Rhenium–Germanium Triple Bonds: Syntheses and Reactions of the Germylidyne Complexes mer‐[X₂(PMe₃)₃ReGeR] (X=Cl, I, H; R=m‐terphenyl)

Abstract

A general approach to the first compounds that contain rhenium-germanium triple and double bonds is reported. Heating [ReCl(PMe3)5] (1) with the arylgermanium(II) chloride GeCl(C6H3-2,6-Trip2) (2; Trip=2,4,6-triisopropylphenyl) results in the germylidyne complex mer-[Cl2 (PMe3)3Re≡Ge-C6H3-2,6-Trip2] (4) upon PMe3 elimination. An equilibrium that is dependent on the PMe3 concentration exists between complexes 1 and 4. Removal of the volatile PMe3 shifts the equilibrium towards complex 4, whereas treatment of 4 with an excess of PMe3 gives a 1:1 mixture of 1 and the PMe3 adduct of 2, GeCl(C6H3-2,6-Trip2)(PMe3) (2-PMe3). Adduct 2-PMe3 can be selectively obtained by addition of PMe3 to chlorogermylidene 2. The NMR spectroscopic data for 2-PMe3 indicate an equilibrium between 2-PMe3 and its dissociation products, 2 and PMe3 , which is shifted far towards the adduct site at ambient temperature. NMR spectroscopic monitoring of the reaction of complex 1 with 2 and the reaction of complex 4 with PMe3 revealed the formation of two key intermediates, which were identified to be the chlorogermylidene complexes cis/trans-[Cl(PMe3)4 Re=Ge(Cl)C6H3-2,6-Trip2] (cis/trans-3) by using NMR spectroscopy. Labile chlorogermylidene complexes cis/trans-3 can be also generated from trans-[Cl(PMe3)4 Re≡Ge-C6H3-2,6-Trip2]BPh4 (9) and (nBu4N)Cl at low temperature, and decompose at ambient temperature to give a mixture of complexes 1 and 4. Complex 4 reacts with LiI to give the diiodido derivative mer-[I2(PMe3)3Re≡Ge-C6H3-2,6-Trip2] (5), which undergoes a metathetical iodide/hydride exchange with Na(BEt3H) to give the dihydrido germylidyne complex mer-[H2(PMe3)3Re≡Ge-C6H3-2,6-Trip2] (6). Carbonylation of 4 induces a chloride migration from rhenium to the germanium atom to afford the chlorogermylidene complex mer-[Cl(CO)(PMe3)3Re=Ge(Cl)C6H3-2,6-Trip2] (7). Similarly, MeNC converts complex 4 into the methylisocyanide analogue mer-[Cl(MeNC)(PMe3)3Re=Ge(Cl)C6H3-2,6-Trip2] (8). Chloride abstraction from 4 by NaBPh4 in the presence of PMe3 gives the cationic germylidyne complex trans-[Cl(PMe3)4 Re≡Ge-C6H3-2,6-Trip2]BPh4 (9). Heating complex 4 with cis-[Mo(PMe3)4(N2)2] induces a germylidyne ligand transfer from rhenium to molybdenum to afford the germylidyne complex trans-[Cl(PMe3)4Mo≡Ge-C6H3-2,6-Trip2] (10). All new compounds were fully characterized and their molecular structures studied by X-ray crystallography, which led to the first experimentally determined Re-Ge triple- and double-bond lengths.

Synthesis and Hydrogenation of Heavy Homologues of Rhodium Carbynes: [(Me3P)2(Ph3P)Rh≡E‐Ar*] (E=Sn, Pb)

“…reported a variety of compounds exhibiting a triple bond between a transition metal (M=Nb, Cr, Mo, W, Mn, Re, Fe, Ni, Pt) and a heavy element of the Group 14 (E=Si, Ge, Sn, Pb) [3] . Three synthetic strategies for the synthesis of these carbyne homologues were reported: nucleophilic substitution at organotetrel halides by nucleophilic transition metal complexes; [1, 2, 3c,i] elimination of N 2 /PMe 3 ligands and oxidative addition of organotetrel halides at transition metal complexes [3f,g,k–q] and formation of haloylidene complexes followed by halide abstraction [3d,e] . Hashimoto, Tobita and co‐workers have synthesized tungsten germylyne and tungsten silylyne complexes by dehydrogenation using mesityl isocyanate, nitriles or stepwise proton and hydride abstraction with the hydrido hydrogermylene and hydrido hydrosilylene as starting materials [4] .…”

Synthese und Hydrierung schwerer Homologe eines Rhodium‐Carbins: [(Me3P)2(Ph3P)Rh≡E‐Ar*] (E=Sn, Pb)

“…berichteten über eine Vielzahl von Verbindungen, die eine Dreifachbindung zwischen einem Übergangsmetall (M=Nb, Cr, Mo, W, Mn, Re, Fe, Ni, Pt) und einem schweren Element der Gruppe 14 (E=Si, Ge, Sn, Pb) aufweisen [3] . Es lassen sich drei verschiedene Synthesestrategien für diese Carbinhomologe unterscheiden: Nukleophile Substitution an Organotetrelhalogeniden durch nukleophile Übergangsmetallkomplexe; [1, 2, 3c,i] Eliminierung von N 2 /PMe 3 Liganden und oxidative Addition von Organotetrelhalogeniden an Übergangsmetallkomplexen [3f,g,k–q] oder die Bildung von Haloyliden‐Komplexen und anschließende Halogenidabstraktion [3d,e] . Hashimoto, Tobita und Mitarbeiter synthetisierten Wolframgermylin und ‐silylin‐Komplexe durch Dehydrierung mittels Mesitylisocyanat, Nitrilen oder stufenweiser Proton‐ und Hydridabstraktion an den Hydrogermylen‐Hydriden und Hydrosilylen‐Hydriden als Ausgangsmaterialien [4] .…”

Triple Bonds Between Iron and Heavier Group 15 Elements in AFe(CO)3− (A=As, Sb, Bi) Complexes

“…[9] Such compounds are not common with late transition metals,d espite the synthesized manganese-tin and rhenium-germanium triple bonded cation complexes that are isoelectronic with the Group 6counterparts. [16] Furthermore,aSbFe(CO) 3 À complex was generated in the gas phase in aF ourier transform ion cyclotron resonance spectrometer by reacting Sb 2 À with Fe(CO) 5 ,w hich has been postulated to have SbFe triple bonds based on formal 18-electron count. [13] Af errogallyne was synthesized and characterized to involve Ga Fe triple bonds.…”