Executive Summary : | Stabilization of carbene-supported, heterodiatomic heavier main group species and exploring their intriguing reactivities and fascinating bonding scenarios have become challenging targets for synthetic main group chemists since the last decade. Phosphinidenes are the reactive group-15 analog of carbenes. Recently, the PI’s group has reported an improved and easily accessible synthetic route for stabilizing metal-phosphinidenides in excellent yields, and herein, the PI proposes that the electron-rich, carbene-supported metal-phosphinidenides can successfully stabilize the electron-deficient group-13 and the electron-rich group-15 heavier elements at their lower valency due to the comparable electronegativities. Group-13 compounds, especially those of B and Al are well-known electrophiles. The utilization of various carbenes by different research groups to stabilize exotic B and Al compounds have been reported. However, the synthesis of mixed main group 13/15 compounds, L=E-E′=L (L = carbene, E = P, E′ = B, Al, Sb) have always remained challenging. In this context, the synthesis of iminoboranes (L-N=B-L) is noteworthy. However, their P-analogues remain elusive to date. As a result of the large electronegativity difference between N and B, the iminoborane chemistry is majorly dominated by the polarity of the BN triple bonds. In contrast, B and P having similar electronegativities, the boryl/aluminyl-phosphinidenes, L=P-B/Al=L are expected to display significantly different reactivity. The major aim of this project is to stabilize the unprecedented low coordinate B and Al compounds by using carbene-supported phosphinidenes to afford boryl/aluminyl-phosphinidenes. Similarly, due to comparable electronegativity of heavier group-15 elements, e.g., Sb, the synthetic route for the corresponding stibanyl-phosphinidenes L=E-E′=L (L = carbene, E = P, E′ = Sb) will also be targeted. Challenging synthetic strategies have been proposed herein for stabilization of low-valent, exotic P-B/P-Al/P-Sb compounds, aiming their solid-state isolation, characterization, bonding analysis (DFT, EDA-NOCV), and studies of their redox properties to understand the feasibility of concomitant electron transfer processes in solution to stabilize the corresponding radicals/ radical anions or radical cations. As a part of the major applications of the proposed molecules under the present proposal, the PI’s group will be studying their intriguing photo-physical properties as this has been precedented by a few exotic carbene-stabilized group-13 compounds. Most importantly, the thermally activated delayed fluorescence (TADF) for the proposed molecules will be studied to focus on the interesting commercial applications of these species in organic light-emitting diodes (OLEDs). Based on the fact that carbenes can potentially activate small molecules, the next objective will be to utilize the proposed molecules for C-O bond activation reactions and homogeneous catalysis. |