Aryl Oligogermanes as Ligands for Transition Metal Complexes

Abstract

The ligand properties of a series of aryl oligogermanes R3Ge‐GeAr3, 3–7 [Me3Ge‐GePh3 (3), Me3Ge‐Ge(pTol)3 (4), Ph3Ge‐GePh3 (5), (C6F5)3Ge‐GePh3 (6), Ph3Ge‐GeMe2GePh3 (7)] for the synthesis of transition metal carbonyl complexes such as R3Ge‐GeAr2(R′C6H4‐η6)M(CO)3 (M = Cr, 3a–7a; M = Mo, 3b; M = W, 3c) were investigated. The target complexes were obtained in moderate yields using several different synthetic approaches. The physicochemical properties of these new derivatives were investigated by IR, UV/Vis, NMR spectroscopy, electrochemistry, and DFT calculations. The molecular structures of 3c, 4a, and 5a were studied by single‐crystal X‐ray diffraction analysis. A comparative analysis of donor and acceptor properties of aryl oligogermanes as ligands for transition metal carbonyl complexes is reported.

Aryl Germanes as Ligands for Transition Polymetallic Complexes: Synthesis, Structure, and Properties

“…The attempts to synthesize the related dimetallic complexes under similar conditions using Ph 3 GeGePh 3 or Ph 3 GeGeMe 2 GePh 3 resulted only in the formation of the corresponding monometallic complexes, Ph 3 GeGePh 2 [(η 6 ‐C 6 H 5 )Cr(CO) 3 ] and Ph 3 GeGeMe 2 GePh 2 [(η 6 ‐C 6 H 5 )Cr(CO) 3 ], that have been described previously . This indicates that the synthesis of dimetallic species strongly depends on the structure of the initial catenated germanium compound.…”

“…On the contrary, for the compounds 4a and 5a ( C 2 v symmetry), one set of signals is observed, indicating a high degree of symmetry within the molecule and a magnetic equivalence of all coordinated phenyl groups. Furthermore, a comparison between the chemical shifts observed for 3 with those observed for 3a indicates that the non‐coordinated Ph group displays more deshielded 1 H and 13 C NMR signals, which is indicative of a high degree of conjugation between all parts of a molecule (σ‐ and π‐), and of an electron donation to the Cr(CO) 3 moiety.…”

“…The classical method to prepare Cr carbonyl complexes requires to reflux Cr(CO) 6 ( 1 ) at high temperature (in decalin, tetralin, di‐ n ‐butyl ether or other high‐boiling solvents), in the presence of an excess of the desired arene. The reaction is usually sluggish and requires to be heated up for a long period of time during which the product might decompose due to its thermal instability.…”

“…Also, when more reactive Cr sources were used, such as an excess of Cr(CO) 3 (NCMe) 3 in THF (up to 3.0 eq. ), in presence of Ph 3 GeGeMe 3 ( 3 ) or Ph 3 GeGeMe 2 GePh 3 , only the corresponding mono chromium products, RMe 2 GeGePh 2 [(η 6 ‐C 6 H 5 )Cr(CO) 3 ] (R= Me or GePh 3 , respectively) were obtained …”

“…Therefore studies of the fundamental properties of catenated molecular compounds will have a significant impact on their use for new applications. It has been shown previously that the introduction of a single transition metal fragment into a catenated molecule significantly changes its properties Therefore, the introduction of a Cr(CO) 3 group, a strong electron acceptor, within the framework of an aryl catenated Ge compound should have a significant impact on the physical and chemical properties of the compound . Besides, arene chromium carbonyl complexes have found to have wide applications in synthesis, catalysis, medicine, and material chemistry.…”