Research

We love synthesis.  

We try to prepare hypervalent or low-coordinate phosphorus species OR transition metal complexes

supported by new multidentate phosphorus-derived ligands within a well-defined, high-energy geometry

with the goal of promoting strong bond activation that can be incorporated into a catalytic cycle.   

 

Project:  Hypervalent P

1.  Phosphinidene (R–P) Generation Within an NCN Pincer Ligand

Our first paper in which we tried to isolate a phosphinidene within an NCN pincer resulted in the discovery of an aromatic azaphosphole "bell-clapper". Dynamic scaffolds of this nature are rare, but were observed by J.C Martin (in the 1970s and 80s) during his investigations to isolate molecules featuring pentavalent carbons!  Check it out!

   

 

 

 

 

Our preliminary communication is reported here:

Hyvl, J.; Yoshida, W.Y.; Rheingold, A.L.; Hughes, R.P.; Cain, M.F.  Chem. Eur. J.  201622, 17562-17565.  DOI:  10.1002/chem.201604415

 

Related chemistry reported in a special issue in Polyhedron is reported here:

Hyvl, J.; Yoshida, W.Y.; Moore, C.E.; Rheingold, A.L.; Cain, M.F.  Polyhedron  2018, 143, 99-104.

If you cannot access these articles, email me and I will provide a PDF.

"Offshoot" and Ongoing Project:  New Pnictogen-Containing Heterocycles.  Azaphospholes and -arsoles.  

We discovered that if a P(I)/As(I) center was generated within a simpler NC chelate (rather than an NCN pincer) that a similar redistribution of electron density occurred, resulting in the synthesis of new PN and AsN heterocycles without the tethered imine donor.  These molecules are 10 pi-electron species that have demonstrated some interesting reactivity.   

 

A full article on the synthesis of static aromatics, "bell-clappers", and hypervalent Group 15 derivatives,

new benzoazaphospholes and arsoles, and detailed calculations on their aromaticity can be found here:

Kremláček, V.; Hyvl, J.; Yoshida, W.Y.; Růžička, A.; Rheingold, A.L.; Turek, J.; Hughes, R.P.; Dostál, L.; Cain, M.F.

 Organometallics  2018, 37, 2481-2490.  DOI: 10.1021/acs.organomet.8b00290

If you cannot access this article, email me and I will provide a PDF.

Functionalized (Dearomatized) Benzazaphospholes as Transmetalating Agents

Sequential treatment of benzazaphospholes with HCl followed by a nucleophile affords new 6 pi-electron species with an exocyclic P–X bond that is elongated due to hyperconjugation with the adjacent N atom (see the papers cited below for a detailed explanation to why).  This renders normally inert P–C bonds more labile, which we exploited to generate new transmetalating agents for Pd-catalyzed cross-coupling.  If the functionalized benzazaphosphole is a P–CCPh derivative, we demonstrated that the alkynyl unit could be transferred to Pd(II) in a stoichiometric fashion and ultimately, used in catalysis for a "Cu-free" Sonogashira-type reaction.  

 

Currently (1/2021), we are addressing the limitations associated with the alkynylation reaction, while simultaneously synthesizing new P–functionalized (X = CF3, etc) heterocycles.  

 

 

 

 

 

 

 

A full article on these new P-Alkynyl Functionalized Benzazaphosphole as Transmetalating Agents can be found here:

Zhou, D.Y.; Miura-Akagi, P.M.; McCarty, S.M.; Guiles, C.H.; O'Donnell, T.J.; Yoshida, W.Y.; Krause, C.E.; Rheingold, A.L.;

Hughes, R.P.; Cain, M.F. Dalton Trans. 2021, 50, 599-611.  DOI: 10.1039/D0DT01367F

 

A critical review on benzazaphospholes from MFC can be found here:

Cain, M.F. Comments on Inorganic Chemistry 202040, 25-51.  DOI:  10.1080/02603594.2019.1701447

2.  Phosphinidene (R–P) Generation Within OCO Pincer Ligands 

(Add description soon ... hypothesis, unexpected results, etc.)

1a.png
1aa.png
Screen Shot 2018-07-19 at 11.53.06 AM.pn
Screen Shot 2020-12-30 at 10.01.31 AM.pn
Screen Shot 2020-12-30 at 10.01.54 AM.pn

Project: New Well-Defined Ligand Architectures

1.  Simple Bidentate Ligands:

A.  Phosphine-Phosphaalkene Hybrids

All of these targets were disclosed in our first paper in Organometallics that went online 3/16/2016

 

Magnuson, K.W.; Oshiro, S.M.; Gurr, J.R.; Yoshida, W.Y.; Gembicky, M.; Rheingold, A.L.; Hughes, R.P.; Cain, M.F.  Organometallics  201635, 855-859.  DOI: 10.1021/acs.organomet.6b00101

 

If you cannot access the article, email me and I will provide a PDF.  

B.  Pyridine-Phosphaalkene Hybrids

1.png

Nakashige, M.L.; Loristo, J.I.P.; Wong, L.S.; Gurr, J.R.; O'Donnell, T.J.; Yoshida, W.Y.; Rheingold, A.L.; Hughes, R.P.; Cain, M.F. Organometallics 2019, 38, 3338-3348.  DOI: 10.1021/acs.organomet.9b00425

2. Tetradentate Tris(phosphaalkene)phosphine ligands: Reactivity within an electron-rich Rh/Ir Pocket                                   

Coming soon ... Pincers? :)

 

 

See the publication tab for a list of all of our publications.  

 

Our new PP3 ligand and its corresponding metal complexes were reported in the following paper:

Miura-Akagi, P.M.; Nakashige, M.L.; Maile, C.K.; Oshiro, S.M.; Gurr, J.R.; Yoshida, W.Y.; Royappa, A.T.; Krause, C.E.; Rheingold, A.L.;

Hughes, R.P.; Cain, M.F.  Organometallics  201635, 2224-2231.  DOI:  10.1021/acs.organomet.6b00250

If you cannot access the article, email me and I will provide a PDF.