Paddlewheel 1,2,4-diazaphospholide dibismuthanes with very short bismuth–bismuth single bonds

Abstract

One-electron oxidation of the 1,2,4-diazaphospholide anion [3,5-R2dp](-) by BiCl3 generated several remarkable paddlewheel dibismuthanes [L2(Bi-Bi)L2] (L = η(1),η(1)-3,5-R2dp, R = tBu, iPr, or Ph) with very short Bi-Bi single bond lengths (2.7964(4)-2.8873(3) Å).

Paddlewheel 1,2,4-diazaphospholide distibines with the shortest antimony–antimony single bonds

“…[7][8][9][10] As mentioned, the p-block paddlewheel dibismuthane {(η 1 ,η 1 -3,5-R 2 dp) 2 (Bi-Bi)(η 1 ,η 1 -3,5-R 2 dp) 2 } (B) 4 was prepared by one-electron reduction of BiCl 3 with the non-innocent 1,2,4diazaphospholide anions. 4 This effect makes the Bi-Bi σ bonding interactions strong enough to yield complexes that are sufficiently stable. 4 The Bi-Bi bond lengths are very short, ranging from 2.7964(4) to 2.8873(3) Å.…”

“…11,12 This family of complexes was easily isolated by recrystallization. 4 The ability to successfully prepare B was apparently caused by the unique electronic nature of the non-innocent ligands that may favor the p-block paddlewheel complexes. The bond length of the one is even shorter than those of the BivBi double bond distances found in dibismuthenes (about 2.82 Å).…”

“…Therefore, the one-electron oxidation of 1 (or 2 or 3) produced the neutral radical [3,5-R 2 dp] • (R = tBu, iPr, or Cy) that spontaneously abstracted a hydrogen from a THF molecule to give the corresponding free ligand H[3,5-R 2 dp], 11,25 similar to the mechanism with the formation of the paddlewheel dibismuthanes in THF. 4 Compound 10 was isolated as colorless crystals in ca. The resultant mixture was monitored by the 1 H and 31 P{ 1 H} NMR spectroscopy.…”

“…4). 5, we provide the simplified fragment orbital interaction diagrams for the key molecular orbitals of [Sb 2 (3,5-tBu 2 dp) 4 ], based on the results of the M11 method. 27d The orbital in which the remaining lone pair of the electrons is located has a basically s orbital contribution.…”

“…interactions in a 1 irreducible orbitals of [Sb 2 (3,5-R 2 dp) 4 ] obtained by the M11 method are somewhat different from those a 1 irreducible orbitals in [Bi 2 (3,5-tBu 2 dp) 4 ]: a 1 irreducible frontier molecular orbitals, HOMO−1, HOMO−6 and HOMO−13 of [Sb 2 (3,5-tBu 2 dp) 4 ] are composed of not only a 1 irreducible fragment orbitals HOF 1 O and HOF 2 O−15 (basically σ-type fragment orbitals) but also a 1 symmetry fragment orbitals HOF 2 O−11 (basically π-type fragment orbitals). In HOMO−1/HOMO−6/HOMO−13, the contributions from HOF 1 O, HOF 2 O−11 and HOF 2 O−15 are (25%)/(∼0%)/(58%), (21%)/(53%)/(12%) and (34%)/(34%)/(18%), respectively.…”