Cyclo-Pnicta-triazanes: Biradicaloids or Zwitterions?

Abstract

Bulky triazenides were utilized in the reaction with pnictogen(III) chlorides (ECl3, E = P, As, Sb, and Bi) yielding triaza-pnicta-butene analogues of the type R-N═N-N(R)-ECl2 (R = Ter = 2,6-bis(2,4,6-trimethylphenyl)phenyl). Subsequent reduction of these dichloro-species afforded unprecedented four-membered group 15 heterocycles [E(μ-NTer)2N] bearing one dicoordinate pnictogen and nitrogen atom. These N3E rings represent species at the borderline between singlet biradicaloids and zwitterions with diminished reactivity compared to known singlet biradicaloids. The N3P compound could be identified, while N3As and N3Sb species as well as the precursor compounds were fully characterized.

Synthesis of a Molecule with Four Different Adjacent Pnictogens

“…The in‐plane Sb−Cl2 bond with a length of 2.3596(4) Å is slightly shorter than the out‐of‐plane Sb−Cl1 bond 2.3835(3) Å, which can be attributed to a hyperconjugative effect of the nitrogen lone pair interacting with the parallel‐lying σ*(Sb−Cl1) orbital (38 kJ mol −1 ) according to a natural bond orbital analysis . Such delocalization effects are also known from molecules consisting of [SbCl 2 ] moieties and amindinate or guanidinate substituents, or examples from our group, for example, Ter 2 N 3 SbCl 2 and Ter 2 N 2 PSbCl 2 . The As−P bond length (As1−P1 2.1444(4) Å) is in good agreement with the expected value for a double bond (Mes*‐As=P‐Mes* 2.141(5), Σ r cov (As=P)=2.16 Å), while both the As−N and Sb−N bond lengths compare well to polarized single bonds (As−N 1.850(1), Sb−N 2.055(1); cf.…”

“…Depending on the pnictogen combination the reaction between A and ECl 3 can either result in the open‐chain species B or the cyclic species C . The concept could be applied for triazenides (E 1 =N) as well cleanly affording open‐chain species of the type TerN(ECl 2 )NNTer ( B ) and cyclic species D upon reduction …”

Metal‐Free Activation of Hydrogen, Carbon Dioxide, and Ammonia by the Open‐Shell Singlet Biradicaloid [P(μ‐NTer)]2

“…Earlier investigations had shown that biradicaloid 1 can be prepared on gram scale and that it is highly reactive,b ut stable in solution and in the solid state under argon atmosphere. [45] The 31 PNMR resonance of 2 was observed as an AA'XX' pattern centered at 193.9 ppm (Figure 1, left;f or sections of the 1 HNMR spectra, see the Supporting Information, Figure S1). Interestingly, 31 PNMR experiments indicated the presence of only one isomer of 2.…”

Reduction of dichloro(diaza-phospha)stibanes – isolation of a donor-stabilized distibenium dication

“…59 Therefore, it can be deduced that the symmetrically bridging NPN ligand retains its anionic nature in the bridging mode, as indicated by these phosphorus-nitrogen bond lengths, which is similar to analogous structures with μ-N,N′ bridging complexes (cf. It is interesting to note that the isovalence-electronic triazenide species, [N(µ-NTer) 2 Sb], 62 exists as a monomeric compound and does not dimerize to form the distibenium bicyclic species. The molecular structure of heterocycle 6 is reminiscent to the (NCN) 2 P 2 scaffold of [P 2 {µ-(MesN) 2 CNMes} 2 ].…”