Synthesis and Crystal Structures of Novel Copper(I) Clusters with Bridging Silyl Amide Ligands

Treatment of copper(I) chloride with R₂Si(NLiPh)₂ (R = Me, Ph) in thf led to the formation of the octanuclear cluster compounds [Cu₈{(R₂Si(NPh)₂}₄] [R = Me ( 1 ), Ph ( 2 ).] Compound 1 crystallizes in the tetragonal space group P4/n, with a = 1505.41(5) and c = 1911.32(7) pm. The X‐ray crystal structure determination revealed a cube shaped Cu₈ cluster core with μ₄ bridging Me₂Si(NPh)₂^2– ligands. The copper atoms display an almost linear coordination with Cu–N distances in the range of 191.1(3)–191.4(3) pm. The Cu–Cu distances are 265.7(1)–267.3(1) pm. Compound 2 forms monoclinic crystals, space group P2₁/n, with a = 1461.87(4), b = 2483.77(6), c = 2725.49(8) pm, β = 100.77(1)°. The cluster core of compound 2 consists formally of two mutually perpendicular arranged trigonal prisms, which share a common square face. Like in the case of compound 1 the square faces of the cluster core are capped by μ₄ bridging Ph₂Si(NPh)₂^2– ligands. The copper atoms adopt a nearly linear N–Cu–N coordination with Cu–N distances of 190.0(4)–195.1(4) pm. The Cu–Cu distances are 252.3(1)–305.6(1) pm.     

Dinuclear Molybdenum(II) Complexes with Thioether Functionalized Silylamide Ligands

Treatment of molybdenum(II) acetate with thioether functionalized silylamides R₂Si(NLi-C₆H₄–2-SR')₂ leads to the formation of dinuclear Mo^II complexes [Mo₂{R₂Si(NC₆H₄-2-SR')₂}₂]. According to X-ray crystal structure analyses the complexes [Mo₂{Me₂Si(NC₆H₄-2-SMe)₂}₂] and [Mo₂{Ph₂Si(NC₆H₄-2-SPh)₂}₂] comprise a Mo₂-unit which is coordinated by two μ-κ-N,N' silylamide ligands. The coordination sphere around the molybdenum atoms consists of two amide nitrogen atoms and two thioether sulfur atoms in a distorted square-planar arrangement. The Mo-Mo distances are 211.0(1) and 211.7(1) pm, resp. In the complex [Mo₂{Ph₂Si(NC₆H₄-2-SMe)₂}₂] the silyl amide units act as tetradentate κ-N,N',S,S'chelating ligands and the Mo-Mo distance is 218.6(1) pm.     

Synthesis and Crystal Structures of Aluminum,Gallium and Indium Complexes with Chelating Me2Si(NPh)22– Ligands

The reaction of ECl₃ (E = Al, Ga) with two equivalentsof Li₂Me₂Si(NPh)₂ (in diethyl ether/n‐hexane) leads to the formation of bis‐chelate complexes [Li(OEt₂)₃][E{Me₂Si(NPh)₂}₂] (E = Al ( 1 ), Ga ( 2 )). Compounds 1 and 2 crystallize isotypically in the monoclinic system with a = 1136.42(6), b = 3267.9(1), c = 1360.37(8) pm, β = 94.320(7)° for 1 and a = 1140.88(6), b = 3261.7(2), c = 1360.20(8) pm, β = 94.641(7)° for 2 . Both the compounds display a distorted tetrahedral coordination of the central metal atom to give a spirocyclic EN₄Si₂ core. The Al–N bond lengths are in the range of186.5–186.9 pm and for the Ga–N distances values between 192.3and 193.1 pm are observed. Treatment of InCl₃ with three equivalents of Li₂Me₂Si(NPh)₂ yields the tris‐chelate [{Li(OEt₂)}₃In{Me₂Si(NPh₂)}₃] 3 . Compound 3 crystallizes in the trigonal crystal system , space group R$\bar{3}$ c with a = 1852.4(1), and c = 3300.2(2) pm. The central indium atom is coordinated by threeMe₂Si(NPh)₂^2– ligands in a distorted octahedral arrangement withIn–N bond lengths of 230.8 pm.     

Synthesis and structure of a seven electron triangular cluster complex [Mo3S4Cl3(dppe)2(PEt3]

The triangular six-electron cluster complex [Mo₃S₄Cl₄(PEt₃) _x (thf)₅] produced by the excision reaction of Mo₃S₇Cl₄ with triethypholsphine is reduced by magnesium at – 20°C. Subsequent addition of dppe (=1,2-his(diphenylphosphino)ethane) to the reduced species affords a seven-electron triangular cluster complex [Mo₃S₄Cl₃(dppe)₂(PEt₃)]. The complex crystallizes in the space groupCm witha=17.170(6),b-19.878(6),c = 13.289(5) = 121.73(2)°,V = 3858(2) A³, andZ = 2. The structure shows an almost equilateral triangle of three molybdenum atoms capped by a Sulfur atom and bridged by three sulfur atoms. The Mo Mo distances, ranging from 2.804(1) to 2.809(1) A are elongated ca. 0.04 A as compared with lose of a six-electron cluster complex with drape ligands. Two molybdenum atoms have a chlorine and a dppe ligands, and the other molybdenum atom bas a chlorine and a triethylphosphine ligands. The UV-Vis spectrum has a characteristic broad hand centered at 1410 n m, which is not observed for six-electron clusters. The ESR spectrum indicates the presence of an unpaired electron consistent with the formulation of the compound as a seven-electron cluster.Dedicated to Professor fiaxi Lu on the occasion of his 80th birthday.     

Mechanistic insight into the reactivity of oxotransferases by novel asymmetric dioxomolybdenum(VI) model complexes

The asymmetric molybdenum(VI) dioxo complexes of the bis(phenolate) ligands 1,4‐bis(2‐hydroxybenzyl)‐1,4‐diazepane, 1,4‐bis(2‐hydroxy‐4‐methylbenzyl)‐1,4‐diazepane, 1,4‐bis(2‐hydroxy‐3,5‐dimethylbenzyl)‐1,4‐diazepane, 1,4‐bis(2‐hydroxy‐3,5‐di‐tert‐butylbenzyl)‐1,4‐diazepane, 1,4‐bis(2‐hydroxy‐4‐flurobenzyl)‐1,4‐diazepane, and 1,4‐bis(2‐hydroxy‐4‐chlorobenzyl)‐1,4‐diazepane (H₂(L1)–H₂(L6), respectively) have been isolated and studied as functional models for molybdenum oxotransferase enzymes. These complexes have been characterized as asymmetric complexes of type [MoO₂(L)] 1–6 by using NMR spectroscopy, mass spectrometry, elemental analysis, and electrochemical methods. The molecular structures of [MoO₂(L)] 1–4 have been successfully determined by single‐crystal X‐ray diffraction analyses, which show them to exhibit a distorted octahedral coordination geometry around molybdenum(VI) in an asymmetrical cis‐β configuration. The Mo? O_oxo bond lengths differ only by ≈0.01 Å. Complexes 1 , 2 , 5 , and 6 exhibit two successive Mo^VI/Mo^V (E_1/2, ?1.141 to ?1.848 V) and Mo^V/Mo^IV (E_1/2, ?1.531 to ?2.114 V) redox processes. However, only the Mo^VI/Mo^V redox couple was observed for 3 and 4 , suggesting that the subsequent reduction of the molybdenum(V) species is difficult. Complexes 1 , 2 , 5 , and 6 elicit efficient catalytic oxygen‐atom transfer (OAT) from dimethylsulfoxide (DMSO) to PMe₃ at 65 °C at a significantly faster rate than the symmetric molybdenum(VI) complexes of the analogous linear bis(phenolate) ligands known so far to exhibit OAT reactions at a higher temperature (130 °C). However, complexes 3 and 4 fail to perform the OAT reaction from DMSO to PMe₃ at 65 °C. DFT/B3LYP calculations on the OAT mechanism reveal a strong trans effect.     

Sn4.4Mo24O38

The single‐crystal structure of tetratin tetracosa­molybdenum octatriaconta­oxide, Sn_4.4Mo₂₄O₃₈, contains infinite chains of centrosymmetric dioctahedral Mo₁₀ and centrosymmetric trioctahedral Mo₁₄ clusters. These clusters, as well as the O atoms, the arrangement of which derives from a closest‐packing with the layer sequence …ABAC…, form sheets parallel to the ac plane of the monoclinic unit cell. The Mo—Mo distances range from 2.6225 (7) to 2.8212 (9) Å and from 2.6270 (7) to 2.8365 (7) Å in the Mo₁₀ and Mo₁₄ clusters, respectively. The Mo—O distances vary between 1.949 (4) and 2.151 (4) Å in the Mo₁₀ cluster and between 1.938 (4) and 2.140 (4) Å in the Mo₁₄ cluster. The three crystallographically independent Sn²⁺ ions are off the centre of distorted oxy­gen octahedra.     

High Intensity Trip-Multiplet Transitions,a Reality! Synthesis,Properties, and Crystal Structure of l-Bis(triphenylphosphine)iminium trans-Dibromophthalocyaninato(2–)molybdate(III)

Oxophthalocyaninato(2–)molybdenum(IV), activated by bromine oxidation prior to use, reacts with fused triphenylphosphine in the presence of bis(triphenylphosphine)iminium bromide to yield linear-bis(triphenylphosphine)iminium trans-dibromophthalocyaninato(2–)molybdate(III), ^l(PNP)^trans[Mo(Br)₂pc^2?]. It crystallizes triclinic with crystal data: a = 10.506(1) Å, b = 12.436(2) Å, c = 12.918(2) Å, α = 76.186(1)°, β = 67.890(1)°, γ = 68.689(1)°; space group P1 (No. 2); Z = 1. Mo^III is in a pseudo-octahedral coordination geometry with the bromo ligands in trans-arrangement. The Mo? N_p and Mo? Br distance is 2.043(10) and 2.588(1) Å, respectively. The PNP cation adopts a linear conformation. In the IR spectrum v_as(Mo? Br) is observed at 218 cm^?1 and v_as(P? N) of the linear (P? N? P) core at 1406 cm^?1. Cyclic and differential-pulse voltammetry show two quasi-reversible cathodic processes at ?1.15 and ?0.53 V vs. Ag/AgCl. The first is assigned to a phthalocyaninate directed reduction (pc^2?/pc^3?), while the latter arises from a Mo directed reduction (Mo^III/Mo^II). Spectral monitoring confirms the reversible Mo^III/Mo^II reduction. Two quasi-reversible anodic processes at 0.60 and 1.27 V are assigned to the successive Mo directed oxidation with redox couples Mo^III/Mo^IV and Mo^IV/Mo^V. For the first time, three very intense spin-allowed trip-quartet transitions are observed in the electronic absorption spectra at 7140 (TQI), 16890 (TQ2) and 18700 cm^?1 (TQ3) together with a sing-quartet transition at 15850 cm^?1 and characteristic ?Q”? region with maximum at 28500 cm^?1 and ?N”? region at 37400 cm^?1. All electronic excitations are of comparable intensity. A prominent low temperature emission at 6690 cm^?1 is assigned to a spin-forbidden trip-sextet.     

N,N-Dimethylglycinatokomplexe von Platin(IV)

N,N -Dimethylglycinato Complexes of Platinum(IV) The aquapentachloroplatinic acid (H₃O)-[PtCl₅(H₂O)] · 2(18-cr-6) · 6 H₂O ( 1 ) reacts with N,N-dimethylglycine (Me₂glyH) to give cis-[PtCl₂(N,O-Me₂gly)₂] · (18-cr-6) ( 6 ) and (Me₂glyH₂)[PtCl₄(N,O-Me₂gly)] ( 7 ). Complexes 6 and 7 are characterized by microanalysis, ¹H-NMR and IR spectroscopy as well as by X-ray structure analysis. In both complexes the N,N-dimethylglycinato ligands are N,O-coordinated. In 6 , the amino groups are mutually trans and the carboxylato groups are cis (configuration index: OC-6–22). In the crystal, there are only weak C–H…O interactions between the N-methyl groups of the [PtCl₂(N,O-Me₂gly)₂] complex and the oxygen atoms of the crown ether (shortest C…O contacts: 3.10(2) Å and 3.21(2) Å). In the solid state, 7 exhibits strong cation-anion interactions: The carboxyl group of the cation (Me₂glyH₂)⁺ forms a strong O–H…O bridge to the exocyclic oxygen atom of the carboxylate group of the glycinato ligand (O…O 2.61(1) Å).     

Aminobis(phenolate)s of imidomolybdenum(VI) and -tungsten(VI)

The reactions of trans-[MoO(ONO^Me)Cl₂] 1 (ONO^Me = methylamino-N,N-bis(2-methylene-4,6-dimethylphenolate) dianion) and trans-[MoO(ONO^tBu)Cl₂] 2 (ONO^tBu = methylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenolate) dianion) with PhNCO afforded new imido molybdenum complexes trans-[Mo(NPh)(ONO^Me)Cl₂] 3 and trans-[Mo(NPh)(ONO^tBu)Cl₂] 4, respectively. As analogous oxotungsten starting materials did not show similar reactivity, corresponding imido tungsten complexes were prepared by the reaction between [W(NPh)Cl₄] with aminobis(phenol)s. These reactions yielded cis- and trans-isomers of dichloro complexes [W(NPh)(ONO^Me)Cl₂] 5 and [W(NPh)(ONO^tBu)Cl₂] 6, respectively. The molecular structures of 4, cis-6 and trans-6 were verified by X-ray crystallography. Organosubstituted imido tungsten(VI) complex cis-[W(NPh)(ONO^tBu)Me₂] 7 was prepared by the transmetallation reaction of 6 (either cis or trans isomer) with methyl magnesium iodide.     

Synthese und Röntgenstrukturanalyse von Bis(2,2,6,6-tetramethylpiperidin-1-oxidato-O,N)-molybdän(VI)-dioxid

Synthesis and X-Ray Structure Analysis of Bis(2,2,6,6-tetramethylpiperidine-1-oxidato-O,N)molybdenum (VI) Dioxide The title compound ( 1 ) was synthesized by a photoreaction of the 2,2,6,6-tetramethylpiperidin-1-oxyl [TMPO] radical with Mo(CO)₆ and characterized by an X-ray structure analysis as (TMPO)₂MoO₂ complex. In the coordinatively unsaturated 16 electron compound of mm2 symmetry the Mo^VI is coordinated nearly tetrahedrally by the four ligands, the TMPO^? ligands being O,N coordinated. The Mo? O, Mo? N, and Mo?O distances are 1.972(3), 2.198(3), and 1.711(2) Å respectively; the N? O distances are 1.436(4) Å. The stereochemistry of the Mo coordination is the same as in other (R₂NO)₂MoO₂ complexes.     

Dinitrogen‐Molybdenum Complex Induces Dinitrogen Cleavage by One‐Electron Oxidation

Reported here is the N₂ cleavage of a one‐electron oxidation reaction using trans‐[Mo(depe)₂(N₂)₂] ( 1 ) (depe=Et₂PCH₂CH₂PEt₂), which is a classical molybdenum(0)‐dinitrogen complex supported by two bidentate phosphine ligands. The molybdenum(IV) terminal nitride complex [Mo(depe)₂N][BArf₄] ( 2 ) (BArf₄=B(3,5‐(CF₃)₂C₆H₃)₄) is synthesized by the one‐electron oxidation of 1 upon addition of a mild oxidant, [Cp₂Fe][BArf₄] (Cp=C₅H₅), and proceeds by N₂ cleavage from a Mo^II‐N=N‐Mo^II structure. In addition, the electrochemical oxidation reaction for 1 also cleaved the N₂ ligand to give 2 . The dimeric Mo complex with a bridging N₂ is detected by in situ resonance Raman and in situ UV‐vis spectroscopies during the electrochemical oxidation reaction for 1 . Density‐functional theory (DFT) calculations reveal that the unstable monomeric oxidized Mo^I species is converted into 2 via the dimeric structure involving a zigzag transition state.     

A new cluster complex, (NH4)6[Mo4Se4(CN)12]·6H2O,containing a tetranuclear mixed‐valence molybdenum core

The title compound, hexa­ammonium tetra‐μ₃‐selenido‐tetra­kis­(tri­cyano­molybdenum) hexahydrate, is isostructural with the Mo/S, W/S and W/Se analogues. The structure contains disordered cyclic hydrogen‐bonded [{(NH₄)(H₂O)}₃]³⁺ cations and [Mo₄Se₄(CN)₁₂]^6? cluster anions with 3m symmetry. The cation assembly consists of alternating ammonium and water mol­ecules linked by N—H?O hydrogen bonds. The anion has a typical cubane cluster structure. The cations and anions are linked together by hydrogen bonds involving the terminal N atoms of the CN groups.     

Ag2.54Tl2Mo12Se15: a new structure type containing Mo6 and Mo9 clusters

The novel structure‐type Ag_2.54Tl₂Mo₁₂Se₁₅ (silver thallium molybdenum selenide) is built up of Mo₆Seⁱ₈Se^a₆ and Mo₉Seⁱ₁₁Se^a₆ cluster units in a 1:2 ratio, which are three‐dimensionally connected to form the Mo–Se network. The Ag and Tl cations are distributed in several voids within the cluster network. Three of the seven independent Se atoms and one Tl atom lie on sites with 3.. symmetry (Wyckoff sites 2c or 2d).     

Synthese und Struktur von zwei- und dreikernigen Heterometallkomplexen mit Nitridobrücken zwischen Re und Mo

Synthesis and Structure of Two- and Threenuclear Heterometallic Complexes with Nitrido Bridges between Re and Mo The reaction of ReNCl₂(PMe₂Ph)₃ with MoCl₄(NCEt)₂ yields the heterometallic threenuclear complex [{(Me₂PhP)₃(EtCN)ClRe≡N–}₂MoCl₄][MoNCl₅]. The anion [MoNCl₅]^2– presumably results from a transfer of the nitrido ligand from the Re to the Mo atom. The air-sensitive compound is paramagnetic with μ_eff = 2.87 B. M. at room temperature. A reduction of the magnetic moment to 1.74 B.M at 20 K starts at 140 K. The complex crystallizes in the orthorhombic space group Pca2₁ with a = 2430(1), b = 1328(1), c = 2436.3(2) pm, Z = 4. With bond angles Re–N–Mo of 164° and 167° the nitrido bridges are almost linear. The distances Re–N of 169 and 170 pm can be interpreted with triple bonds. The Mo–N bond lengths of 210 and 211 pm correspond to single bonds. In the anion [MoNCl₅]^2– the distance Mo≡N is 167 pm. Hydrolysis of the threenuclear complex results in a cleavage of one of the nitrido bridges to yield (Me₂PhP)₃(EtCN)ClRe≡N–MoOCl₄. The compound is paramagnetic with μ_eff = 1.71 B.M. at room temperature. It crystallizes in the orthorhombic space group Pbca with a = 1718.5(4), b = 2037(1), c = 2041.1(7) pm, Z = 8. In the dinuclear complex the [MoOCl₄]^– unit is only weakly coordinated to the nitrido ligand with Mo–N = 246.5 pm, while the distance of the Re≡N bond of 168.1 pm is almost unchanged in comparison with a terminal bond. The bond angle Re≡N–Mo is 165.6°.     

First Bis(σ)-borane Complexes of Group 6 Transition Metals: Experimental and Theoretical Studies

A series of bis(σ)-borane complexes of Group 6 transition metals were prepared by direct dihydroborane coordination to the metal center. Reaction of [M(CO)₃(PCy₃)₂] and two dihydroboranes [DurBH₂] and [(Me₃Si)₂NBH₂] (Dur=2,3,5,6-Me₄C₆H) yielded bis(σ)-borane complexes fac-[M(CO)₃(PCy₃){η²-(H₂BR)}] (R=Dur; 1 : M=Cr, 2 : M=W; R=N(SiMe₃)₂; 3 : M=Cr, 4 : M=W). In the case of molybdenum, we have isolated an arene complex ( 5 ) with [DurBH₂] in which the Dur group acts as a η⁶-bound ligand, and with [(Me₃Si)₂NBH₂] a similar bis(σ)-borane complex was isolated, cis,trans-[Mo(CO)₂(PCy₃)₂{η²-(H₂BN(SiMe₃)₂}] ( 6 ), with a different pattern of auxiliary ligands. The complexes were investigated by multinuclear NMR spectroscopy, mass spectrometry, X-ray diffraction analysis, and computational methods. Quantum theory of atoms in molecules (QTAIM) calculations demonstrated that the borane complexes may be described as pure bis(σ)-borane complexes rather than elongated or stretched examples given that the calculations do not show the presence of a ring-critical point (RCP) at the ring formed by the interactions of the B−H with metal center.     

Darstellung,Eigenschaften und Reaktionsverhalten von 2-(Dimethylaminomethyl)phenyl- und 8-(Dimethylamino)naphthylsubstituierten Lithiumhydridosilylamiden – Bildung von Silaniminen durch Lithiumhydrideliminierung

Preparation, Properties, and Reaction Behaviour of 2-(Dimethylaminomethyl)phenyl- and 8-(Dimethylamino)naphthylsubstituted Lithium Hydridosilylamides – Formation of Silanimines by Elimination of Lithium Hydride The hydridosilylamines Ar(R)Si(H)–NHR′ ( 2 a : Ar = 2-Me₂NCH₂C₆H₄, R = Me, R′ = CMe₃; 2 b : Ar = 2-Me₂NCH₂C₆H₄, R = Ph, R′ = CMe₃; 2 c : Ar = 2-Me₂NCH₂C₆H₄, R = Me, R′ = SiMe₃; 2 d : Ar = 8-Me₂NC₁₀H₆, R = Me, R′ = CMe₃; 2 e : Ar = 8-Me₂NC₁₀H₆, R = Ph, R′ = CMe₃; 2 f : Ar = 8-Me₂NC₁₀H₆, R = Me, R′ = SiMe₃) have been synthesized from the appropriate chlorosilanes Ar(R)SiHCl either by reaction with the stoichiometric amount of Me₃CNHLi ( 2 a , 2 b , 2 d , 2 e ) or by coammonolysis in liquid NH₃ with chlorotrimethylsilane in molar ratio 1 : 3 ( 2 c , 2 f ). Treatment of 2 a–2 f with n-butyllithium in equimolar ratio in n-hexane resulted in the lithiumhydridosilylamides Ar(R)Si(H)–N(Li)R′ 3 a–3 f . The frequencies of the Si–H stretching vibration and ²⁹Si–¹H coupling constants in the amides are smaller than in the analogous amines indicating a higher hydride character for the hydrogen atom of the Si–H group in the amides compared to the amines. Results of NMR spectroscopic studies point to the existence of a (Me₂)N → Si coordination bond in the 8-(dimethylamino)naphthyl-substituted amines and amides. The amides 3 a–3 c are stable under refluxing in m-xylene. At the same conditions 3 d and 3 e eliminate LiH and the silanimines 8-Me₂NC₁₀H₆(R)Si=NCMe₃ ( 4 d : R = Me, 4 e : R = Ph) are formed. The amides 3 a–3 d und 3 f react with chlorotrimethylsilane in THF to give the corresponding N-substitution products Ar(R)Si(H)–N(SiMe₃)R′ 6 a–6 d and 6 f in good yields. 4 d is formed as a byproduct in the reaction of 3 d with chlorotrimethylsilane. In n-hexane and m-xylene these amides are little reactive opposite to chlorotrimethylsilane. 6 a–6 d and 6 f are obtained in very small amounts. In the case of 3 d besides the N-substitution product 6 d the silanimine 4 d is obtained. In contrast to chlorotrimethylsilane the amides 3 a and 3 f react well with chlorodimethylsilane in m-xylene producing 2-Me₂NCH₂C₆H₄(H) SiMe–N(SiHMe₂)CMe₃ ( 7 a ) and 8-Me₂NC₁₀H₆(H)SiMe–N(SiHMe₂)SiMe₃ ( 7 f ).     

Synthesis,structures, and electrocatalytic properties of phosphine-monodentate, −chelate,and -bridge diiron 2,2-dimethylpropanedithiolate complexes related to [FeFe]-hydrogenases

To further extend diiron subsite models of [FeFe]-hydrogenases, the various substitutions of all-carbonyl diiron complex Fe₂(μ-Me₂pdt)(CO)₆ ( A , Me₂pdt = (SCH₂)₂CMe₂) with monophosphines or small bite-angle diphosphines are studied as follows. Firstly, the monodentate complexes Fe₂(μ-Me₂pdt)(CO)₅{κ¹-P(C₆H₄R-p)₃} [R = Me ( 1a ) and Cl ( 1b )] and Fe₂(μ-Me₂pdt)(CO)₅{κ¹-Ph₂PX'} [X' = NHPh ( 2a ) and CH₂PPh₂ ( 2b )] are readily afforded through the Me₃NO-assisted reactions of A with monophosphines P(C₆H₄R-p)₃ (R = Me, Cl) and diphosphines (Ph₂P)₂X (X = NPh, CH₂ (dppm)) in MeCN at room temperature, respectively. Secondly, the chelate complexes Fe₂(μ-Me₂pdt)(CO)₄(κ²-(Ph₂P)₂X) [X = NPh ( 3a ) and NBuⁿ ( 3b )] can be efficiently prepared by the UV-irradiated reactions of A with small bite-angle diphosphines (Ph₂P)₂X (X = NPh, NBuⁿ) in toluene. Thirdly, the bridge complexes Fe₂(μ-Me₂pdt)(CO)₄(μ-(Ph₂P)₂X) [X = NPh ( 4a ) and CH₂ ( 4b )] are well obtained from the refluxing solutions of A and diphosphines (Ph₂P)₂X (X = NPh, CH₂) in xylene. Rarely, the diphosphine-bridge complex 4b may be produced in low yield via the UV-irradiated solutions of A and the dppm ligand in toluene emitting at 365 nm. Eight new complexes obtained above have been well characterized by using element analysis, FT-IR, NMR (¹H, ³¹P) spectroscopies, and particularly for 1a , 1b , 2a , 3b , 4a , 4b by X-ray crystallography. Meanwhile, the electrochemical and electrocatalytic properties of three representative complexes 2a , 3a , and 4a with pendant N-phenyl groups are investigated and compared by using cyclic voltammetry (CV) in the absence and presence of trifluoroacetic acid (TFA) as a proton source, indicating that they are all found to be active for electrocatalytic proton reduction to hydrogen (H₂).     

Synthesis,Crystal Structure,and Luminescence of Metal Iodide Cluster Compounds (nBu4N)2[M6I8(NCO)6] with M = Mo,W

Molybdenum and tungsten iodide clusters with the [M₆I₈] cluster core show versatile photophysical properties that strongly depend on the nature of six apical ligands (L) in [M₆I₈L₆]^2–. In course of our syntheses we report a new efficient preparation of Cs₂[Mo₆I₁₄] as precursor. Target compounds (ⁿBu₄N)₂[M₆I₈(NCO)₆] with M = Mo, W with cyanate ligands were synthesized and structurally characterized to study their photophysical properties. (ⁿBu₄N)₂[M₆I₈(NCO)₆] compounds appear as deep red (Mo) and light yellow (W) crystal powders showing strong phosphorescence. Compared to other cluster compounds of this type there is no significant concentration quenching obtained by the presence of molecular oxygen.     

A trinuclear Mo-Fe-Mo cluster compound [Et_4N] { [Me_2dtcMo-O(μ-S)_2]_2Fe} containing dialkyldithiocarbamate ligand

A trinuclear linear Mo-Fe-Mo dialkyldithiocarbamate complex [Et4N] { [ Me2dtcMoO (μ-S)2 ]2Fe} has been obtained and structurally characterized, which contains two Me2dtcMoO-(μ-S)2 units coordinated to a central tetrahedral Fe atom. A comparison of the structural parameters indicates the metal oxidation states of 2Mo(v) Fe(III). The 1H NMR shows chemical shifts of Me2dtc ligands at 5 10.14 and 8 9.40 with the intensity ratio of 1:1. The cyclic voltammogram displays a reversible couple at - 1.41 V/ - 1.36 V responsible for 1-/2-anions of the complex and an irreversible oxidation at 0.5 V, which seems to show the apparent lack of stability for its neutral species (Me2dtcMoOS2)2Fe.     

Synthesis and Complexation Study of New Aminoalkynyl−amidinate Ligands

The current library of amidinate ligands has been extended by the synthesis of two novel dimethylamino-substituted alkynylamidinate anions of the composition [Me₂N−CH₂−C≡C−C(NR)₂]⁻ (R = ⁱPr, cyclohexyl (Cy)). The unsolvated lithium derivatives Li[Me₂N−CH₂−C≡C−C(NR)₂] ( 1 : R = ⁱPr, 2 : R = Cy) were obtained in good yields by treatment of in situ-prepared Me₂N−CH₂−C≡C−Li with the respective carbodiimides, R−N=C=N−R. Recrystallization of 1 and 2 from THF afforded the crystalline THF adducts Li[Me₂N−CH₂−C≡C−C(NR)₂] ⋅ nTHF ( 1 a : R = ⁱPr, n=1; 2 a : R = Cy, n=1.5). Precursor 2 was subsequently used to study initial complexation reactions with selected di- and trivalent transition metals. The dark red homoleptic vanadium(III) tris(alkynylamidinate) complex V[Me₂N−CH₂−C≡C−C(NCy)₂]₃ ( 3 ) was prepared by reaction of VCl₃(THF)₃ with 3 equiv. of 2 (75 % yield). A salt-metathesis reaction of 2 with anhydrous FeCl₂ in a molar ratio of 2 : 1 afforded the dinuclear homoleptic iron(II) alkynylamidinate complex Fe₂[Me₂N−CH₂−C≡C−C(NCy)₂]₄ ( 4 ) in 69 % isolated yield. Similarly, treatment of Mo₂(OAc)₄ with 3 or 4 equiv. of 2 provided the dinuclear, heteroleptic molybdenum(II) amidinate complex Mo₂(OAc)[Me₂N−CH₂−C≡C−C(NCy)₂]₃ ( 5 ; yellow crystals, 50 % isolated yield). The cyclohexyl-substituted title compounds 2 a , 4 , and 5 were structurally characterized through single-crystal X-ray diffraction studies.