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.

In search of a tetradentate thioether thiolate ligand that is more stable toward reductive C–S bond cleavage than the parent ligand ′S4′‐H2 [′S4′‐H2 = 1,2‐bis(2‐mercaptophenylthio)ethane], the novel tris‐phenylene ligand ′tpS4′‐H2 (3) [′tpS4′‐H2 = 1,2‐bis(2‐mercaptophenylthio)phenylene] was synthesized via the nitro and amine compounds ′tpS2(NO2)2′ (1) and ′tpS2(NH2)2′ (2). The coordination of ′tpS4′2– to ruthenium centers resulted in the formation of six‐coordinate [Ru(L)(PR3)(′tpS4′)] complexes (R = Et, L = PEt34; R = Ph, L = PPh35, CO 6, DMSO 7). The X‐ray structure analyses of 4 and 6 revealed that the thiolate donors occupy trans positions; consequently the ′tpS4′2– ligand coordinates in the same way as the ′S4′2– ligand. The stability of the ′tpS4′2– ligand toward reductive C–S cleavage reactions was shown by the synthesis of [Os(PEt3)2(′tpS4′)] (8). In contrast to [Os(PEt3)2(′S4′)], 8 is stable for unlimited periods of time. The X‐ray structure analysis of [Ru(Cl)2(PPh3)(′tpS2(NH2)2′)] (9) demonstrates that the potentially tetradentate ligand ′tpS2(NH2)2′ coordinates in 9 through three donors leaving one NH2 donor dangling.

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