Die experimentelle Bestimmung der Elektronendichteverteilung in einem Chrom-Carben- sowie einem Chrom-Carbin-Komplex / The Experimental Determination of the Electronic Deformation Densities in a Chromium Carbene and a Chromium Carbyne Complex

Goddard, Richard; Claus, K. H.

doi:10.1515/znb-1983-1119

Cited by 17 publications

(7 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our model again explains the bias for the anti -isomer in both the free and coordinated carbenes (Table ). These results are also confirmed by neutron diffraction measurements . However, the calculated [C−C]−O distances (1.517 and 1.518 Å for complexes 1 and 15 , respectively) are the expected for a single σ C - C bond.…”

Section: Resultssupporting

confidence: 72%

“…This failure to explain the observed bond shortening by applying an inductive model led us to consider an alternative explanation. In fact, the bond shortening is clearly seen in X-ray diffraction structural determinations, but it is not present in the structure of [pentacarbonyl(ethoxymethyl)carbene]chromium(0) obtained by neutron diffraction . Therefore, it can be thought that the anomalous shortening seen in some ethoxy-carbene complexes may be due to the packing in the crystal.…”

Section: Resultsmentioning

confidence: 99%

“…Furthermore, the [C−C]−O−CCr distance in the crystals is in many cases considerably shorter than expected for a single bond, like for example in CH 3 −CH 2 −OH. One clear exception to this rule is observed in [pentacarbonyl(ethoxymethyl)chromium(0)]carbene, 1 , albeit in this case the measurement was effected by neutron diffraction (Table ).

1 …”

Section: Introductionmentioning

confidence: 97%

See 2 more Smart Citations

Structure and Conformations of Heteroatom-Substituted Free Carbenes and Their Group 6 Transition Metal Analogues

et al. 2004

View full text Add to dashboard Cite

A systematic density functional theory (DFT) study of free and Cr-and W-coordinated alkoxy-carbenes has been carried out. The structure of the free carbenes and their relative energies remains unaltered by coordination to the metal. A clear bias for the anti-isomer is observed in both the free and coordinated carbenes. The exception is complexes having alkynyl substituents. In this case, the metal complex prefers the syn-disposition. The theoretical model explains the observed bias for the anti-isomer by the stabilizing contribution of a stereoelectronic effect due to the two-electron donation from the σ CH orbital of the O-Me group to the π* CO orbital of the CO ligand and feedback donation of the π CO orbital to the σ* CH orbital and the destabilizing repulsion between the groups linked to the carbene carbon. This last factor is the determinant one since the linear triple bond produces a clear bias for the syn-isomer only in the coordinated carbene, showing that the steric contribution rather than the electronic repulsion is responsible for the structure of group 6 Fischer carbenes. The anti-syn isomerization in chromium(0)-carbene complexes has also been studied. This process occurs without affecting either the carbene ligand or the coordination sphere of the metal by rotation of the C(Cr)-O-Me bonds. The developed model is fully applicable to tungsten-carbene complexes.

show abstract

Section: Resultssupporting

confidence: 72%

Section: Resultsmentioning

confidence: 99%

1 …”

Section: Introductionmentioning

confidence: 97%

See 1 more Smart Citation

Structure and Conformations of Heteroatom-Substituted Free Carbenes and Their Group 6 Transition Metal Analogues

et al. 2004

View full text Add to dashboard Cite

show abstract

“…Most new compounds synthesized during the course of this study proved to be amenable to structural study in the solid state by X-ray crystallography. Among these, compound 5 represents, to our knowledge, the first boryl derivatized Fischer carbene complex (although “free” boryl-substituted carbenes and their heavier Group 14 analogues have been reported). , With respect to the metal-carbene interaction, the bonding situation appears to be comparable to known, structurally characterized, alkyl or aryl substituted Fischer carbene complexes such as Cr(CO) 5 {C(OEt)Me} and Cr(CO) 5 {C(OMe)Ph} . Thus, the Cr–C carbene and trans Cr–C(O) distances [2.045(2) and 1.890(2) Å; Figure ] are very similar to those determined for Cr(CO) 5 {C(OEt)Me} [2.053(6) and 1.893(5) Å, respectively] .…”

Section: Results and Discussionmentioning

confidence: 80%

Circumventing Redox Chemistry: Synthesis of Transition Metal Boryl Complexes from a Boryl Nucleophile by Decarbonylation

et al. 2014

View full text Add to dashboard Cite

The very strong reducing capabilities of the boryllithium nucleophile (THF)2Li{B(NDippCH)2} (1, Dipp = 2,6-iPr2C6H3) render impractical its use for the direct introduction of the {B(NDippCH)2} ligand via metathesis chemistry into the immediate coordination sphere of transition metals (d(n), with n ≠ 0 or 10). Instead, 1 typically reacts with metal halide, amide and hydrocarbyl electrophiles either via electron transfer or halide abstraction. Evidence for the formation of M-B bonds is obtained only in the case of the d(5) system [{(HCDippN)2B}Mn(THF)(μ-Br)]2. Lower oxidation state metal carbonyl complexes such as Fe(CO)5 and Cr(CO)6 react with 1 via nucleophilic attack at the carbonyl carbon atom to give boryl-functionalized Fischer carbene complexes Fe(CO)4{C(OLi(THF)3)B(NDippCH)2} and Cr(CO)5{C(OLi(THF)2)B(NDippCH)2}. Although C-to-M boryl transfer does not occur for these formally anionic systems, more labile charge neutral bora-acyl derivatives of the type LnM{C(O)B(NDippCH)2} [LnM = Mn(CO)5, Re(CO)5, CpFe(CO)2] can be synthesized, which cleanly lose CO to generate M-B bonds. From a mechanistic standpoint, an archetypal organometallic mode of reactivity, carbonyl extrusion, has thus been shown to be applicable to the boryl ligand class, with (13)C isotopic labeling studies confirming a dissociation/migration pathway. These proof-of-methodology synthetic studies can be extended beyond boryl complexes of the group 7 and 8 metals (for which a number of versatile synthetic routes already exist) to provide access to complexes of cobalt, which have hitherto proven only sporadically accessible.

show abstract

“…The complexes have a ring C−H ortho to the carbene lying staggered with respect to two adjacent carbonyl ligands and in close contact with them, leading to somewhat strained sp 2 angles in the range 122.9(2)−127.3(3)° for angle 2, compared to the Cr−C−C bond angle of ca. 121° for the sterically undemanding substituted complex [Cr(CO) 5 {C(OEt)Me}] . In contrast, the moiety bonded to the carbene via the oxygen atom results in marked differences in the geometry around the carbene carbon atom.…”

Section: Resultsmentioning

confidence: 99%

Steric and Electronic Effects of Metal-Containing Substituents in Fischer Carbene Complexes of Chromium

et al. 2008

View full text Add to dashboard Cite

The Fischer carbene complexes of chromium pentacarbonyl with one or two different metal-containing substituents were synthesized and studied in solution and in the solid state. The dimetallic complexes [Cr(CO) 5 {C(OTiCp 2 Cl)(2-BT)}] (2) (BT ) benzo[b]thienyl) and [Cr(CO) 5 {C(OEt)((η 6 -2-BT)Cr(CO) 3 )}] (3) and trimetallic complexes [Cr(CO) 5 {C(OTiCp 2 Cl)((η 6 -2-BT)Cr(CO) 3 )}] (4) and [Cr(CO) 5 {C(OTiCp 2 -Cl)Fc}] (5) (Fc ) ferrocenyl) were prepared and systematically studied with respect to the reference complex [Cr(CO) 5 {C(OEt)(2-BT)}] (1) for the importance of the metal substituents in influencing carbene ligand reactivity. It was clear from the crystal structure determination of 4 that most of the unoccupied space was found around the benzo[b]thienyl substituent. Hence, it was also possible to synthesize the analogous more crowded trimetallic carbene complex 5 containing an electron-donating ferrocenyl instead of the [Cr(η 6 -2-BT)(CO) 3 ] substituent. Dilithiated ferrocene reacts with 2 equiv of chromium hexacarbonyl, which after alkylation with Et 3 OBF 4 affords the ferrocen-1,1′-diyl-bridged biscarbene [(Cr(CO) 5 ) 2 {µ 2 -C 2 (OEt) 2 Fe(C 5 H 4 ) 2 -C,C′)}] (7), while metalation with TiCp 2 Cl 2 resulted in the formation of the novel ferrocene-titanocene-bridged biscarbene complex [(Cr(CO) 5 ) 2 {µ 2 -C 2 (O 2 TiCp 2 -O,O′)(Fe(C 5 H 4 ) 2 -C,C′)}] (6).

show abstract

Die experimentelle Bestimmung der Elektronendichteverteilung in einem Chrom-Carben- sowie einem Chrom-Carbin-Komplex / The Experimental Determination of the Electronic Deformation Densities in a Chromium Carbene and a Chromium Carbyne Complex

Cited by 17 publications

References 8 publications

Structure and Conformations of Heteroatom-Substituted Free Carbenes and Their Group 6 Transition Metal Analogues

Structure and Conformations of Heteroatom-Substituted Free Carbenes and Their Group 6 Transition Metal Analogues

Circumventing Redox Chemistry: Synthesis of Transition Metal Boryl Complexes from a Boryl Nucleophile by Decarbonylation

Steric and Electronic Effects of Metal-Containing Substituents in Fischer Carbene Complexes of Chromium

Contact Info

Product

Resources

About