Transition Metal Complexes with Sulfur Ligands. 136.¹ Enforced Trans Coordination of Thiolate Donors in Electron Rich Iron, Ruthenium, and Nickel [M(L)(pyN₂H₂S₂)] and [M(L)(pyS₄)] Complexes (L = CO, PPh₃, DMSO) (pyN₂H₂S₂^2- = 2,6-Bis(2-mercaptophenylamino)dimethylpyridine(2−); pyS₄^2- = 2,6-Bis(2-mercaptophenylthio)dimethylpyridine(2−))

Abstract

In the course of a systematic study of transition metal complexes exhibiting three properties, electron rich metal centers, core structures with trans thiolate donors, and the capability to bind nitrogenase related small molecules, the pentadentate ligands pyN 2 H 2 S 2 -H 2 ()2,6-bis(2-mercaptophenylamino)dimethylpyridine) and pyS 4 -H 2 ()2,6-bis(2-mercaptophenylthio)dimethylpyridine) have been synthesized. Alkylation of 2(3H)-benzothiazolone by 2,6-bis[(tosyloxy)methyl]pyridine and subsequent alkaline hydrolysis yielded pyN 2 H 2 S 2 -H 2 (3). Template alkylation of [Ni(S 2 C 6 H 4 ) 2 ] 2-(6) by 2,6-bis[(tosyloxy)methyl]pyridine gave [Ni(pyS 4 )] 2 (7) whose acidic hydrolysis yielded pyS 4 -H 2 ‚HCl (9). The reaction of Fe(II) salts with pyN 2 H 2 S 2 2-gave [Fe(pyN 2 H 2 S 2 )] (10). Five-coordinate 10 is paramagnetic (µ eff (293 K) ) 5.34 µ B ), has a trigonal bipyramidal structure, and coordinates CO to give diamagnetic [Fe(CO)(pyN 2 H 2 S 2 )] (11). Although the ν(CO) of 11 (1928 cm -1 (KBr)) indicates electron rich Fe centers and strong Fe-CO bonds, 11 readily dissociated CO in solution. Reactions of pyN 2 H 2 S 2 2-with ruthenium precursor complexes yielded diamagnetic [Ru(L)(pyN 2 H 2 S 2 )], (L ) DMSO (12), PPh 3 (13), or CO (14)) which have practically substitution inert Ru-L bonds. Only 12 could be converted into 14 under drastic conditions (140 bar CO, 120°C, 12 h, THF). Methylation of the thiolate donors to give [Ru(L)(pyN 2 H 2 S 2 -Me 2 )]I 2 (L ) DMSO (15) and PPh 3 (16)) did not labilize the Ru-L bonds. The reaction of Fe(II) salts with pyS 4 2-in the presence of CO yielded [Fe(CO)(pyS 4 )] (17). Complex 17 has a higher ν(CO) (1955 cm -1 in KBr) than 11 but is stable toward Fe-CO dissociation. The spectroscopic data of all synthesized complexes and X-ray structure analyses of 7, 10, 13, 15, 16, and 17 showed that all six-coordinate [M(L)(pyN 2 H 2 S 2 )] and [M(L)(pyS 4 )] complexes uniformly have C 2 symmetrical core structures and trans thiolate donors, thus differing from analogous complexes of pentadentate N x H x S y 2-ligands (x + y ) 5) whose [MN x S y ] cores exhibit either C S or C 1 symmetry and cis or trans thiolate donors. The ν(CO) frequencies in homologous [Fe(CO)(N x H x S y )] complexes (x + y ) 5) showed that exchange of aromatic thioether S for amine NH donors considerably increases the electron density at the iron centers. A minor influence was observed for the exchange of aliphatic thioether S for NH donors or changes of the [FeN x S y ] core structures.

Novel reactions of homodinuclear Ni2complexes [Ni(RNPyS4)]2with Fe3(CO)12to give heterotrinuclear NiFe2and mononuclear Fe complexes relevant to [NiFe]- and [Fe]-hydrogenases

“…The magnetic moment of 1e was determined by Evans' method 55 to give a µ eff value of 2.84µ B at 290 K. This value is lower than the corresponding value for parent complex 1a (3.28µ B ). 54 Fortunately, the molecular structure of complex 1e was unequivocally confirmed by X-ray crystal diffraction analysis (Fig. 2 and Table 1).…”

“…Among complexes 1a-1e, only 1a was previously reported by Sellmann and co-workers. 54 The elemental analysis indicated that each of 1a-1d contains one molecule of MeOH, but 1e does not contain MeOH, obviously due to its purification by recrystallization from a mixed solvent, CH 2 Cl 2 -hexane. In addition, the mass spectra of 1a-1e showed their molecular ion peaks.…”

“…12,19,20 Guided by the well-elucidated active site structures of [NiFe]-and [Fe]-hydrogenases, synthetic chemists have designed and synthesized many transition-metal complexes as models for the active sites of [NiFe]-hydrogenases and [Fe]-hydrogenase. 20,[43][44][45][46][47][48][49][50][51][52][53] Recently, we launched a study on reactions of Fe 3 (CO) 12 with the [RN Py S 4 ]-type ligand-containing homodinuclear Ni 2 complexes [Ni(RN Py S 4 )] 2 (RN Py S 4 = 2,6-bis-(mercaptophenylthiomethyl)-4-R-pyridine; R = H, 54 MeO, Cl, Br, i-Pr), aimed to prepare a new type of [Ni(RN Py S 4 )] unit-containing [NiFe]-hydrogenase model complexes. This is because such model complexes are expected to be more stable than those [NiS 4 ] unit-containing model complexes 30,33 due to one additional coordination of the pyridine N atoms to their Ni atoms.…”

“…Complex 1e possesses C 2 symmetric property and its two Ni-N bond lengths (Ni1-N1 = Ni1A-N1A = 2.087 Å) are very close to those of its parent complex 1a (Ni1-N1 = Ni1A-N1A = 2.060 Å). 54 Synthesis and characterization of heterotrinuclear complexes NiFe 2 (RN Py S 4 )(CO) 5 (2a-2e) and mononuclear complexes Fe(RN Py S 4 )(CO) (3a-3e) Initially, we found that when a suspension of the parent homodinuclear complex [Ni(RN Py S 4 )] 2 (1a, R = H) was treated with Scheme 1 Synthesis of complexes 1a-1e.…”

2,6-Bis(tosyloxymethyl)pyridine

“…For related structures, see: Sellmann et al (1999); Teixidor et al (1999Teixidor et al ( , 2001; Smit et al (2004); Gilbert et al (2000). For the synthesis of the title compound, see: Reger et al (2005).…”