Franz Geipel

Highly Soluble Sulfur-Rich [Ni(L)(siS3)] Complexes Containing the New Ligand Bis(2-mercapto-3-trimethylsilylphenyl) Sulfide(2−) (siS32−)

The new organosulfur ligands siS3-H2 [siS32− = bis(2-mercapto-3-trimethylsilylphenyl) sulfide(2−)] and caS3-H2 [caS32− = bis(2-mercapto-3-carboxyphenyl) sulfide(2−)] were synthesized from HS3-H2 [HS32− = bis(2-mercaptophenyl) sulfide(2−)], n-butyllithium, and Me3SiCl or CO2/H+. Reaction of siS3-H2 with Ni(ac)2·4H2O gave the air-stable and well-soluble trinuclear complex [Ni(siS3)]3 (1) whose structure was determined by X-ray crystallography. Reactions of complex 1 with nucleophiles L [L = PR3 (R = nPr, Ph, Cy), N2H4, StBu−, and Cl−] yielded the corresponding neutral or anionic complexes, which were isolated as [Ni(PR3)(siS3)] [R = nPr (2), Ph (3), Cy (4)], Bu4N[Ni(Cl)(siS3)] (5), Bu4N[Ni(StBu)(siS3)] (6), and [Ni(N2H4)(siS3)] (8). The azido complex Et4N[Ni(N3)(siS3)] (7) was prepared from Me3SiN3 and the precursor chloro complex Et4N[Ni(Cl)(siS3)]. Reaction of 1 with NH3 yielded labile [Ni(NH3)(siS3)] (9), which was characterized in solution by 1H and 13C NMR spectroscopy. Analogously, 1 reacts with nicotinamide (NA) or diethylnicotinamide (NAEt2) to give, from equilibrium reactions, the corresponding mononuclear [Ni(L)(siS3)] complexes with L = NA, NAEt2. X-ray structure determinations showed that 1, 3, 4, 5, and 7 all exhibit tetrahedrally distorted planar [Ni(L)(siS3)] fragments. Complex 7 is the first structurally characterized azidonickel complex with a coligand having exclusively sulfur donors. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Mononuclear Carbene Dithiolate [Ni(NHX)(′S2C ′)] Complexes with HNX = HNPiPr3 or HNSPh2 Coligands (′S2C ′ 2– = 1,3‐ImidazolidinylN,N′‐bis(2‐benzenethiolate)(2–))

Cleavage reactions of the dinuclear [{Ni(′S2C ′)}2] · DMF (′S2C ′ 2– = 1,3-imidazolidinyl-N,N′-bis(2-benzenethiolate)(2–)) with HNPiPr3 or HNSPh2 yielded the mononuclear complexes [Ni(NHPiPr3)(′S2C ′)] (1) and [Ni(NHSPh2)(′S2C ′)] (2) which have been completely characterized. The nickel-carbene-dithiolate [Ni(′S2C ′)] moiety is one of the very rare complex fragments that are able to coordinate both HNPR3 or HNSR2. IR spectra and X-ray structure determinations show that 1 and 2 exhibit intramolecular N–H…S(thiolate) hydrogen bonds. Geometric parameters and NMR spectroscopic data of 1 and 2 are compatible with N–X single bonds and ylidic structures of the HNPiPr3 and HNSPh2 ligands. Comparison of Ni–N distances in diamagnetic and paramagnetic [Ni(NHSPh2)] complexes was rendered possible through the X-ray structure determination of the homoleptic [Ni(NHSPh2)6]Cl2 (3) which formed as minor by-product in the synthesis of 2.

[Ni(NHPnPr3)‘S’3')], der erste Nickel-Thiolat-Komplex mit Modellcharakter für das Nickel-Cysteinat-Zentrum und die Reaktivität von [NiFe]-Hydrogenasen

Wie aktivieren [NiFe]-Hydrogenasen H2? Hydrogenasen sind Schlusselenzyme im biologischen Wasserstoff- und Energie-Metabolismus, aber der Mechanismus der H2-Aktivierung ist ungeklart. Besonders kontrovers werden die Oxidationsstufen der beteiligten Metalle diskutiert. Der Titelkomplex demonstriert, dass ein verzerrtes diamagnetisches NiII-Zentrum und Thiolat-Donoren ausreichen (siehe Bild), um die Schlusselreaktion von Hydrogenasen, die H2-Heterolyse, zu katalysieren.

Mononuclear Ni, Pd and Pt Complexes with ′S3′2– Thioether Thiolate and HNPnPr3 Phosphorane Imine Ligands [′S3′2– = Bis(2‐mercaptophenyl)sulfide (2–)]

Reaction of the trinuclear [M(′S3′)]3 complexes {M = Ni (4), Pd (5), Pt (6); ′S3′2– = bis(2-mercaptophenyl)sulfide (2–)} with HNPnPr3 yielded the new phosphorane imine complexes [M(NHPnPr3)(′S3′)] {M = Ni (1), Pd (2), Pt (3)}. The complexes 1–3 have been completely characterized and are rare examples of mononuclear phosphorane imine complexes with late transition metals. Spectroscopic and structural results indicate that the HNPnPr3 ligands favor the ylidic structure when binding to [M(′S3′)] fragments. X-ray structure determinations showed that [M(NHPnPr3)(′S3′)] complexes associate through N–H···S(thiolate) bridges to give centrosymmetric dimers.