a 2D coordination polymer with unprecedented trigonal planar coordination of three bulky phosphatriptycenes to a cation and resulting honeycomb topology. Its almost regular hexagons underline the desired rigidity of the ditopic acacTRIP^- ligand.

9-Phosphatriptycene Derivatives: From Their Weak Basicity to Their Application in Frustrated Lewis Pair Chemistry

The accurate prediction of the basicity of tertiary phosphines in acetonitrile and water is reported by the linear correlation between computed ΔpK_a's obtained by density functional theory (DFT) and experimental values extracted from the literature. This method is applied to the prediction of pK_a values of 9-phosphatriptycene derivatives and showed that they are weaker Brønsted bases than their triphenylphosphine analogues. This lower reactivity is attributed to their high pyramidalization that increases their lone pair 3s character, stabilizing its energy level. Their potential application in frustrated Lewis pair chemistry is then considered by investigating the hydrogenation of 1,1-diphenylethylene by the tris(pentafluorophenyl)borane/1-chloro-9-phosphatriptycene frustrated Lewis pair.

Phosphorus or Nitrogen - The first Phosphatriptycene in Coordination Polymer Chemistry

Phosphasilatriptycene, a phenylene spacer and a pyridyl moiety represent the building blocks of TRIP-Py, the first heteroditopic ligand featuring a phoshatriptycene scaffold. The P and N donor sites located at...