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. 2016, 22, 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 2020, 40, 25-51. DOI: 10.1080/02603594.2019.1701447

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

Switching from NCN to OCO pincers with sp3-hybridized benzylic arms (to prevent the formation of aromatic P-heterocycles) was expected to strengthen the 3-center, 4-electron O–P–O bond of the targeted 10–P–3 species, BUT unexpected and interesting reactivity was observed. Subjecting an O-Mes substituted pincer to the lithiation/phosphination/reduction protocol afforded to an (RP)3 species (R = OCO pincer), a cyclotriphosphane, while use of a modified Martin Ligand led to cyclization and dealkylation. Currently (Summer 2021), new OCO pincers not likely to form these "byproducts" are being developed.

These results were disclosed here:

Chinen, B.L.; Hyvl, J.; Brayton, D.F.; Riek, M.M.; Yoshida, W.Y.; Chapp, T.W.; Rheingold, A.L.; Cain, M.F. RSC Advances, 2021, 11, 28602-28613.

DOI: 10.1039/d1ra05926b

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 2016, 35, 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

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 2016, 35, 2224-2231. DOI: 10.1021/acs.organomet.6b00250

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