scholarly journals Synthesis, Characterization and Reactivity of Chromium(VI) Alkylidenes

2019 ◽  
Author(s):  
Pengcheng Wu ◽  
Glenn P. A. Yap ◽  
Klaus Theopold
Keyword(s):  
Ligand Substitution ◽  
X Ray Diffraction ◽  
Substitution Reactions ◽  
X Ray ◽  
Chromium Vi ◽  
Organic Products ◽  
Ligand Substitution Reactions

Chromium(VI) dialkyls are remarkably acidic, yielding a new set of anionic chromium alkylidenes upon deprotonation with KN(TMS)<sub>2</sub>. We describe the characterization of three anionic chromium alkylidenes of the type [(ArN)<sub>2</sub>Cr(=CHR)(CH<sub>2</sub>R]<sup>-</sup> (R = <i><sup>t</sup></i>Bu, SiMe<sub>3</sub>, Ph; Ar = 2,6-diisopropylphenyl). NEt<sub>4</sub>[(ArN)<sub>2</sub>Cr(=CHSiMe<sub>3</sub>)(CH<sub>2</sub>SiMe<sub>3</sub>)] has been structurally characterized by X-ray diffraction. We have also studied the C-H activation of cyclohexane effected by the transient neopentylidene (ArN)<sub>2</sub>Cr(=CHCMe<sub>3</sub>). This reaction generated a tri-nuclear chromium(IV) complex, namely ‘[Cr(NAr)<sub>2</sub>]<sub>3</sub>’, as well as the two organic products cyclohexene and neopentane. A probable intermediate in this reaction could be trapped by PPh<sub>3</sub> to form (ArN)<sub>2</sub>Cr(PPh<sub>3</sub>)<sub>2</sub>. The latter undergoes ligand substitution reactions with ethylene and CO to produce p-acid complexes of tetravalent chromium.

scholarly journals Synthesis, Characterization and Reactivity of Chromium(VI) Alkylidenes

2019 ◽  
Author(s):  
Pengcheng Wu ◽  
Glenn P. A. Yap ◽  
Klaus Theopold
Keyword(s):  
Ligand Substitution ◽  
X Ray Diffraction ◽  
Substitution Reactions ◽  
X Ray ◽  
Chromium Vi ◽  
Organic Products ◽  
Ligand Substitution Reactions

Chromium(VI) dialkyls are remarkably acidic, yielding a new set of anionic chromium alkylidenes upon deprotonation with KN(TMS)<sub>2</sub>. We describe the characterization of three anionic chromium alkylidenes of the type [(ArN)<sub>2</sub>Cr(=CHR)(CH<sub>2</sub>R]<sup>-</sup> (R = <i><sup>t</sup></i>Bu, SiMe<sub>3</sub>, Ph; Ar = 2,6-diisopropylphenyl). NEt<sub>4</sub>[(ArN)<sub>2</sub>Cr(=CHSiMe<sub>3</sub>)(CH<sub>2</sub>SiMe<sub>3</sub>)] has been structurally characterized by X-ray diffraction. We have also studied the C-H activation of cyclohexane effected by the transient neopentylidene (ArN)<sub>2</sub>Cr(=CHCMe<sub>3</sub>). This reaction generated a tri-nuclear chromium(IV) complex, namely ‘[Cr(NAr)<sub>2</sub>]<sub>3</sub>’, as well as the two organic products cyclohexene and neopentane. A probable intermediate in this reaction could be trapped by PPh<sub>3</sub> to form (ArN)<sub>2</sub>Cr(PPh<sub>3</sub>)<sub>2</sub>. The latter undergoes ligand substitution reactions with ethylene and CO to produce p-acid complexes of tetravalent chromium.

Ligand Substitution Reactions of the Nickel-Sulphur Cluster [Ni3(μ3-S)2(PEt3)6]2+. X-Ray Crystal Structure of [Ni3(μ3-S)2(PEt3)2(S2CNEt2)2]

1991 ◽  
Vol 46 (9) ◽  
pp. 1161-1164 ◽  
Author(s):  
Franco Cecconi ◽  
Carlo A. Ghilardi ◽  
Stefano Midollini ◽  
Annabella Orlandini
Keyword(s):  
Molecular Structure ◽  
Crystal Structure ◽  
Single Crystal ◽  
Inner Core ◽  
Ligand Substitution ◽  
Diphosphine Ligands ◽  
X Ray Diffraction ◽  
Substitution Reactions ◽  
Space Group ◽  
X Ray

Compounds of the type [Ni3S2(PR3)6]X2 (R = Me, Et; X = BPh4, ClO4) react with dithiocarbamate and diphosphine ligands to yield products [Ni3S2(PEt3)2(S2CNEt2)2] (1), [Ni3S2(PMe3)2(S2CNEt2)2] (2), and [Ni3S2(PMe3)2(dppe)2][BPh4]2 (3). The molecular structure of 1 has been established by single crystal X-ray diffraction. Space group C2/c, a = 25.137(3), b = 9.084(1), c = 18.333(2) Å, β = 123.41(2)°, Ζ = 4, 1128 observed unique reflections, R = 0.041. The inner core of 1 consists of a triangle of nickel atoms capped by two triply bridging sulphur ligands.

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