Diverse Bonding Activations in the Reactivity of a Pentaphenylborole toward Sodium Phosphaethynolate: Heterocycle Synthesis and Mechanistic Studies.
The reaction of the pentaphenylborole [(PhC)4BPh] (1) with sodium phosphaethynolate·1,4-dioxane (NaOCP(1,4-dioxane)1.7) afforded the novel sodium salt of phosphaboraheterocycle 2. It comprises anionic fused tetracyclic P/B-heterocycles that arise from multiple bond activation between the borole backbone and [OCP]-anion. Density functional theory calculations indicate that the [OCP]-anion prefers the form of phosphaethynolate-O-C≡P over phosphaketenide O═C═P-to interact with two molecules of 1, along with various B-C, C-P, and C-C bond activations to form 2. The calculations were verified by experimental studies: (i) the reaction of 1 with NaOCP(1,4-dioxane)1.7and a Lewis base such as the N-heterocyclic carbene IAr[:C{N(Ar)CH}2] (Ar = 2,6-iPr2C6H3) and amidinato amidosilylene [{PhC(NtBu)2}(Me2N)Si:] afforded the Lewis base-pentaphenylborole adducts [(PhC)4B(Ph)(LB)] (LB = IAr(3), :Si(NMe2){(NtBu)2CPh} (4)), respectively; (ii) the reaction of 1 with the carbodiimide ArN═C═NAr afforded the seven-membered B/N heterocycle [B(Ph) (CPh)4C(═NAr)N(Ar)] (5). Compounds 2-5 were fully characterized by NMR spectroscopy and X-ray crystallography.
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University , 637371 Singapore.
Yan
Y
Li
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University , 637371 Singapore.
Rahul Kumar
RK
Siwatch
Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata , Mohanpur 741 246, India.
Totan
T
Mondal
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University , 637371 Singapore.
Yongxin
Y
Li
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University , 637371 Singapore.
Rakesh
R
Ganguly
Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata , Mohanpur 741 246, India.
Debasis
D
Koley
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University , 637371 Singapore.
Cheuk-Wai
http://orcid.org/0000-0003-4816-9801
CW
So