Controlling the oxidation state of arsenic in cyclic arsenic cations

Abstract

Reduction of AsCl3 with SnCl2, followed by treatment of the "AsCl" with a 1,4-diimine results in electron transfer and formation of an arsenic(III) salt, while treatment of this arsenic(I) reagent or AsI3 with an alpha,alpha'-diiminopyridine ligand forms an arsenic(I) salt.

The Role of 2,6‐Diaminopyridine Ligands in the Isolation of an Unprecedented, Low‐Valent Tin Complex

“…The CN double bonds in 3 are equal in length at 1.274(3) Å and are in good agreement with related main‐group complexes and also remain virtually unchanged compared with the uncomplexed ligand 54. 58, 59, 63…”

“…In complex 1 , the N1C1 and N2C2 double‐bond lengths are 1.308(3) and 1.321(3) Å and are in the typical range for imino bond lengths of related complexes 54. 58, 59, 63 The observation of two distinctly different separations between the central low‐oxidation‐state main‐group center and the nitrogen donors of the imino groups, as seen in 1 (Sn1N1=2.397(2) Å, Sn1N2=2.315(2) Å, Sn1N3=2.122(2) Å), is also observed in several isoelectronic DIMPY‐based pnicogen(I) compounds [DIMPYPn I ] + . In [DIMPYP I ] + I 3 − , for example, the P I N(Dipp)C separations are 1.877(7) and 1.975(7) Å.…”

“…An even more pronounced difference is found in the solid‐state structure of the B 12 Cl 12 2− salt, in which the dative interactions differ by up to 0.55 Å 55. Similarly, a slightly unsymmetrical bonding situation between the As I center and the imino nitrogen atoms is present in [MeDIMPYAs I ] 2 + As 2 I 8 2− 58. Interestingly, the CN double‐bond lengths of the imino groups in the pnicogen(I) compounds are very similar to those in compound 1 , with values of around 1.30 and 1.33 Å, and similarly short ipso ‐CCHN(Ar) lengths of between 1.39 and 1.42 Å, which connect the side arms to the central pyridine ring.…”

“…65 In addition, the Sn1N3(pyr) distance is shorter compared to the Sn1N1 and Sn1N2 between the central tin atom and the imino groups (Table 1). Related complexes with the same bonding motif as compound 1 , such as the cationic [DIMPYAs] + and [DIMPYTe] 2+ complexes, exhibit identical trends in the structural motifs with short N(pyr)E and longer (CN)E bonds 58. 59 As shown earlier, diiminopyridine ligands, which lack the opportunity to undergo enamine formation like DIMPY in PhDIMPY, cleanly react with pnicogen(I) centers (Pn I ) to give the respective cationic complexes DIMPY(Pn I ) + , which are isoelectronic to 1 and show similar bonding trends.…”

“…Of these complexes, DIMPYSn ( 1 ) is of special interest because it features a complex in which the main‐group element center is in formal oxidation state zero, in contrast to Sn II complexes 2 to 4 . Neutral DIMPYSn complex 1 is isoelectronic to the above‐mentioned cationic Group 1558 (+I) and dicationic Group 1659 (+II) derivatives (Scheme ) and to the aryl‐based Sb I and Bi I compounds 64. In analogy, complex 1 would be the first example of a neutral, mononuclear complex of tin in a formal oxidation state of zero stabilized by one donor molecule.…”