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. 2024 Jul 29;4(10):3777-3787.
doi: 10.1021/jacsau.4c00347. eCollection 2024 Oct 28.

Strain-Releasing Ring-Opening Diphosphinations for the Synthesis of Diphosphine Ligands with Cyclic Backbones

Chandu G Krishnan  1   2 , Hideaki Takano  1   2 , Hitomi Katsuyama  1   2 , Wataru Kanna  3 , Hiroki Hayashi  1   2 , Tsuyoshi Mita  1   2
Affiliations

Strain-Releasing Ring-Opening Diphosphinations for the Synthesis of Diphosphine Ligands with Cyclic Backbones

Chandu G Krishnan et al. JACS Au. .

Abstract

Diphosphine ligands based on cyclobutane, bicyclo[3.1.1]heptane, and bicyclo[4.1.1]octane were synthesized from the corresponding highly strained, small, cyclic organic molecules, i.e., bicyclo[1.1.0]butane, [3.1.1]propellane, and [4.1.1]propellane, employing a ring-opening diphosphination. Under photocatalytic conditions, the three-component reaction of a diarylphosphine oxide, one of the aforementioned strained molecules, and a diarylchlorophosphine results in the smooth formation of the corresponding diphosphines in high yield. The obtained diphosphines can be expected to find applications in functional molecules due to their unique structural characteristics, which likely impart specific properties on their associated metal complexes and coordination polymers (e.g., a zigzag-type structure). The feasibility of the initial radical addition can be estimated using density-functional-theory calculations using the artificial force induced reaction (AFIR) method. This study focuses on the importance of integrating experimental and computational methods for the design and synthesis of new diphosphination reactions that involve strained, small, cyclic organic molecules.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Scheme 1
Scheme 1. Importance of Bidentate Phosphine Ligands
Scheme 2
Scheme 2. 3CR for the Synthesis of Diphosphine Ligands
Figure 1
Figure 1
3CR of cyclopropane with 1 and 2.
Figure 2
Figure 2
3CR of bicyclo[1.1.0]butane.
Figure 3
Figure 3
3CR of sulfonylated bicyclo[1.1.0]butane. a0.7 mmol-scale synthesis.
Figure 4
Figure 4
Removal of the sulfonyl group under Mg-mediated conditions.
Figure 5
Figure 5
Conversion of 4bb-cis to cis-coordinate Ni-complex NiCl2(8bb-cis). Bottom right: crystal structure of NiCl2(8bb-cis) with thermal ellipsoids at 50% probability; all hydrogen atoms as well as one molecule of CH2Cl2 have been omitted for clarity.
Figure 6
Figure 6
Plausible reaction mechanism based on DFT calculations for the 3CR with bicyclo[1.1.0]butane. The reaction diagrams were calculated at the UωB97X-D/Def2-SVP/SMD(DCM) level.
Figure 7
Figure 7
3CR of [3.1.1]propellane. aWhite LED irradiation for 24 h without a photocatalyst.
Figure 8
Figure 8
Synthesis of diphosphine ligands and metal complexes. Bottom right: crystal structures of 12 and 12′ with thermal ellipsoids at 30% probability; fluorine atoms on the hfa ligands and all hydrogen atoms are omitted for clarity.
Figure 9
Figure 9
Plausible reaction mechanism based on DFT calculations for the 3CR with [3.1.1]propellane. The reaction diagrams were calculated at the UωB97X-D/Def2-SVP/SMD(DCM) level.
Figure 10
Figure 10
3CR of [4.1.1]propellane.
Figure 11
Figure 11
Conversion to free diphosphine ligands.
Figure 12
Figure 12
Plausible reaction mechanism based on DFT calculations for the 3CR with [4.1.1]propellane. The reaction diagrams were calculated at the UωB97X-D/Def2-SVP/SMD(DCM) level.
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