Coordination of CO, NO, N2H2, and Other Nitrogenase Relevant Small Molecules to Sulfur-Rich Ruthenium Complexes with the New Ligand ‘tpS4’2– = 1,2-Bis(2-mercaptophenylthio)phenylene(2–)

Abstract

In the search for ruthenium complexes with sulfur‐dominated coordination spheres that bind, activate, or stabilize nitrogenase relevant molecules, complexes containing the new and robust tetradentate ligand ‘tpS4’–H2 were synthesized. Treatment of [RuCl2(PPh3)3] with ‘tpS4’2– gives [Ru(PPh3)2(‘tpS4’)] (1), which contains two labile PPh3 ligands. The reaction of 1 with PEt3 or DMSO led to substitution of both PPh3 ligands, yielding [Ru(PEt3)2(‘tpS4’)] (2) and [Ru(DMSO)2(‘tpS4’)] (3), respectively. When treated with nitrogenous ligands, complex 1 lost only one PPh3 ligand to yield [Ru(L)(PPh3)(‘tpS4’)] complexes where L = py (7), NH3 (8), N2H4 (9), NH2NHMe (10), and CH3CN (12), all of which are labile. The labile acetonitrile complex [Ru(CH3CN)(PPh3)(‘tpS4’)] (12) proved to be particularly suited as a precursor for the syntheses of other [Ru(L)(PPh3)(‘tpS4’)] complexes. The 18 and 19 valence electron NO complexes [Ru(NO)(PPh3)(‘tpS4’)]BF4 (13) and [Ru(NO)(PPh3)(‘tpS4’)] (14), (NEt4)[Ru(N3)(PPh3)(‘tpS4’)] (15), [Ru(I)(PPh3)(‘tpS4’)] (16), and [Ru(N3)(PPh3)(‘tpS4’)] (17) were obtained starting from complex 12. The labile mononuclear hydrazine complex [Ru(N2H4)(PPh3)(‘tpS4’)] (9) gave the dinuclear complex [μ‐N2H4{Ru(PPh3)(‘tpS4’)}2] (18) by dissociation of hydrazine. The dinuclear diazene complex [μ‐N2H2{Ru(PPh3)(‘tpS4’)}2] (19) was obtained by oxidation of 9 and more readily from [Ru(CH3CN)(PPh3)(‘tpS4’)] (12) and N2H2, which was generated in situ from K2N2(CO2)2 and acetic acid. The molecular structures of 7, 13, 16, 18, and 19 were determined by X‐ray structure analyses. The complexes 18 and 19 represent the first complexes containing the hydrazine/diazene couple, which enables us to compare both the bonding features and the formation of N–H···S bridges when hydrazine and diazene bind to transition metal sulfur sites.

Tris(pyrazolyl)borate Copper Hydroxide Complexes Featuring Tunable Intramolecular H-Bonding

“…The synthetic accessibility and tunability of these py Tp ligands suggest that they may enable H-bonding interactions with other functionalities bridged between two TpM centers. One such target is diazene, an important intermediate in dinitrogen reduction , that is foreshadowed by the isolation of [ iPr2 TpCu] 2 (μ-N 2 H 2 ) …”

Metal–Sulfur Compounds in N2 Reduction and Nitrogenase-Related Chemistry

“…20). 302,334 Monomeric Ru species [Ru(PPh 3 )(L)] (L = "S 4 ", " bu S 4 ", or "tpS 4 ") were reported to bind hydrazine to give [Ru(PPh 3 )-(L)(N 2 H 4 )]. 333,334,337 These complexes were stable enough to be isolated but were not crystallographically identified, perhaps due to the lability of the hydrazine ligand.…”

Uncovering Redox Non-innocent Hydrogen-Bonding in Cu(I)-Diazene Complexes

“…Known transition metal diazene complexes reveal a range of N 2 H 2 coordination motifs (Figure ). − Since the lifetime of free diazene is so short in solution (aqueous N 2 H 2 decay: k = 2.2 × 10 4 M –1 s –1 at 25 °C), isolable metal-diazene complexes enable the study of N 2 H 2 and the effects of coordination at metal centers by a wide variety of spectroscopic and other direct methods. − …”

“…Recent exploration of dynamic secondary coordination sphere Lewis acid and H-bonding interactions include metal-N 2 (Figure a) − and metal-N 2 H 4 (Figure c) complexes that accent studies by Sellmann and co-workers which outline secondary coordination sphere H-bonding with N 2 H 2 ligands (Figure b). − Guided by a developing understanding of the nitrogenase FeMo-cofactor, Sellmann’s complexes modeled possible cluster sulfur–N 2 H 2 H-bonding interactions . These complexes, typically hosting Ru or Fe centers, possess “bifurcated” H-bonding whereby the N 2 H 2 ligand simultaneously engages in a short and long H-bonding interaction with proximal S-donors (Figure b).…”