Browsing by Author "Theopold, Klaus H."
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Item Cr−Cr Quintuple Bonds: Ligand Topology and Interplay Between Metal−Metal and Metal−Ligand Bonding(American Chemical Society, 2015-10-26) Falceto, Andrés; Theopold, Klaus H.; Alvarez, Santiago; Andrés Falceto, Klaus H. Theopold, and Santiago Alvarez; Theopold, Klaus H.Chromium–chromium quintuple bonds seem to be approaching the lower limit for their bond distances, and this computational density functional theory study tries to explore the geometrical and electronic factors that determine that distance and to find ways to fine-tune it via the ligand choice. While for monodentate ligands the Cr–Cr distance is predicted to shorten as the Cr–Cr–L bond angle increases, with bridging bidentate ligands the trend is the opposite, since those ligands with a larger number of spacers between the donor atoms favor larger bond angles and longer bond distances. Compared to Cr–Cr quadruple bonds, the quintuple bonding in Cr2L2 compounds (with L a bridging bidentate N-donor ligand) involves a sophisticated mechanism that comprises a positive pyramidality effect for the σ and one π bond, but a negative effect for one of the δ bonds. Moreover, the shorter Cr–Cr distances produce a mismatch of the bridging ligand lone pairs and the metal acceptor orbitals, which results in a negative correlation of the Cr–Cr and Cr–N bond distances in both experimental and calculated structures.Item Mechanism-based design of labile precursors for chromium(I) chemistry(Royal Society of Chemistry, 2015-08-27) Akturk, Eser S.; Yap, Glenn P. A.; Theopold, Klaus H.; Eser S. Akturk, Glenn P. A. Yap and Klaus H. Theopold; Akturk, Eser Sahin; Yap, Glenn P. A.; Theopold, Klaus H.Dinitrogen complexes of the type TpR,RCr–N2–CrTpR,R are not the most labile precursors for Cr(I) chemistry, as they are sterically protected from obligatory associative ligand substitution. A mononuclear alkyne complex – TptBu,MeCr(g2-C2(SiMe3)2) – proved to be much more reactive.Item A molecular substitutional disorder case study suitable for instruction: L2CrII(THF)/L2[(trimethylsilyl)methyl]CrIII (L is 2,5-bis{[(2,6-diisopropylphenyl)imino]methyl}pyrrol-1-ide)(Acta Crystallographica Section C: Structural Chemistry, 2022-04-06) Salisbury, Brian A.; Young, John F.; Theopold, Klaus H.; Yap, Glenn P. A.A solution of CrII and CrIII complexes, bis(2,5-bis{[(2,6-diisopropylphenyl)imino]methyl}pyrrol-1-ido)(tetrahydrofuran)chromium(II)–bis(2,5-bis{[(2,6-diisopropylphenyl)imino]methyl}pyrrol-1-ido)[(trimethylsilyl)methyl]chromium(III) (0.88/0.12), [Cr(C30H38N3)2(C4H8O)]0.88[Cr(C30H38N3)2(C4H11Si)]0.12 or L2CrII(THF)/L2[(trimethylsilyl)methyl]CrIII (L = 2,5-bis{[(2,6-diisopropylphenyl)imino]methyl}pyrrol-1-ide and THF is tetrahydrofuran), in pentane crystallizes in the monoclinic space group P21/c. The structure obtained shows most of the atoms coincident but with THF disordered with the (trimethylsilyl)methyl ligand. Structures with this disorder, involving more than two or three atoms, seem to appear rarely in the literature; however, in this case, the data set is ideal for the crystallographic instruction of molecular substitution disorder.Item Synthesis, Characterization, and Reactivity of Tris(imido)chromium(VI) Complexes(Inorganic Chemistry, 2023-11-27) Wu, Pengcheng; Yap, Glenn P. A.; Theopold, Klaus H.Multiple tris(imido)chromium(VI) complexes, including neutral and ionic compounds, have been synthesized and characterized. (tBuN)2Cr(NHtBu)Cl can be deprotonated by KN(SiMe3)2, yielding K[(tBuN)3CrCl]. This tris(imido) anion undergoes nucleophilic substitution by PPh3 and tBuNH2 to form (tBuN)3Cr(PPh3) and (tBuN)2Cr(NHtBu)2, respectively. (tBuN)2Cr(NHtBu)2 loses one amido proton to form K[(tBuN)3Cr(NHtBu)] upon reaction with KN(SiMe3)2. The imido ligands of K[(tBuN)3CrCl] and (tBuN)3Cr(PPh3) are attacked by the electrophile MeI to produce (tBuN)2Cr(NMetBu)Cl and (tBuN)2Cr(NMetBu)I, respectively. An alternate way to make tris(imido) anions is deprotonation of (tBuN)2Cr(NHtBu)Cl by an alkyl lithium reagent, e.g., Me3SiCH2Li. The resulting Li[(tBuN)3CrCl] was alkylated by a second equivalent of Me3SiCH2Li to form Li[(tBuN)3Cr(CH2SiMe3)]. Reactivity studies of tris(imido) complexes show cycloaddition with PhNCO or CO2 to form metallacycles.