Stimuli‐Responsive Frustrated Lewis‐Pair‐Type Reactivity of a Tungsten Iminoazaphosphiridine Complex

Abstract

Reactions of 3-imino-azaphosphiridine complexes 1 a,b with carbodiimides 2 a,b, isocyanates 3 a,b, and carbon dioxide are described. Whereas exchange of the carbodiimide unit occurs in the first case, an overall ring expansion takes place with phenyl isocyanate (3 a) and carbon dioxide to yield complexes 4 and 5 bearing novel 1,3,5-oxazaphospholane ligands; the isopropyl derivative 3 b did not react under these conditions. DFT calculations provide insight into the pathway of the reaction with carbon dioxide with model complex 1 c, revealing effects of initial non-covalent interactions with the substrate onto the ring bonding, thus triggering an initially masked frustrated Lewis-pair-type behavior.

Between Oxirane and Phosphirane: The Spring‐loaded Oxaphosphirane Ring

“…[41] First of all, initial van der Waals complexes are formed in both cases, either through hydrogen bonds or O•••P pnictogen bonds [42] (1 a1•MeOH P and 1 a5•MeOH P ), the latter profiting from a Lewis pair interaction of the lone pair at the O with the P atom σ-hole [43] (Figure 4) with bonding distance of 2.784 and 2.906 Å, respectively. As previously noticed for the case of 3imino-azaphosphiridine complexes, [44] this preliminary pnictogen bond formation entails a small yet significant enhancement of ring strain, as deduced from the increase of G(r)/1(r) at RCP (vide supra) for both 1 a1•MeOH P (1.1815 au) and 1 a5•MeOH P (1.2068 au) compared to the respective non-interacting species (1.1574 and 1.1423 au, respectively).…”

Terminal Phosphinidene Complex Adducts with Neutral and Anionic O-Donors and Halides and the Search for a Differentiating Bonding Descriptor

“…In contrast, reactions of I with carbodiimides led to side-on adducts to P, namely, 3-iminoazaphosphiridine complexes 8 rather than typical threemembered heterocyclesdisplaying a remarkable high exchange ability through isomeric end-on carbodiimide adducts. 9 Bonding analysis of neutral complexes having end-on coordination of carbon monoxide (CO) to the P center of I also showed a striking parallelism to transition-metal coordination chemistry, 5,10 which was also reported for other nonmetal maingroup element tetrel CAAC derivatives 11 as well as silylene (H 2 Si). 12 Adducts II have been isolated as stable products with phosphane, 13 N-heterocyclic carbenes (NHCs), 14 and isocyanide 15 ligands, whereas these types of species were reported as proposed intermediates when other different ligands such as water and other group 13−16 donor atoms such as Do with polar Do−H bonds, 16 imines, 6b,c dimethylcyanamide, 17 CO, 10,15 ketones, 18 and thiourea 19 were used.…”

Quantum Chemical Calculations on CHOP Derivatives—Spanning the Chemical Space of Phosphinidenes, Phosphaketenes, Oxaphosphirenes, and COP− Isomers

“…As double bonds normally entail enlarged bond angles, their incorporation into small cyclic systems should be expected to result in an increase in the RSE, as occurs, for instance, in moving from cyclopropane to cyclopropene (RSE = 29.0 and 54.5 kcal/mol, respectively [52]). In the case of the parent oxaphosphirene ring system 1a , the RSE was computed by evaluating the energetics of appropriate homodesmotic reactions (Scheme 5), similar to those used for other three- [46,48,51,53,54,55,56,57] or four-membered [47] saturated phosphorus heterocycles. In such reactions, for the cleavage of every endocyclic X–Y (or X=Y) bond, a H n X–YH m (or H n X=YH m ) reagent is used, the valences of X and Y being completed with H atoms.…”