Affiliation:
1. Department of Chemistry Saint Mary's University Halifax Nova Scotia B3H 3C3 Canada
2. Department of Chemistry and Biochemistry and The Canadian Centre for Advanced Fluorine Technologies University of Lethbridge Lethbridge Alberta T1K 3M4 Canada
Abstract
AbstractThis paper presents definitive structural evidence for N,P(III)‐monophosphaamidines in P=C and N=C isomeric forms from a combination of new syntheses, single‐crystal X‐ray diffraction (SC‐XRD), solid‐state NMR and FTIR. Evidence is also provided for C‐amino‐(σ2,λ3)‐phosphaalkene and C‐(σ3,λ3)‐phosphinoimine tautomerism in solution using multi‐nuclear NMR methods. Synthesis and SC‐XRD structure determination of a trisubstituted N,N’,P(III)‐monophosphaguanidine is presented, the first structure of a phospha(III)guanidine with two ionizable H atoms. The structural evidence is convincing for an N=C geometry, resulting in both N−H and P−H in the molecule. A detailed computational investigation using DFT methods is presented, with the goal of understanding the tautomeric structure preferences both at the fundamental level (parent molecules with all substituents on the heteroatoms being hydrogen) and using the full structures containing the very bulky 2,6‐diisopropylphenyl (Dipp) substituents employed in this study. Arguments are espoused for treating phospha(III)amidines and ‐guanidines as new types of functional groups, similar to but distinct from the familiar organic analogues. Limited reactivity studies and a voltammetry study of one phospha(III)amidine are included with the supporting information.