Periodicity in Structure, Bonding, and Reactivity for P-Block Complexes of a Geometry-Constraining Triamide Ligand

Abstract

The use of pincer ligands to access non-VSEPR geometries at main-groupc enters is an emerging strategy for elicitingn ew stoichiometric and catalytic reactivity.A sp art of this effort, severald ifferent tridentatet rianionic substituents have to dateb een employed at ar ange of different centrale lements, providing ap atchworkd ataset that precludes rigorouss tructure-function correlation.A na nalysis of periodic trendsi ns tructure (solid, solution, and computation), bonding, and reactivity based on systematic variation of the central element( P, As, Sb, or Bi)w ith retentiono fa single tridentate triamides ubstituent is reported herein. In this homologous series, the centrale lement can adopt either ab ent or planar geometry.T he tendency to adopt planarg eometries increases descending the group with the phosphorus triamide( 1)a nd its arsenic congener (2)e xhibiting bent conformations,a nd the antimony (3)a nd bismuth (4)a naloguese xhibiting ap redominantly planar structure in solution.T his trend has been rationalized using an energy decomposition analysis. Ar arep hase-dependent dynamic covalentd imerizationw as observed for 3 and the associated thermodynamic parameters were establishedq uantitatively. Planarg eometries were found to engender lower LUMO energiesa nd smaller band gaps than bent ones, resulting in different reactivity patterns.T hese results provide ab enchmark dataset to guidef urtherr esearchi nt his rapidlye merging area.

Squeezing Bi: PNP and P2N3 Pincer Complexes of Bismuth(III

“…Compound 1 exhibits good solubility in a range of organic solvents and has therefore been fully characterized in solution and the solid state. The 31 P NMR spectrum of 1 shows a sharp singlet at 23.3 ppm and the 1 H and 13 C NMR spectra suggest a C2 ligand symmetry with equivalent phosphinimine environments. Single crystals of 1 were obtained from a saturated DCM solution at -30 o C and confirmed the meridional arrangement inferred from solution NMR data (Figure 2a, Table 1).…”

“…We are interested in rational frontier orbital engineering at heavy main group centres through such geometric perturbations. [11][12][13][14] Considering the L2X pincer ligand coordination chemistry of bismuth (Figure 1), we noted that this area is dominated by the use of the NCN motif based on 2,5-substituted aryl groups. [15][16][17][18][19][20][21][22][23][24][25][26] Planar NCN-Bi complexes have been shown to activate challenging small molecules 19,20,27 and, more recently, found applications in hydrogen transfer catalysis.…”

“…32 In this context, we recently reported complex NNN-Bi, where a trianionic substituent undergoes intramolecular oxidation to become monoanionic, concomitant with reduction of the chelated Bi(III) centre to a formal Bi(I) oxidation state, as deduced from spectroscopic analysis and reactivity studies. 11,13 In seeking to further evolve the pincer ligand chemistry of bismuth, we have now explored the use of two new frameworks that are little-studied in p-block chemistry and unknown in bismuth chemistry.…”