Dissolution of Alkali Metals in Aromatic Hydrocarbon Solvents by Cryptate Formation

Abstract

The methyl group is connected to the carbyne-carbon by a normal single bond [149(2) pm]. The Cr-C-CH, arrangement appears to be linear, even though F , calculations with disordered bent molecular models show no influence on the R factor provided that the angular deviation does not exceed 5 .(CO)@"CHj)3](Br)CrCCH, (3) crystallizes with two crystallographically independent molecules in the asymmetric unit of the cell. Both independent molecules have identical geometries within experimental error. Mean values of the bond lengths are: Cr-CC-0 193(4), Cr-Br 260.3(5). Cr-P 239.6(9) pm. The Cr-CcarhYne separation [ 168(3) pm] is almost identical with that in (2). The deviation of the Cr-C-CH3 group from linearity is not significant {177(3) 3. Table 2 shows some bond lengths for chromium and tungsten complexes with metal-carbon single bonds, metal-carbene bonds which can be regarded as partial double bonds, and the new metal-carbyne bonds.The metal-carbyne carbon bonds are shorter by cu. 40pm than a metal-carbon single bond in the case of tungsten and by cu. 50pm in the case of chromium. For comparison, the shortening in the series alkane, alkene and alkyne is 33pm (ethane 154. ethylene 134, acetylene 121 pm)["'. The extremely short metal-carbon separation in the compounds of this study supports the proposition of a metal-carbon triple bond.

Synthesis and Characterization of Organolanthanidocene(III) (Ln = La, Ce, Pr, Nd) Complexes Containing the 1,4-Cyclohexa-2,5-dienyl Ligand (Benzene 1,4-Dianion): Structures of [K([18]-crown-6)][Ln{η5-C5H3(SiMe3)2-1,3}2(C6H6)] [Cp‘ ‘ = η5-C5H3(SiMe3)2-1,3; Ln = La, Ce, Nd]

“…The UV−vis spectra in benzene of complexes 5 − 8 showed a similar pattern of absorption bands: at 463 ± 23 nm, a shoulder at 348 ± 10 nm, and a band at 280 ± 2 nm. These values are similar to those reported previously for a solution of potassium and (perhydrodibenzo-18-crown-6) in benzene (λ max 435 and 300 nm), or potassium and DME in benzene at 203 K (λ max 435 and 285 nm), which in both cases were attributed to the benzene monoanion. The IR spectrum of each of 5 − 8 was identical.…”

Structural and Functional Evolution of Metallacrowns

“…Cu II complexation equilibria in MeOH/H 2 O (9:1) solutions with S-phenylalanine and S-tryptophan hydroxamic acid ligands, along with ESI-MS studies, suggest the existence of [Cu 5 L 4 ] 2+ species, besides other species such as [CuL] + , [CuL 2 ], and [CuL 2 ] -. 395 The formation constants are log β ) 51.58(9) and 52.37 (11), respectively. In the ESI-MS spectra, the most abundant species in both cases correspond to [Cu 5 L 4 ] 2+ .…”

“…In 1967 Pederson reported the synthesis of macrocyclic crown ethers and their ability to selectively bind alkali and alkaline earth ions, , and since then supramolecular compounds have captivated chemists. − Following Pederson's revolutionary discovery, a plethora of organic macrocyclic molecules were synthesized including thiacrown ethers, azacrown ethers, lariat ethers, chiral crown ethers, , cryptands, − spherands, , cryptahemispherands, , hemispherands, calixarenes, − cavitands, − hemicarcerands, carcerands (molecular containers), − and boron macrocycles. − These complexes have the ability to bind cations and anions, function as ion transport agents, stabilize unstable molecules, and act as a host for chemical reactions. This work led to the 1987 Nobel Prize in chemistry being awarded to Charles Pederson, Jean-Marie Lehn, and Donald Cram for their pioneering work in the field.…”

Nonclassical Organolanthanoid Metal Chemistry: [K([18]-crown-6)(η2-PhMe)2]X (X = [(LnCpt3)2(μ-H)], [(LnCp‘ ‘2)2(μ-η6:η6-PhMe)]) from [LnCpx3], K, and [18]-crown-6 in Toluene (Ln = La, Ce; Cpt = η5-C5H4SiMe2But; Cp‘ ‘ = η5-C5H3(SiMe3)2-1,3)

“…Hydrolysis of any of 1a , b and 2a , b afforded toluene (GC-MS) and a small amount of H 2 ( 1 H NMR) but no methylcyclohexadiene (cf., cyclohexa-1,4-diene from D 3,4 but not E 5,6 ). Solution EPR spectra of the freshly prepared 1a , b in toluene revealed the characteristic quintet of [PhMe] - . Solid-state EPR spectra showed broad signals for each complex at a g value very close to that of the free electron (2.0023).…”