The first homologous series of self-assembled aryl bromo- and aryl cyanocuprates, -argentates, and -aurates; MLi(2)XAr(2) (M = Cu(I), Ag(I), Au(I); X = Br, C(triple bond)N; Ar = [C(6)H(4)CH(2)N(Et)CH(2)CH(2)NEt(2)-2]-).
Reaction of 2 molar equiv of the diamine chelated aryllithium dimers Li(2)(C(6)H(4)[CH(2)N(Et)CH(2)CH(2)NEt(2)]-2)(2) (Li(2)Ar(2)) with the appropriate metal bromide allows the synthesis of the first homologous series of monomeric group 11 bromoate complexes of type MLi(2)BrAr(2) (M = Cu (7), Ag (8), Au (9)). Both in the solid state and in solution, the bromocuprate 7 is isostructural with the bromoargentate 8. The crystal structures of 7 and 8 consist of a MLi(2) core, and each of the two aryl ligands bridges via electron-deficient bonding between the group 11 metal and one Li atom (d(C(ipso)-M) = 1.941(4) (mean) and 2.122(4) (mean) A, for 7 and 8, respectively). The bromine atom exclusively bridges between the two lithium atoms. Each of the ortho-CH(2)N(Et)CH(2)CH(2)NEt(2) moieties is N,N'-chelate bonded to one lithium (d(N-Li) = 2.195(5) and 2.182(0) (mean) A for 7 and 2.154(8) and 2.220(1) (mean) A for 8). Although the MLi(2)BrAr(2) compounds are neutral higher-order -ate species, the structure can also be regarded as consisting of a contact ion pair consisting of two ionic fragments, [Li-Br-Li](+) and [Ar(2)M](-), which are interconnected by both Li-N,N'-chelate bonding and a highly polar C(ipso)-Li interaction. On the basis of NMR and cryoscopic studies, the structural features of the bromoaurate 9 are similar to those of 7 and 8. A multinuclear NMR investigation shows that the bonding between the [Li-Br-Li] and [Ar(2)M] moieties is intermediate between ionic and neutral with an almost equally polarized C(ipso)-Li bond in 7, 8, and 9. Similar reactions between M(C(triple bond)N) and 2 molar equiv of LiAr yield the analogous 2:1 cyanoate complexes of type MLi(2)(C(triple bond)N)Ar(2) (M = Ag (10), Au (11)). Multinuclear NMR studies show that the cyanoate complexes 10 and 11 are isostructural with the bromoate complexes 7, 8, and 9. This paper illustrates that these cyanoaurates may serve as excellent model complexes to gain more insight into the structure of 2:1 cyanocuprates in solution.
Kronenburg
Claudia M P
CM
Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
Jastrzebski
Johann T B H
JT
Boersma
Jaap
J
Lutz
Martin
M
Spek
Anthony L
AL
van Koten
Gerard
G