N ligands / S ligands / Iron / Ruthenium / Pentadentate ligands In order to obtain iron and ruthenium complexes which are [Ru(PPh 3 )(ЈN 3 H 3 S 2 Ј-Me 2 )]I 2 (8) proved as inert towards substitution as 7. Complex 8 could reversibly be analogous to [M(L)(ЈNHS 4 Ј)] and [M(L)(ЈN 2 H 2 S 3 Ј)] complexes [ЈNHS 4 Ј 2-= 2,2Ј-bis(2-mercaptophenylthio)diethylamine(2-), deprotonated to give [Ru(PPh 3 )(ЈN 3 H 2 S 2 Ј-Me 2 )]I (11), in the course of which the [RuPN 3 S 2 ] cores rearrange from C S to ЈN 2 H 2 S 3 Ј 2-= 2,2Ј-bis(2-mercaptophenylamino)diethylsulfide-(2-)] but have electron-richer metal centers, the new C 1 symmetry. Reversible protonation/deprotonation was also found with [Ru(NO)(ЈN 3 H 2 S 2 Ј)] (9) which formed from pentadentate amine thiolate ligand ЈN 3 H 3 S 2 Ј-H 2 [ = 2,2Јbis(2-mercaptophenylamino)diethylamine] (4) was synthe-[RuCl 3 (NO)(PPh 3 ) 2 ] and ЈN 3 H 3 S 2 Ј 2-in the presence of one additional equivalent of LiOMe. Protonation of 9 with HBF 4 sized. The dianion ЈN 3 H 3 S 2 Ј 2-reacted with Fe II salts to give high-spin [Fe(ЈN 3 H 3 10). The NMR spectra and the X-ray structure analysis of 8 proved that the [RuPN 3 S 2 ] cores yielded diamagnetic [Fe(CO)(ЈN 3 H 3 S 2 Ј)] (6) upon reaction with CO. Complex 6 exhibits a low-frequency ν(CO) band of 7 and 8 exhibit a C S -symmetrical meso structure. In all other complexes, however, the [MLN 3 S 2 ] cores exhibit a C 1 -(1934 cm -1 in THF) indicating an electron-rich Fe center and a strong Fe-CO bond. In spite of this, 6 readily dissociated symmetrical structure. It results from the fac-mer coordination mode of the ЈN 3 H 3 S 2 Ј 2-ligand and favors the in solution to 5 and CO. The reaction of [RuCl 2 (PPh 3 ) 3 ] with 7), which proved planarization of amide donors when NH functions are reversibly deprotonated. inert with respect to PPh 3 substitution but could be methylated at the thiolate donors. The resulting StructureϪfunction relationships of transition metal more labile than [Fe(CO)(ЈNHS 4 Ј)], and neither N 2 nor N 2 H 2 , N 2 H 4 , or NH 3 complexes could be obtained with the complexes are primarily determined by the metal oxidation state, type and number of the donor atoms, and the struc-[Fe(ЈN 2 H 2 S 3 Ј)] fragment. Beyond that all [Fe(L)(ЈN 2 H 2 S 3 Ј)]
and corresponding [Ru(L)(ЈN 2 H 2 S 3 Ј)] complexes were ture of the metal ligand core. [1] In quest of metal complexes that combine structural (metal sulfur sites) and functional shown to exhibit the core structure C having thiolate donor atoms in cis positions. The core structure C distinctly differs (reactivity) features of nitrogenase centers, our interest focusses on complexes with multidentate ligands which con-from the [Fe(ЈNHS 4 Ј)] core structure B having trans-thiolate donors. trans-Thiolate donors, however, proved to be essen-tain amine N, thioether S, and thiolate S donors. In this search the [Fe(ЈNHS 4 Ј)] fragment (Scheme 1) was found to tial for the stabilization of molecules such as N 2 H 2 in [µ-N 2 H 2 {Fe(ЈNHS 4 Ј)} 2 ], because only a trans coordination of exist in the diastereomeric forms A and B and to bind N 2 H 2 , N 2 H 4 , NH 3 , and CO, but not N 2 . [2] As high electron thiolate donors allows the formation of strong NϪH•••(S) 2 bridges. [2a,2c] densities at the metal centers usually favor the coordination of N 2 , [3] we tried to increase the iron electron density in the In the series of systematically varied ligands, our next target ligand was ЈN 3 H 3 S 2 Ј-H 2 . It is comparable with the [Fe(ЈNHS 4 Ј)] cores through a systematic substitution of σ-donorϪπ-acceptor thioether functions by σ-donor amine ЈNHS 4 Ј 2Ϫ ligand in so far as all thioether donors are exchanged for amine donors. Simultaneously, the terminal thi-functions.
The first target ligand ЈN 2 H 2 S 3 Ј-H 2 [4] yielded the CO olate donors are maintained in a coordination mode that enables them to occupy, at least in principle, trans positions complex [Fe(CO)(ЈN 2 H 2 S 3 Ј)], whose ν(CO) frequency of 1932 cm Ϫ1 indicated a higher Fe electron density when in six-coordinate metal complexes. compared with to that of [Fe(CO)(ЈNHS 4 Ј)] (1960 cm Ϫ1 ).
However, despite the low-frequency ν(CO) indicating strong Results
FeϪCO π-back-bonding, [Fe(CO)(ЈN 2 H 2 S 3 Ј)] proved much