Zur Wechselwirkung von 2,2′‐Dihydroxydiphenyl und Brenzcatechin mit 3d‐Übergangsmetallhalogeniden

Abstract

2,2′‐Diphenylendioxydilithium reagiert mit wasserfreiem MnCl2, CoCl2, NiCl2 und CuCl2 unter Bildung der entsprechenden Metallkomplexe. Eine andere Möglichkeit zur Darstellung solcher Komplexe ist die Umsetzung von 2,2′‐Dihydroxydiphenyl mit Metallchloriden in Gegenwart von Aminen als HCl‐Akzeptoren. Durch Wechselwirkung mit Aminen und Triphenylphosphin sind tetra‐ bzw. hexakoordinierte Amin‐ bzw. Phosphinkomplexe zugänglich. Bei der Reaktion von 2,2′‐Diphenylendioxydilithium mit Metallpyridinithicyanaten werden die Pyridinkomplexe erhalten. Brenzcatechin reagiert mit den Metallchloriden bei Gegenwart eines Überschusses an Triethylamin zu den entsprechenden Aminkomplexen.

Axially asymmetric metal alkyls. Part 1. Lithium alkyls of 2,2′-dimethylbiphenyl and its trimethylsilylmethylated compounds: crystal structures of [{Li(Me2NCH2CH2NMe2)}2{(2-CHRC6H4)2}] for R = H (polymeric) and R = SiMe3(monomeric)

“…This phenomenon is similar to the analogous para protons of lithio-o-xylene species." No 13C-'Li coupling was detected for (7), (9), and ( 14), a common occurrence for organolithium compounds, which has been attributed to a combination of bond exchange, likely in the 'contact ionpair ' structures ( 9) and ( 12), and 'Li quadrupole r e l a x a t i ~n . ~~ Other n.m.r.…”

“…Furthermore, the ability to prepare (9) clearly demonstrates the origin of restricted metallation is not a steric effect; a conceivable cause comes from consideration of the X-ray structure results of (7) and (9) (see structural commentary). Metal-alkyl interactions in (7) are of the three-centre two-electron type, as found in bis( bicyclo[ 9) is best described as a ' contact ion-pair ' type exemplified by the bonding in [{Li(tmen))(CPh3)]. '9 In the structure of (9) extensive delocalisation of charge is assumed.…”

“…With -CH2SiMe3 rather than -CH3 on the adjacent ring the anticipated increase in -CH2SiMe3 acidity may effectively compensate this effect. In the case of ( 6) if the monolithio-species bonding is similar to that in (7) the nature of the lithium-alkyl interaction would allow little prospect for charge delocalisation and thus lowering of the acidity of the residual -CH3 group.…”

“…The Grignard reagent was prepared in modest yields (60%), whereas attempted synthesis using the bromo-compound (1 1) typically gave a low yield (20%). The use of chloride rather than bromide to limit the competing coupling reactions is well known even for simple Grignard reagents 26 and for benzylic Grignards is highlighted by the critical conditions of concentration, temperature, and solvent required for high-yield di-Grignard reagents of a,a'-dichloroo-xylene and 2,2'-bi~(chloromethyI)biphenyl.~ Structural Commentary.-Compound (7). The structure determination confirms the assignment of stoicheiometry as [(Li(tmen)}2{(2-CH2C6H4)2)]; one formula unit comprises the asymmetric unit of the structure, the nature of which is an infinite polymer generated by the 4, screw axis of the space group along c (Figure 1).…”

“…Regrettably, the imprecision of the structure determination does not permit the experimental location of the associated hydrogen atoms; by implication from the above, the co-ordination about each methylene carbon may be trigonal bipyramidal. In compound (7), the lithium atoms are associated quite distinctly with the methylene carbon only;…”