Between Adamantane and Atrane: Intrabridgehead Interactions in the Cage‐Like Phosphane Related to a Novel Tris(homoadamantane) Ring System

Abstract

Herein, we report unusual four-center interactions in the novel cage-like phosphane, 1,4,7-triaza-9-phosphatricyclo[5.3.2.1(4,9) ]tridecane (CAP). This water-soluble ligand, the first example of a tris(homoadamantane) ring system, can be considered a macrocyclic homologue of the well-known PTA (1,3,5-triaza-7-phosphaadamantane). However, (31) P NMR spectroscopic anomalies of CAP follow those typical for the bi-/tricyclic atrane systems. Another atrane-like feature of CAP is the ability of one nitrogen atom to undergo out-in pyramidal inversion. The latter is associated with a substantial decrease in the intracage N-N and P-N distances. Analysis of electron density distribution [molecular electrostatic potential (MESP) and atoms-in-molecules (AIM) approaches] suggests that the P and N atoms in the pyramidally inverted CAP derivatives are involved in interactions resulting in accumulation of electron density at the center of the phosphane cage. The latter can reliably explain the stereoelectronic and NMR anomalies of the new ligand. The semi-flexible CAP cage populates the structural niche between the rigid adamantine skeleton of PTA and flexible atrane systems and can be regarded as an alternative to PTA in aqueous coordination chemistry.

Water-soluble carbonyl complexes of 99Tc(I) and Re(I) with adamantane-cage aminophosphines PTA and CAP

“…[10]. The 31 P NMR chemical shifts for the Tc and Re pentacarbonyl complexes with CAP and PTA significantly differ from those of the free ligands [3], which is consistent with the ligand coordination mode via P atom. Causes of significant differences between the chemical shifts for the Tc and Re complexes with the same ligand and for the complexes of the same metal with CAP and PTA are not fully clear; they may be associated with specific conformational and bonding features of the complexes, requiring more detailed analysis.…”

“…Coordination chemistry of the small adamantane-cage aminophosphines, 1,3,5-triaza-7phosphaadamantane (PTA) and its recently synthesized analog 1,4,7-triaza-9phosphatricyclo[5.3.2 14,9 ]tridecane (CAP), is extensively developed [1][2][3][4][5][6].These ligands combine two kinds of donor atoms, P and N, which is of interest itself from the viewpoint of hard/soft acid-base coordination preferences. In the case of P-coordination, the uncoordinated N atoms remain available for acid-base interactions in aqueous solution (protonation), making the complexes hydrophilic.…”

Crystal structure of (1S,4S)-2,5-diazoniabicyclo[2.2.1]heptane dibromide

“…Moreover, the parent ring of unsubstituted 2,5-diazabicyclo[2.2.1]heptane has not been structurally characterized. In the framework of current research on caged heterocyclic systems (Britvin & Lotnyk, ISSN 2056-9890 2015; Britvin et al, 2016;2017a,b;, we herein describe the molecular structure of 2,5diazabicyclo[2.2.1]heptane ( Fig. 1) in its dihydrobromide salt, (1S,4S)-2,5-diazoniabicyclo[2.2.1]heptane dibromide (1).…”

Ruthenium(II)-Arene Complexes of the Water-Soluble Ligand CAP as Catalysts for Homogeneous Transfer Hydrogenations in Aqueous Phase

“…As PTA, this compound is a white, air-stable solid under standard conditions, and it is moderately water soluble with S(H2O)25 °C = 20 g L −1 , about one order of magnitude lower than for PTA. Although structurally very similar to PTA, CAP has a higher cage flexibility due to the presence of two CH2 spacers between the N atoms instead of one [23,24]. The Ru(II) complex κP-[RuCl2(η 6 -p-cymene)(CAP)] (1, Figure 2) was obtained by reacting [RuCl2(η 6 -p-cymene)]2 with 2 equiv.…”