Dataset Information

Unsupported Mg-Alkene Bonding.

ABSTRACT: The first intermolecular early main group metal-alkene complexes were isolated. This was enabled by using highly Lewis acidic Mg centers in the Lewis base-free cations (^Me BDI)Mg⁺ and (^tBu BDI)Mg⁺ with B(C₆ F₅ )₄ ^- counterions (^Me BDI=CH[C(CH₃ )N(DIPP)]₂ , ^tBu BDI=CH[C(tBu)N(DIPP)]₂ , DIPP=2,6-diisopropylphenyl). Coordination complexes with various mono- and bis-alkene ligands, typically used in transition metal chemistry, were structurally characterized for 1,3-divinyltetramethyldisiloxane, 1,5-cyclooctadiene, cyclooctene, 1,3,5-cycloheptatriene, 2,3-dimethylbuta-1,3-diene, and 2-ethyl-1-butene. In all cases, asymmetric Mg-alkene bonding with a short and a long Mg-C bond is observed. This asymmetry is most extreme for Mg-(H₂ C=CEt₂ ) bonding. In bromobenzene solution, the Mg-alkene complexes are either dissociated or in a dissociation equilibrium. A DFT study and AIM analysis showed that the C=C bonds hardly change on coordination and there is very little alkene?Mg electron transfer. The Mg-alkene bonds are mainly electrostatic and should be described as Mg²⁺ ion-induced dipole interactions.

SUBMITTER: Thum K

PROVIDER: S-EPMC7898539 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Unsupported Mg-Alkene Bonding.

Thum Katharina K Friedrich Alexander A Pahl Jürgen J Elsen Holger H Langer Jens J Harder Sjoerd S

Chemistry (Weinheim an der Bergstrasse, Germany) 20201223 7

The first intermolecular early main group metal-alkene complexes were isolated. This was enabled by using highly Lewis acidic Mg centers in the Lewis base-free cations (Me BDI)Mg+ and (tBu BDI)Mg+ with B(C6 F5 )4 - counterions (Me BDI=CH[C(CH3 )N(DIPP)]2 , tBu BDI=CH[C(tBu)N(DIPP)]2 , DIPP=2,6-diisopropylphenyl). Coordination complexes with various mono- ...[more]

PMID: 33197075

Similar Datasets

Project description:The structures and bonding in the heavier group 14 element olefin analogues [E{CH(SiMe3)2}2]2 and [E{N(SiMe3)2}2]2 (E = Ge, Sn, or Pb) and their dissociation into :E{CH(SiMe3)2}2 and :E{N(SiMe3)2}2 monomers were studied computationally using hybrid density functional theory (DFT) at the B3PW91 with basis set superposition error and zero point energy corrections. The structures were reoptimized with the dispersion-corrected B3PW91-D3 method to yield dispersion force effects. The calculations generally reproduced the experimental structural data for the tetraalkyls with a few angular exceptions. For the alkyls, without the dispersion corrections, dissociation energies of -2.3 (Ge), +2.1 (Sn), and -0.6 (Pb) kcal mol-1 were calculated, indicating that the dimeric E-E bonded structure is favored only for tin. However, when dispersion force effects are included, much higher dissociation energies of 28.7 (Ge), 26.3 (Sn), and 15.2 (Pb) kcal mol-1 were calculated, indicating that all three E-E bonded dimers are favored. Calculated thermodynamic data at 25 °C and 1 atm for the dissociation of the alkyls yield ?G values of 9.4 (Ge), 7.1 (Sn), and -1.7 (Pb) kcal mol-1, indicating that the dimers of Ge and Sn, but not Pb, are favored. These results are in harmony with experimental data. The dissociation energies for the putative isoelectronic tetraamido-substituted dimers [E{N(SiMe3)2}2]2 without dispersion correction are -7.0 (Ge), -7.4 (Sn), and -4.8 (Pb) kcal mol-1, showing that the monomers are favored in all cases. Inclusion of the dispersion correction yields the values 3.6 (Ge), 11.7 (Sn), and 11.8 (Pb) kcal mol-1, showing that dimerization is favored but less strongly so than in the alkyls. The calculated thermodynamic data for the amido germanium, tin, and lead dissociation yield ?G values of -12.2, -3.7, and -3.6 kcal mol-1 at 25 °C and 1 atm, consistent with the observation of monomeric structures. Overall, these data indicate that, in these sterically-encumbered molecules, dispersion force attraction between the ligands is of greater importance than group 14 element-element bonding, and is mainly responsible for the dimerization of the metallanediyls species to give the dimetallenes. In addition, calculations on the non-dissociating distannene [Sn{SiMe t Bu2}2]2 show that the attractive dispersion forces are key to its stability.

Project description:Newer systemic therapies have the potential to decrease morbidity and mortality from metastatic colorectal cancer, yet such therapies are costly and have side effects. Little is known about their non-evidence-based use.We conducted a retrospective cohort study using commercial insurance claims from UnitedHealthcare, and identified incident cases of metastatic colon cancer (mCC) from July 2007 through April 2010. We evaluated the use of three regimens with recommendations against their use in the National Comprehensive Cancer Center Network Guidelines, a commonly used standard of care: 1) bevacizumab beyond progression; 2) single agent capecitabine as a salvage therapy after failure on a fluoropyridimidine-containing regimen; 3) panitumumab or cetuximab after progression on a prior epidermal growth factor receptor antibody. We performed sensitivity analyses of key assumptions regarding cohort selection. Costs from a payer perspective were estimated using the average sales price for the entire duration and based on the number of claims.A total of 7642 patients with incident colon cancer were identified, of which 1041 (14%) had mCC. Of those, 139 (13%) potentially received at least one of the three unsupported off-label (UOL) therapies; capecitabine was administered to 121 patients and 49 (40%) likely received it outside of clinical guidelines, at an estimated cost of $718,000 for 218 claims. Thirty-eight patients received panitumumab and six patients (16%) received it after being on cetuximab at least two months, at an estimated cost of $69,500 for 19 claims. Bevacizumab was administered to 884 patients. Of those, 90 (10%) patients received it outside of clinical guidelines, at an estimated costs of $1.34 million for 636 claims.In a large privately insured mCC cohort, a substantial number of patients potentially received UOL treatment. The economic costs and treatment toxicities of these therapies warrant increased efforts to stem their use in settings lacking sufficient scientific evidence.

Dataset Information

Unsupported Mg-Alkene Bonding.

Publications

Unsupported Mg-Alkene Bonding.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure