Synthesis and properties of air-stable 1,3-diphosphacyclobutane-2,4-diyls and the related compounds

Poly(Biradicals): Oligomers of 1,3‐Diphosphacyclobutane‐2,4‐diyl Units

“…Nonetheless, it is possible to discuss gross conformational features of the molecule. Each four‐membered biradical unit displays a structure similar to the known 1,3‐diphosphacyclobutane‐2,4‐diyls5a, c, d with a distortion in the sterically encumbered Mes* groups, as we have reported 12. Interestingly, in spite of the steric congestion, two bulky biradical units are positioned on the same side of the xylyl moiety in a syn ‐type conformation; the shortest P⋅⋅⋅P separation is 6.5 Å.…”

Study of the Air‐Tolerant 1,3‐Diphosphacyclobutane‐2,4‐diyl through the Direct Arylation

“…The smaller pyramidalization of the t BuP phosphorus atom and shorter P( t Bu)–C1/C2 bonds would correlate with the electron‐donating character of the t ‐butyl group. The 31 P NMR spectroscopic data show the larger‐field chemical shift of the t BuP group,,,, which might be due to the canonical formula. The molecular structure of 8 indicated that the isopropylamino group increases the electron‐donating property of the P‐heterocyclic chromophore .…”

“…Positioning the sterically encumbered Mes* substituents is quite effective to stabilize the cyclic biradical (biradicaloid) skeleton, and handling of 1 in air at ambient temperatures is possible. The synthetic procedures of 1 including nucleophilic alkylation, acylation, and sulfanylation of the P‐heterocyclic anionic intermediates ( CBA ) was advantageous to afford a number of 1,3‐diphosphacyclobutane‐2,4‐diyls . Furthermore, the alkylation process was applicable to catenate the open‐shell singlet P‐heterocyclic units to construct the tetraradical and hexaradical derivatives showing the through‐space static interaction .…”

Intensive NMR study of 1‐t‐butyl‐3‐methyl‐2,4‐bis(2,4,6‐tri‐t‐butylphenyl)‐1,3‐diphosphacyclobutane‐2,4‐diyl

“…Chemical shifts for different phosphorus centers have been discussed in terms of configuration of the phosphorus centers [8,9]. Unexpectedly, when the spectrum was recorded in a protoncoupling mode (zg 30), the lower part of an AB set (centered at 54.8 ppm, assigned P 1 ) with a coupling constant of 2 J PP = 358.2 Hz became a doublet of dectet with coupling constant of 14 Hz, whereas the upper doublet (centered at −12.8 ppm, assigned as P 2 ) apparently remained unchanged in the proton- decoupled mode, suggesting that P 2 does not couple strongly with any protons.…”