2013/02/27 by Alexander C. Filippou, Uttam Chakraborty, Gregor Schnakenburg
paper · doi:10.1002/chem.201300017
Abstract A general approach to the first compounds that contain rhenium–germanium triple and double bonds is reported. Heating [ReCl(PMe 3 ) 5 ] ( 1 ) with the arylgermanium(II) chloride GeCl(C 6 H 3 ‐2,6‐Trip 2 ) ( 2 ; Trip=2,4,6‐triisopropylphenyl) results in the germylidyne complex mer ‐[Cl 2 (PMe 3 ) 3 ReGeC 6 H 3 ‐2,6‐Trip 2 ] ( 4 ) upon PMe 3 elimination. An equilibrium that is dependent on the PMe 3 concentration exists between complexes 1 and 4 . Removal of the volatile PMe 3 shifts the equilibrium towards complex 4 , whereas treatment of 4 with an excess of PMe 3 gives a 1:1 mixture of 1 and the PMe 3 adduct of 2 , GeCl(C 6 H 3 ‐2,6‐Trip 2 )(PMe 3 ) ( 2 ‐PMe 3 ). Adduct 2 ‐PMe 3 can be selectively obtained by addition of PMe 3 to chlorogermylidene 2 . The NMR spectroscopic data for 2 ‐PMe 3 indicate an equilibrium between 2 ‐PMe 3 and its dissociation products, 2 and PMe 3 , 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 PMe 3 revealed the formation of two key intermediates, which were identified to be the chlorogermylidene complexes cis / trans ‐[Cl(PMe 3 ) 4 ReGe(Cl)C 6 H 3 ‐2,6‐Trip 2 ] ( cis / trans ‐ 3 ) by using NMR spectroscopy. Labile chlorogermylidene complexes cis / trans ‐ 3 can be also generated from trans ‐[Cl(PMe 3 ) 4 ReGeC 6 H 3 ‐2,6‐Trip 2 ]BPh 4 ( 9 ) and ( n Bu 4 N)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 ‐[I 2 (PMe 3 ) 3 ReGeC 6 H 3 ‐2,6‐Trip 2 ] ( 5 ), which undergoes a metathetical iodide/hydride exchange with Na(BEt 3 H) to give the dihydrido germylidyne complex mer ‐[H 2 (PMe 3 ) 3 ReGeC 6 H 3 ‐2,6‐Trip 2 ] ( 6 ). Carbonylation of 4 induces a chloride migration from rhenium to the germanium atom to afford the chlorogermylidene complex mer ‐[Cl(CO)(PMe 3 ) 3 ReGe(Cl)C 6 H 3 ‐2,6‐Trip 2 ] ( 7 ). Similarly, MeNC converts complex 4 into the methylisocyanide analogue mer ‐[Cl(MeNC)(PMe 3 ) 3 ReGe(Cl)C 6 H 3 ‐2,6‐Trip 2 ] ( 8 ). Chloride abstraction from 4 by NaBPh 4 in the presence of PMe 3 gives the cationic germylidyne complex trans ‐[Cl(PMe 3 ) 4 ReGeC 6 H 3 ‐2,6‐Trip 2 ]BPh 4 ( 9 ). Heating complex 4 with cis ‐[Mo(PMe 3 ) 4 (N 2 ) 2 ] induces a germylidyne ligand transfer from rhenium to molybdenum to afford the germylidyne complex trans ‐[Cl(PMe 3 ) 4 MoGeC 6 H 3 ‐2,6‐Trip 2 ] ( 10 ). All new compounds were fully characterized and their molecular structures studied by X‐ray crystallography, which led to the first experimentally determined ReGe triple‐ and double‐bond lengths.