Strukturuntersuchungen an organochrom-verbindungen I. IR-und röntgen-strukturanalyse des Li4Cr2(CH3)8 4 C4H8O

Krausse, J.; Marx, G.; Schödl, G.

doi:10.1016/s0022-328x(00)90607-7

Cited by 90 publications

(32 citation statements)

References 14 publications

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“…The results from this analysis suggest the initial chromium complex has undergone complete alkylation to lose the PNP ligand and form a short Cr-Cr multiple bond. The refined Cr-Cr bond length (2.01(2) Å) is close to that reported for the quadruple bond in the Cr(II) salt Li 4 [Cr 2 Me 8 )]Ŋ4THF, 25 …”

Section: Effect Of [Ph 3 C][al{ocsupporting

confidence: 79%

Activation of [CrCl₃{PPh₂N(ⁱPr)PPh₂}] for the selective oligomerisation of ethene: a Cr K-edge XAFS study

Bartlett

Moulin

Tromp

et al. 2016

Catal. Sci. Technol.

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The activation of the ethene tetramerisation catalyst system based upon [CrCl3(THF)3] and N( i Pr)(PPh2)2 has been investigated in situ via the reaction of [CrCl3{PPh2N(R)PPh2}(THF)] 1a (R= i Pr) with excess AlMe3 in toluene. The Cr K-edge XAFS spectrum of the solution freeze quenched after 1 min reaction time indicated monomethylation of the metal with the resultant product being [CrClMe(ClAlCl3){PPh2N(R)PPh2}(THF)] 4a (R= i Pr). After 5 minutes reaction time the XAFS spectra indicate that ~50% of 4a had been converted to a Cr(II) species, with the central core being high spin [CrCl2{PPh2N(R)PPh2}] 7a (R= i Pr); a similar species, [CrClMe{PPh2N(R)PPh2}] 9a (R= i Pr) was observed as its adduct with AlMe3 (10a) (R= i Pr) when spectra were recorded on samples maintained a room temperature. Detailed analysis (EXAFS and XANES) indicated that 7a and 9a are stabilised by adduct formation of a Cr-Cl bond to the Lewis acids B(C6F5)3 and AlMe3, respectiveley. Modelling with DFT methods indicated that five-coordination was achieved, respectively by Cr-F (11a) and Cr-C (10a) interactions. In the presence of [Ph3C][Al{OC( t Bu F )3}4], the Cr XAFS of the room temperature solution was inconsistent with the maintenance of a phosphine complex, but could be modelled with a site like [Cr2Me8] 4-{Cr-Cr 2.01 (2), Cr-C 2.14(4)}, thus demonstrating considerable variation in the effects of differing Lewis acids.

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Section: Effect Of [Ph 3 C][al{ocsupporting

confidence: 79%

Activation of [CrCl₃{PPh₂N(ⁱPr)PPh₂}] for the selective oligomerisation of ethene: a Cr K-edge XAFS study

Bartlett

Moulin

Tromp

et al. 2016

Catal. Sci. Technol.

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“…3 4 ], have been reported and their structures described. [97][98][99] Both contain eclipsed Cr-C 4 sets of bonds, and the Cr-Cr distances are 1.980(5) and 1.975(5) Å. These structures clearly imply the presence of Cr-Cr quadruple bonds.…”

Section: Compounds With Cr-c Bondsmentioning

confidence: 89%

Chromium Compounds

Cotton

Multiple Bonds Between Metal Atoms

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“…Li,Cr,(CH,),(THF), erstmals von KURRAS und OTTO beschrieben wurde[27]. Kristallstrukturuntersuchungen ergaben au5erordentlich kurze Cr-Cr-Abstande von 0,198 nm in Zweikernstrukturen[28,29]. Durch die Chrom-Chrom-Vierfachbindung kommt es zur Spinkompensation der monomeren d4-Systeme, die den Diamagnetismus der dimeren Komplexe erklart.…”

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Butadienpolymerisation Mit σ‐Organochromverbindungen

Schmiedeknecht¹,

Hartung²,

Heublein³

et al. 1984

Acta Polymerica

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Herrn Professor Dr. habil. Joachim Ulbricht zum 60. Geburtstag gewidmeta-Organochromverbindungen, die eine freie Koordinationsstelle am Chrom besitzen, konnen als homogene Katalysatoren zur Butadienpolymerisation verwendet werden. Wahrend fiinffach koordinierte Organochrom(II1)-Verbindungen erst nach langerer Inkubationszeit polymerisationsaktiv sind, beginnt die Polymerisation in Gegenwart von Organochrom( 11)-Verbindungen sofort. Da durch diese Verbindungen Olefine nicht polymerisiert werden, bieten sie die Moglichkeit, eine selektive Butadienpolymerisation aus C4-Kohlenwasserstoffgemiscben zu initiieren. 17oJcu.wpuaayzuc 6ymaduena e npucymcmsuu a-xpo,nopzanuwcmx coeauneHuiiU-XpOMOpI' aHUYeCKHe COeAHHeHHR, HMeIoqHe CBO60fiHOe HOOpAHHaqHOHHOe MeCTO H a aTOMe XpOMa, MOrYT 6bITb HCIlOJlb30BaHbI B KaqeCTBe OAHOPOAHMX KaTaJIH8aTOpOB AJIH nOJrUMepHaaI(HH6yTmHeHa. b T H K P a T H 0 KOOPAHHHPO-BaHHbIe XpOMOpraHHqeCKHe COeAHHeHHR TpeXBaJIeHTHOrO XpOMa CnOC06CTByIoT IIOJIHMepH3aqHH TOJlbKO ~e p e 3 AJlHTeJIbHOe HHKY6aqHOHHOe BpeMR, B TO BpeMH KPK B nPHCYTCTBHli COeAHHeHHfi ABYXBaJIeHTHOrO XpOMa IIOJIHMepH-3 a q~a HawmaeTca cpasy. IlocKonbKy y~a 3 a~~~e coenmHeHm He I I O J I H M~~H~~I O T one@iHu, HX npmeHeHne 1103-BOJIIieT HHHqHHpOBaTb CeJIeKTHBHYIo nOJIHMepH3aqHIo 6yTmHeHa Ha CMeCefi C4-yi'JIeBO~OpOAOB.Polymerization of butadiene with u-organochromium compounds a-Organochromium compounds with a free coordination position at the chromium atom can be used as homogeneous catalysts for the polymerization of butadiene. Whereas fivefold coordinated organochromium(II1)-compounds are active in polymerizations only after a long induction period, the polymerization starts immediately in the presence of organochromium( 11)-compounds. As olefins are not polymerized by these compounds, they offer the possibility to initiate a selective polymerization of butadiene out of C, hydrocarbon mixtures.

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Strukturuntersuchungen an organochrom-verbindungen I. IR-und röntgen-strukturanalyse des Li4Cr2(CH3)8 4 C4H8O

Cited by 90 publications

References 14 publications

Activation of [CrCl₃{PPh₂N(ⁱPr)PPh₂}] for the selective oligomerisation of ethene: a Cr K-edge XAFS study

Activation of [CrCl₃{PPh₂N(ⁱPr)PPh₂}] for the selective oligomerisation of ethene: a Cr K-edge XAFS study

Chromium Compounds

Butadienpolymerisation Mit σ‐Organochromverbindungen

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Strukturuntersuchungen an organochrom-verbindungen I. IR-und röntgen-strukturanalyse des Li4Cr2(CH3)8 4 C4H8O

Cited by 90 publications

References 14 publications

Activation of [CrCl3{PPh2N(iPr)PPh2}] for the selective oligomerisation of ethene: a Cr K-edge XAFS study

Activation of [CrCl3{PPh2N(iPr)PPh2}] for the selective oligomerisation of ethene: a Cr K-edge XAFS study

Chromium Compounds

Butadienpolymerisation Mit σ‐Organochromverbindungen

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Activation of [CrCl₃{PPh₂N(ⁱPr)PPh₂}] for the selective oligomerisation of ethene: a Cr K-edge XAFS study

Activation of [CrCl₃{PPh₂N(ⁱPr)PPh₂}] for the selective oligomerisation of ethene: a Cr K-edge XAFS study