Transition metal complexes with sulfur ligands, 143 -: 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-)

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 'tpS(4)'-H-2 were synthesized. Treatment of [RuCl2(PPh3)(3)] with 'tpS(4)'(2-) gives [Ru(PPh3)(2)('tpS(4)')] (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)('tpS(4)')] (2) and [Ru(DMS0)2('tpS4')] (3), respectively. When treated with nitrogenous ligands, complex 1 lost only one PPh3 ligand to yield [Ru(L)(PPh3)('tpS(4)')] 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)('tpS(4)')] (12) proved to be particularly suited as a precursor for the syntheses of other [Ru(L) (PPh3)('tpS(4)')] complexes. The 18 and 19 valence electron NO complexes [Ru(NO)(PPh3)( 'tpS(4)')]BF4 (13) and [Ru-(NO)(PPh3)('tpS(4)')] (14), (NEt4)[Ru(N-3)(PPh3) ('tpS(4)')] (15), [Ru(I) (PPh3)('tpS(4)')] (16), and [Ru(N-3)(PPh3) ('tpS(4)')] (17) were obtained starting from complex 12. The labile mononuclear hydrazine complex [Ru(N2H4)(PPh3)('tps(4)')] (9) gave the dinuclear complex [mu-N2H4{Ru(PPh3)('tpS(4)')}(2)] (18) by dissociation of hydrazine. The dinuclear diazene complex [mu-N2H2{Ru(PPh3)('tpS(4)')}(2)] (19) was obtained by oxidation of 9 and more readily from [Ru(CH3CN)(PPh3) ('tpS(4)')] (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.