Tuning the potential of redox-active diphosphine ligands based on the alkyne complexes [Tp*W(CO)L{η-C(PPh)}].

Eleven complexes with the general formula [Tp*W(CO)L{η-C(PPh)}] {Tp* = hydridotris(3,4,5-trimethylpyrazolyl)-borate, L = F, Cl, Br, I, MeS, PhS, pyCHS, CN and TfO; = 0 and L = CHCN and pyridine; = 1} have been synthesized and fully characterized. Depending on L, the oxidation process from W(II) to W(III) is detected between -0.28 and +0.

Synthesis and coordination behaviour of 1-1,2,3-triazole-4,5-dithiolates.

The preparative access to and first group 10 metal complexes of novel 1-1,2,3-triazole-4,5-dithiolate ligands (tazdt) are reported. A set of S-protected 1-1,2,3-triazole-4,5-dithiol derivatives with R = 2,6-dimethylphenyl (Xy) or benzyl (Bn) at N1 and with R = Bn or trimethylsilylethyl (TMS-ethyl) at both S atoms were synthesized by a 1,3-dipolar cycloaddition catalysed by either Ru(II) or Cu(I). Extensive investigations on the removal of the protective groups resulted the reductive removal of benzyl groups to be superior in isolating the free 4,5-dithiols of RNC(SH) with R = Xy (H-8) or Bn (H-9).

Migratory insertion of isocyanide into a ketenyl-tungsten bond as key step in cyclization reactions.

Treatment of the side-on tungsten alkyne complex of ethinylethyl ether [Tp*W(CO)(η-,'-HCCOCHCH)] {Tp* = hydridotris(3,4,5-trimethylpyrazolyl)borate} (2a) with -BuNI afforded the end-on ketenyl complex [Tp*W(CO)(κ-HCCO)] (4a). This formal 16 ve complex bearing the prototype of a ketenyl ligand is surprisingly stable and converts only under activation by UV light or heat to form a dinuclear complex [Tp*W(CO)(μ-CCH)] (6). The ketenyl ligand in complex 4a underwent a metal template controlled cyclization reaction upon addition of isocyanides.

Development and application of redox-active cyclometallating ligands based on W(II) alkyne complexes.

The assembly of dinuclear complexes with the ultimate smallest ditopic ligands based on complexes of methyl substituted alkynes is presented. In fact, the coordination of Ru(II) and Ir(III) by a W alkyne complex based cyclometallating metalla-ligand causes close intermetallic electronic cooperation, which substantially changes the electrochemical and photophysical properties of the single isolated moieties.

Metal/Metal Redox Isomerism Governed by Configuration.

A pair of diastereomeric dinuclear complexes, [Tp'(CO)BrW{μ-η -C,C'-κ -S,P-C (PPh )S}Ru(η -C H )(PPh )], in which W and Ru are bridged by a phosphinyl(thiolato)alkyne in a side-on carbon P,S-chelate coordination mode, were synthesized, separated and fully characterized. Even though the isomers are similar in their spectroscopic properties and redox potentials, the like-isomer is oxidized at W while the unlike-isomer is oxidized at Ru, which is proven by IR, NIR and EPR-spectroscopy supported by spectro-electrochemistry and computational methods. The second oxidation of the complexes was shown to take place at the metal left unaffected in the first redox step.

Facile Synthesis of a Stable Side-on Phosphinyne Complex by Redox Driven Intramolecular Cyclisation.

Alkyne complexes with vicinal substitution by a Lewis acid and a Lewis base at the coordinated alkyne are prospective frustrated Lewis pairs exhibiting a particular mutual distance and, hence, a specific activation potential. In this contribution, investigations on the generation of a W alkyne complex bearing a phosphine as Lewis base and a carbenium group as Lewis acid are presented. Independently on potential substrates added, an intramolecular cyclisation product was always isolated.

Pathways to Polynuclear Complexes with α-,-Substituted Alkynes as Bridging Ligands.

Recently, alkyne complexes with terminal thiolate/amide substitution have been shown to act as ,-chelate ligands in dinuclear complexes. In this study, the detailed synthesis and reactivity of W(II) alkyne complexes bearing different amino groups in the α-position are reported. The preparative scheme starts with cationic alkyne complexes [Tp'W(CO)-η-,'-CBr(SR)]PF {Tp' = hydridotris(3,5-dimethylpyrazolyl)borate, R = benzyl (Bn), CHSiMe}, which are obtained by applying free bromo alkynes.

Ultrafast Energy Transfer in Dinuclear Complexes with Bridging 1,10-Phenanthroline-5,6-Dithiolate.

We report herein the preparation and characterization of dinuclear complexes with the bridging ligand 1,10-phenanthroline-5,6-dithiolate (phendt) bearing Ru(bpy) or Ir(ppy) at the diimine moiety and Ni(dppe), Ni(dppf), CoCp, RhCp*, and Ru( p-Me-Pr-benzene) at the dithiolate unit. In comparison with the mononuclear precursors used in the synthesis, all dinuclear complexes were characterized by absorption and photoluminescence spectroscopy as well as cyclic voltammetry. Because of the beneficial spectral and electrochemical properties of the Ir/Co complex for a light-driven charge separation, this complex was investigated in detail by time-resolved luminescence {nanosecond (ns)-resolution} and transient absorption spectroscopy {femtosecond (fs)-resolution}.

Sterically encumbered metalla-diphosphines: unlocking alkyne rotation by Pt coordination.

We present the synthesis and coordination chemistry of a series of W alkyne complexes with symmetric and asymmetric acetylene diphosphines. Chelate-like P,P'-coordination of PtCl cause a drastic potential change of the W centered oxidation proving intermetallic cooperativity. The choice of peripheric P-substituents has a measurable influence on the potential itself as well on the respective potential change upon coordination.

Synthesis and activation potential of an open shell diphosphine.

A paramagnetic W alkyne complex bearing free terminal diphenylphosphino groups at the side-on coordinated alkyne was synthesized using a stepwise template strategy. This moderately stable metal supported open shell diphosphine shows an unprecedented spontaneous splitting of nitric oxide providing a W-η-C{P(NH)Ph}{P(O)Ph} complex featuring an amino phosphonium and a phosphine oxide substituent.

Minimalistic Ditopic Ligands: An α-S,N-Donor-Substituted Alkyne as Effective Intermetallic Conjugation Linker.

The capability of donor-substituted alkynes to link different metal ions in a side-on carbon donor-chelate coordination mode is extended from the donor centers S and P to the second period element N. The complex [Tp'W(CO)2 {η(2) -C2 (S)(NHBn)}] (Tp'=hydrido-tris(3,5-dimethylpyrazolyl)borate, Bn=benzyl) bearing a terminal sulfur atom and a secondary amine substituent is accessible by a metal-template synthesis. Subsequent deprotonation allowed the formation of remarkably stable heterobimetallic complexes with the [(η(5) -C5 H5 )Ru(PPh3 )] and the [Ir(ppy)2 ] moiety.

Dual nucleophilic substitution at a W(ii) η(2)-coordinated diiodo acetylene leading to an amidinium carbyne complex.

The synthesis and reactivity of a W(ii) C2I2 complex towards various nucleophiles are described. Soft, aprotic nucleophiles like 4-dimethylaminopyridine (DMAP) lead to substitution of one CO at tungsten, whereas reaction with an excess of benzylamine results in a dual nucleophilic substitution at the alkyne moiety involving the rearrangement to a novel cationic amidinium carbyne complex.

Understanding the Excited State Behavior of Cyclometalated Bis(tridentate)ruthenium(II) Complexes: A Combined Experimental and Theoretical Study.

The synthesis and characterization of the donor-acceptor substituted cyclometalated ruthenium(II) polypyridine complex isomers [Ru(dpb-NHCOMe)(tpy-COOEt)](PF6) 1(PF6) and [Ru(dpb-COOEt)(tpy-NHCOMe)](PF6) 2(PF6) (dpbH = 1,3-dipyridin-2-ylbenzene, tpy = 2,2';6,2"-terpyridine) with inverted functional group pattern are described. A combination of resonance Raman spectroscopic and computational techniques shows that all intense visible range absorption bands arise from mixed Ru → tpy/Ru → dpb metal-to-ligand charge transfer (MLCT) excitations. 2(PF6) is weakly phosphorescent at room temperature in fluid solution and strongly emissive at 77 K in solid butyronitrile matrix, which is typical for ruthenium(II) polypyridine complexes.

A new class of azadipnictiridines generated by an unusual rearrangement reaction.

Dipnictadiazanediyls, [E(μ-NR)]2 (E = P, As), the pnictogen analogues of cyclobutandiyl, were found to react readily with alkynes forming [2.1.1]bicyclic structures.

Dinuclear Ru/Ni, Ir/Ni, and Ir/Pt complexes with bridging phenanthroline-5,6-dithiolate: synthesis, structure, and electrochemical and photophysical behavior.

We report the synthesis and full characterization of dinuclear complexes with the bridging ligand phenanthroline-5,6-dithiolate (phendt(2-)) featuring the [Ru(bpy)2](2+) or Ir(ppy)2](+) fragment at the diimine donor center and the [Ni(dppe)](2+) or [Pt(phen)](2+) complex moiety at the dithiolate group. The molecular structures of the mononuclear complexes [(C5H5)2Ti(S,S'-phendt)] and [(ppy)2Ir{N,N'-phendt-(C2H4CN)2}](PF6) as well as the dinuclear complex [(C5H5)(PPh3)Ru(phendt)Ni(dppe)](PF6) determined by X-ray diffraction (XRD) studies are compared. Photophysical studies with mononuclear [(bpy)2Ru{phendt-(C2H4CN)2}](2+) and [(ppy)2Ir{phendt-(C2H4CN)2}](+) as well as dinuclear [(bpy)2Ru(phendt)Ni(dppe)](2+) and [(ppy)2Ir(phendt)Ni(dppe)](+) uncovered an effective luminescence quenching in the dinuclear complexes.

Acetylene dithiolate linking up the [Tp'W(CO)(CN)] moiety with Ru(II) or Pd(II.).

A series of heterodinuclear complexes with acetylene dithiolate (acdt(2-) ) as the bridging moiety were synthesised by a facile one-pot procedure that avoided use of the highly elusive acetylene dithiol. Generation of the W-Ru complex [Tp'W(CN)(CO)(C2 S2 )Ru(η(5) -C5 H5 )(PPh3 )] (Tp'=hydrotris(3,5-dimethylpyrazolyl)borate) and the W-Pd complexes [Tp'W(CN)(CO)(C2 S2 )Pd(dppe)] and [Tp'W(CO)2 (C2 S2 )Pd(dppe)][PF6 ] (dppe=1,2-bis(diphenylphoshino)ethane), which exhibit a [W(η(2) -κ(2) -C2 S2 )M] core (M=Ru, Pd), was accomplished by using a transition-metal-assisted solvolytical removal of the Me3 Si-ethyl thiol protecting groups. All intermediate species of the reaction have been fully characterised.

Ethenedithione (S=C=C=S): trapping and isomerization in a cobalt complex.

Swing bridge: The triplet species ethenedithione has been generated within the coordination sphere of cobalt, leading to a dinuclear μ-η(2)-η(2)-C(2)S(2) complex (see picture: C gray, Co blue, P purple, S yellow). Depending on the solvent, the C(2)S(2) moiety displays a transoid or a cisoid geometry. This isomerization step changes the sign of the magnetic coupling between the cobalt centers.

Acetylenedithiolate as directional bridging ligand in cobalt(I) alkyne platinum dithiolato bimetallic complexes.

The eta(2)-C,C-acetylenedithiolate (acdt2-) complex K[(triphos)Co(acdt)], K-5, {triphos = 1,1,1-tris(diphenylphosphinomethyl)ethane} was obtained by consecutive removal of S-protection groups in [(triphos)Co(1)]PF6, 3-PF6 (1 = 1-Trimethylsilyl-7-phenyl-3,6-dithiahept-4-ine). Reaction of K-5 with selected Pt(II) salts resulted in the formation of the new heterobimetallic complexes [(phen)Pt(5)]BPh4, 6-BPh4, (phen = 1,10-phenanthroline) and [(dppe)Pt(5)]BPh4, 7-BPh4, {dppe = 1,2-bis(diphenylphosphino)ethane}, which were fully characterized. X-ray diffraction studies showed that Co and Pt are linked by acdt2- in the eta(2)-C,C-2-S,S-bridging mode.

Coordination chemistry of the sulfur analog of tricatechol siderophores.

Reaction of the siderophore analog tris(benzene-o-dithiol) ligand H6-1 with Ti(OPr)4 in methanol leads to the formation of the siderophore analog complex (Ph4As)2[Ti(1)3] exhibiting exclusively thiolato coordination to the metal center.

Chances and limits of the coordination chemistry with bis(benzene-l,2-dithiolato) ligands.

The incorporation of benzene-l,2-dithiolato building blocks into supramolecular coordination assemblies is the main objective of the investigations described here. Special interest is directed towards dinuclear complexes with bis(benzene-l,2-dithiolato) ligands, which might be able to form helical structures. Bis(benzene-l,2-dithiolato) ligands are accessible by ortho-functionalization and subsequent linkage of two benzene-l,2-dithiol units.

On the prospects of polynuclear complexes with acetylenedithiolate bridging units.

The generation of polynuclear complexes with one, two, or four acetylenedithiolate bridging units via the isolation of eta2-alkyne complexes of acetylenedithiolate K[Tp'M(CO)(L)(C2S2)] (Tp'=hydrotris(3,5-dimethylpyrazolyl)borate, M=W, L=CO (K-3a), M=Mo, L=CNC6H3Me2 (K-3b)) is reported. The strong electronic cooperation of Ru and W in the heterobimetallic complexes [(eta5-C5H5)(PPh3)Ru(3a)] (4a) and [(eta5-C5H5)(Me2C6H3NC)Ru(3a)] (4b) has been elucidated by correlation of the NMR, IR, UV-vis, and EPR-spectroscopic properties of the redox couples 4a/4a+ and 4b/4b+ with results from density functional calculations. Treatment of M(II) (M=Ni, Pd, Pt) with K-3a and K-3b afforded the homoleptic bis complexes [M(3a)2] (M=Ni (5a), Pd (5b), Pt (5c)), and [M(3b)2] (M=Pd (6a) and Pt (6b)), in which the metalla-acetylendithiolates exclusively serve as S,S'-chelate ligands.

Acetylenedithiolate: alkyne complex formation renders it a dithiolate chelate ligand.

The isostructural complexes [{Tp'W(CO)(2)(eta(2)-C(2)S(2))}(2)M] (M = Ni, Pd, Pt) show that the eta(2)-C,C'-alkyne complexes of acetylenedithiolate at [Tp'W(CO)(2)](+) can generally act as dithiolate chelate ligands, leading to dithiolene type complexes.