Bis(tetraisopropylcyclopentadienylnickel)dichalcogenides:  Complexes of the Novel [{CpME}₂] Type (E = S, Se, Te)

Abstract

The dinuclear dichalcogenides [{(C 5 HR 4 )NiE} 2 ] (R ) CHMe 2 ; E ) S (2), Se (3), Te (4)) have been synthesized from [{(C 5 HR 4 )NiBr} 2 ] (1) (R ) CHMe 2 ) and the corresponding disodium dichalcogenides. Crystal structure analyses show four-membered Ni 2 E 2 rings with weak, but significant E‚‚‚E interaction. 1-4 were characterized electrochemically and reveal nickel-centered oxidations, bridging ligand-centered reductions, and the formation of mixedvalent Ni(II)/Ni(III) species.

Bis(η-tert-butylcyclopentadienyl)hydridoniobium Ditelluride, a Convenient Reagent for the Synthesis of Polynuclear Metal Telluride Complexes

“…In complex 5 each Nb center is surrounded by two CpЈ anions and two Te 2Ϫ bridges. A bonding interaction between opposite atoms Te(1) and Te(1Ј) [d ϭ 4.262(1) Å ] was excluded [25] in agreement with literature values given for planar M 2 Te 2 rings: Whereas in the Ni 2 Te 2 cycle of [(iPr 4 C 5 H) 2 Ni 2 (µ-Te) 2 ] the observed Te···Te distance of 3.052(5) Å has been ascribed to a bond order of nearly one, [26] a clearly nonbonding situation has been found in [CpЈ 4 Zr 2 Te 2 ] [d(Te···Te) ϭ 4.006(1) Å ]. [21] Less evident is the interpretation of the Nb(1)···Nb(1Ј) distance in 5.…”

X‐ray Absorption Spectroscopic, Crystallographic, Theoretical (DFT) and Chemical Evidence for a Chalcogen–Chalcogen Two‐Center/Three‐Electron Half Bond in an Unprecedented “Subselenide” Se23− Ligand

“…Herein we present compelling experimental/theoretical evidence that the known neutral compound (Cp′Ni) 2 (μ 2 ‐Se 2 ) ( 1 , Cp′=1,2,3,4 tetraisopropylcyclopentadiene)7 may be formulated electronically to have a half‐bonded “subselenide” Se 2 3− ligand. This unprecedented assignment necessitates formulation as a mixed‐valent Ni II /Ni III compound that is delocalized (average oxidation state, +2.5); DFT calculations accord with this formulation and the compound’s diamagnetism.…”

“…Noteworthy is that the half‐bonded (2c/3e) Se 2 3− ligand may be viewed as possessing a “net” one‐electron chalcogen–chalcogen bonding interaction involving two bonding and one antibonding electrons (σ 2 σ* 1 ), similar to H 2 − or He 2 + . Based upon the comprehensive electrochemical analysis of 1 by Sitzmann and co‐workers,7 who synthesized and determined room‐temperature X‐ray crystal structures of the Se and corresponding S and Te dimers,7 we report chemical oxidation and reduction of 1 , which led to the isolation and crystallographic characterization of the new one‐electron oxidized [(Cp′Ni) 3 (Se 2 ) 2 ] + BF 4 − ( 2 ) and reduced [Cp* 2 Co][(Cp 2 ′Ni) 2 (μ 2 ‐Se 2 )] ( 3 ).…”

Iron‐Mediated Coupling of Two Ethyl Anions to Form a 2‐Butyne Ligand

“…The Fe–Fe distance of 2.3022(9) Å is much shorter than Fe–Fe single bonds (typically ca. 2.50–2.70 Å) 21. It is even shorter than most Fe–Fe double bonds, which may be as long as the 2.44 Å distance calculated for the carbonyl complex [Fe 2 (CO) 6 (μ,η 1 :η 1 ‐CF 2 )(μ,η 1 :η 2 ‐CO)] 30.…”

“…Moreover, the ditelluride [( 4 CpNi) 2 (μ‐Te 2 )] described in the same publication shows a very similar structure (Table 1). 21…”