Open Chain Polyarsenides of the Lanthanides

Abstract

The reaction of [(Cp'''Co) (μ,η -As ) ] with the decamethylsamarocenes [Cp* Sm(THF) ] or [Cp* Sm], or the bis(tetramethyl-n-propyl)samarocene [(C Me (n-propyl)) Sm] resulted in the mixed d/f polyarsenides [(Cp'''Co) As Sm(η -C Me R) ] (R=Me, n-propyl). They are the first structural representatives of open chain-like polyarsenides as ligands in the coordination sphere of lanthanides. Their formation can be explained by an intramolecular As-As coupling within the cobalt polyarsenide complex after reduction by the divalent samarium complex. Density functional theory calculations give insight into the structural change of the (As ) unit in [{Cp'''Co(μ,η -As )} ] upon reduction.

Samarium Polyarsenides Derived from Nanoscale Arsenic

“…In addition, the As1−As1′ bond length is consistent with a double bond rather than a single bond, as {As=As} 2− moieties exhibit bond lengths of 2.2 Å to 2.3 Å within transition metal complexes . This is supported by our recent findings on Sm open‐chain polyarsenides . In [(Cp′′′Co) 2 As 4 Sm( η 5 ‐C 5 Me 5 ) 2 ] (Cp′′′=1,2,4‐tBu 3 C 5 H 2 ), an arsenic chain is coordinated by a [Cp* 2 Sm] + moiety.…”

“…The structural analysis revealed the samarium polyarsenide [(Cp* 2 Sm) 4 As 8 ] ( 2 ), which fills the gap in the realgar‐type [Pn 8 ] 4− polypnictide series (Figure ). Compound 2 is also the largest molecular polyarsenide of the f‐elements ever reported . The composition of 2 was confirmed by elemental analysis and 1 H NMR spectroscopy, which displayed a single resonance at 1.58 ppm attributed to the decamethylcyclopentadienyl units.…”

“…Compound 2 is also the largest molecular polyarsenide of the f-elements ever reported. [5,21,24] Thec omposition of 2 was confirmed by elemental analysis and 1 HNMR spectroscopy,w hich displayed as ingle resonance at 1.58 ppm attributed to the decamethylcyclopentadienyl units.Additionally,IRspectra of 2 are in excellent agreement with those obtained for the lighter phosphorus and the heavier antimony homologue,a s one would expect for analogues complexes.All Sm À As bond lengths are similar and range between Sm1 À As1 3.0814 (10) and Sm3 À As7 3.1734 (10) ,which is only slightly longer than that in 1.W ithin the {As 8 } 4À tetraanion, all AsÀAs bonds are between 2.4044(12) and 2.5003 (12) and therefore single bonds.Angles within the arsenic cage range from 93.52 (4) 4À anion is at ypical Zintl anion, which is isoelectronic to the mineral realgar (As 4 S 4 ) and has asimilar structure.…”

“…[7,20] This is supported by our recent findings on Sm open-chain polyarsenides. [21] In [(Cp'''Co) 2 As 4 Sm(h 5 -C 5 Me 5 ) 2 ] (Cp''' = 1,2,4-tBu 3 C 5 H 2 ), an arsenic chain is coordinated by a[Cp* 2 Sm] + moiety.The As À As distance of the arsenic atoms bonded to Sm accounts for 2.3715 (13) ,i st herefore significantly elongated compared to 1 and more consistent with an AsÀAs single bond. On the other hand, SmÀAs distances are very similar (3.014(1) for 1;2.9606(11) and 2.9815 (11) for the open-chain complex), and therefore almost unaffected by the As À As bond order.…”

Recent Advances in Rare‐Earth Polypnictides

“…Similarly, trinuclear clusters of (Cp”'Co) 2 As 4 Sm(Cp*) 2 have also been prepared using the same synthetic route for the polyphosphide analogue: the reductive dimerization of As 2 entities in (Cp”'Co) 2 (μ,ŋ 2:2 ‐As 2 ) 2 by samarocenes furnished an acyclic As 4 chain (Figure B).…”