Alkinylverbindungen von Übergangsmetallen, XXX<sup>1)</sup> Hexaalkinylcobaltate(II)

Nast, R.; Fock, Kurt

doi:10.1002/cber.19761090206

Cited by 14 publications

(2 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thus, homoleptic derivatives with formulæ [Li(THF) 4 ][Co II (Mes) 3 ] (Mes = mesityl), [Li(THF) 2 ] 2 [Co II {( o -C 6 H 4 ) 2 O-κ 2 C } 2 ], Li 2 [Co II {C 6 H 3 (OMe) 2 -2,6} 4 ]·3THF, and [Li(tmen)] 2 [Co II R 4 ] (R = Me, CH 2 SiMe 3 ; tmen = N , N , N′ , N ′-tetramethylethane-1,2-amine) were obtained by reaction of CoX 2 with the corresponding LiR in excess . Compounds with even higher degree of substitution are achieved using sodium or potassium alkynyls, QCCR, a method used to prepare different salts of the apparently six-coordinate [Co(CCR) 6 ] 4– anions (R = H, Me, Ph, , Cy).…”

Section: Resultsmentioning

confidence: 99%

Homoleptic Organocobalt(III) Compounds with Intermediate Spin

et al. 2014

View full text Add to dashboard Cite

Homoleptic organocobalt(III) compounds with formula [NBu4][Co(III)(C6X5)4] [X = F (3), Cl (4)] were obtained in reasonable yields by chemical oxidation of the corresponding divalent species [NBu4]2[Co(II)(C6X5)4] [X = F (1), Cl (2)]. The [Co(III)(C6X5)4](-)/[Co(II)(C6X5)4](2-) couples are electrochemically related by quasi-reversible, one-electron exchange processes at moderate potential: E1/2 = -0.29 (X = F) and -0.36 V (X = Cl) versus saturated calomel electrode. The [Co(III)(C6X5)4](-) anions in salts 3 and 4 show an unusual square-planar geometry as established by single-crystal X-ray diffraction methods. According to their stereochemistry, these Co(III) derivatives (d(6)) are paramagnetic non-Kramers systems with a large zero-field splitting contribution and no observable electron paramagnetic resonance (EPR) spectrum. The thermal dependence of their magnetic susceptibilities can be explained in terms of a spin-Hamiltonian formalism with S = 1 ground state (intermediate spin) and substantial spin-orbit contribution. The magnetic properties of the square-planar d(7) parent species [NBu4]2[Co(II)(C6X5)4] were also thoroughly studied both at microscopic (EPR) and macroscopic levels (alternating current and direct current magnetization measurements). They behave as S = 1/2 (low spin) systems with mainly (dz(2))(1) electron configuration and a certain degree of s-orbital admixture that has been quantified. The electronic structures of all four open-shell [Co(C6X5)4](q-) compounds (q = 1, 2) accounting for their respective magnetic properties are based on a common orbital energy-level diagram.

show abstract

Section: Resultsmentioning

confidence: 99%

Homoleptic Organocobalt(III) Compounds with Intermediate Spin

et al. 2014

View full text Add to dashboard Cite

show abstract

“…4 Although certain analogous acetylide complexes [M(CtCR) 6 ] n-(R ) H, Me, or Ph) have long been known, 5 they are reported as highly unstable and/or insoluble salts, ill-suited for use in subsequent bridge-forming reactions. Complexes of this type are known for M ) Cr III , 6 Mn III , 7 Fe II , 8 Fe III , 8 Co II , 9 and Co III , 10 with the only difference in stoichiometry, color, and magnetism from the hexacyano species corresponding to the existence of high-spin [Co(CCR) 6 ], 4-9 as opposed to low-spin [Co(CN) 4 ] 2and [Co(CN) 5 ] 3-. 11, 12 A similar parallel to cyanide chemistry occurs for the late transition metals, for which the complexes [M(CCR) 4 ] 2-(M ) Ni, Pd, Pt) are diamagnetic and presumably square planar, 13 the complexes [M(CCR) 2 ] -(M ) Cu, Ag, Au) are presumably linear, 14 and the complexes [M(CCR) 4 ] 2-(M ) Zn, Cd, Hg) are tetrahedral.…”

Section: Introductionmentioning

confidence: 99%

Homoleptic Trimethylsilylacetylide Complexes of Chromium(III), Iron(II), and Cobalt(III): Syntheses, Structures, and Ligand Field Parameters

Berben

Long

2005

Inorg. Chem.

View full text Add to dashboard Cite

A straightforward method for synthesizing soluble homoleptic trimethylsilylacetylide complexes of first-row transition metal ions is presented. Reaction of anhydrous CrCl2 with an excess of LiCCSiMe3 in THF at -25 degrees C affords orange Li3[Cr(CCSiMe3)6].6THF (1), while analogous reactions employing M(CF3SO3)2 (M = Fe or Co) generate pale yellow Li4[Fe(CCSiMe3)6].4LiCCSiMe3.4Et2O (2) and colorless Li3[Co(CCSiMe3)6].6THF (3). Slightly modified reaction conditions lead to Li8[Cr2O4(CCSiMe3)6].6LiCCSiMe3.4glyme (4), featuring a bis-mu-oxo-bridged binuclear complex, and Li3[Co(CCSiMe3)5(CCH)].LiCF3SO3.8THF (5). The crystal structures of 1-3 show the trimethylsilylacetylide complexes to display an octahedral coordination geometry, with M-C distances of 2.077(3), 1.917(7)-1.935(7), and 1.908(3) angstroms for M = Cr(III), Fe(II), and Co(III), respectively, and nearly linear M-C[triple bond]C angles. The UV-visible absorption spectrum of [Cr(CCSiMe3)6]3- in hexanes exhibits one spin-allowed d-d transition (4T2g <-- 4A1g) and three lower-energy spin-forbidden d-d transitions. The spectra of [Fe(CCSiMe3)6]4- and [Co(CCSiMe3)6]3- in acetonitrile display high-intensity charge-transfer bands, which obscure all d-d transitions except for the lowest-energy spin-allowed band (1T1g <-- 1A1g) of the latter complex. Time-dependent density functional theory (TD-DFT) calculations were employed as an aide in assigning the observed transitions. Taken together, the results are most consistent with the ligand field parameters delta(o) = 20,200 cm(-1) and B = 530 cm(-1) for [Cr(CCSiMe3)6]3-, delta(o) = 32 450 cm(-1) and B = 460 cm(-1) for [Fe(CCSiMe3)6]4- and delta(o) = 32 500 cm(-1) and B = 516 cm(-1) for [Co(CCSiMe3)6]3-. Ground-state DFT calculations support the conclusion that trimethylsilylacetylide acts as a pi-donor ligand.

show abstract