1,2‐Addition of Diethylzinc to a Bis(Imidazolyl)ketone Ligand

Folkertsma, Emma; Benthem, S. H.; Jastrzebski, Johann T. B. H.; Lutz, Martin; Moret, Marc‐Etienne; Gebbink, Robertus J. M. Klein

doi:10.1002/ejic.201701363

Cited by 3 publications

(2 citation statements)

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“…Molecule 27 complements the group with organometallic compounds. As recently reported, Fe and Zn templated pinacol-type coupling leads to dinuclear metal complexes with ultra long central C−C bonds (R > 1.7 Å) being clamped by the organometallic framework [ 32 , 130 ]. For the diiron(II) bis(1-methyl-4,5-diphenylimidazolyl)pinacolate bis-chlorido complex a central C−C bond length of 1.730 Å was confirmed by both Xray structure and DFT calculations [ 32 ], which is much longer than a usual pinacolate type C−C [ 131 ].…”

Section: Results and Discussionmentioning

confidence: 99%

Exceptionally Long Covalent CC Bonds—A Local Vibrational Mode Study

et al. 2021

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For decades one has strived to synthesize a compound with the longest covalent C-C bond applying predominantly steric hindrance and/or strain to achieve this goal. On the other hand electronic effects have been added to the repertoire, such as realized in the electron deficient ethane radical cation in its D3d form. Recently, negative hyperconjugation effects occurring in diamino-o-carborane analogs such as di-N,N-dimethylamino-o-carborane have been held responsible for their long C-C bonds. In this work we systematically analyzed CC bonding in a diverse set of 53 molecules including clamped bonds, highly sterically strained complexes such as diamondoid dimers, electron deficient species, and di-N,N-dimethylamino-o-carborane to cover the whole spectrum of possibilities for elongating a covalent C-C bond to the limit. As a quantitative intrinsic bond strength measure, we utilized local vibrational CC stretching force constants ka(CC) and related bond strength orders BSO n(CC), computed at the ωB97X-D/aug-cc-pVTZ level of theory. Our systematic study quantifies for the first time that whereas steric hindrance and/or strain definitely elongate a C-C bond, electronic effects can lead to even longer and weaker C-C bonds. Within our set of molecules the electron deficient ethane radical cation, in D3d symmetry, acquires the longest C-C bond with a length of 1.935 Å followed by di-N,N-dimethylamino-o-carborane with a bond length of 1.930 Å. However, the C-C bond in di-N,N-dimethylamino-o-carborane is the weakest with a BSO n value of 0.209 compared to 0.286 for the ethane radical cation; another example that the longer bond is not always the weaker bond. Based on our findings we provide new guidelines for the general characterization of CC bonds based on local vibrational CC stretching force constants and for future design of compounds with long C-C bonds.

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Section: Results and Discussionmentioning

confidence: 99%

Exceptionally Long Covalent CC Bonds—A Local Vibrational Mode Study

et al. 2021

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“…Furthermore, self-initiated polymeriz-ation of εCL by Zn(C 6 F 5 ) 2 or Al(C 6 F 5 ) 3 have been reported to yield low number average molecular weight polymers attributed to uncontrolled side reactions. 3,6,7 It should be noted that ZnEt 2 has very diverse chemical features and has been used for the addition of alcohols to carbodiimides, 26 reductions of imines, 27 reduction and nucleophilic addition of and to ketones and aldehydes, [28][29][30][31] reduction of acylsilanes, 32 and deprotonation of β-keto esters, 33 clearly testifying to its high and diverse reactivity. In addition, when we tried to employ ZnEt 2 to synthesise cyclic poly(εCL), ZnEt 2 was found proficient in the self-initiated ring-opening polymerization of εCL without requiring any additional initiator (Table S1, † entries 1 and 2) which is in agreement with literature.…”

Section: Introductionmentioning

confidence: 99%