Add time:09/28/2019         Source:infona.pl

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)4Re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)4Re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)4Re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.

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