Reactions of the cycloheptatrienyl complexes [MX(CO)2(η-C7H7)] (M=Mo, X=Br; M=W, X=I) with CNBu: X-ray crystal structure of [WI(CO)2(CNBu)2(η-C7H7)]

Reaction of [MX(CO)₂(η⁷-C₇H₇)] (M=Mo, X=Br; M=W, X=I) with two equivalents of CNBu^t in toluene affords the trihapto-bonded cycloheptatrienyl complexes [MX(CO)₂(CNBu^t)₂(η³-C₇H₇)] (1, M=Mo, X=Br; 2, M=W, X=I). The X-ray crystal structure of 2 reveals a pseudo-octahedral molecular geometry with an asymmetric ligand arrangement at tungsten in which one CNBu^t is located trans to the η³-C₇H₇ ring. Treatment of 2 with tetracyanoethene results in 1,4-cycloaddition at the η³-C₇H₇ ring to give [WI(CO)₂(CNBu^t)₂{η³-C₉H₇(CN)₄}], 3. The principal reaction type of the molybdenum complex 1 is loss of carbonyl and bromide ligands to afford substituted products [MoBr(CNBu^t)₂(η⁷-C₇H₇)] 4 or [Mo(CO)(CNBu^t)₂(η⁷-C₇H₇)]Br. Reaction of [MoBr(CO)₂(η⁷-C₇H₇)] with one equivalent of CNBu^t in toluene at 60°C affords [MoBr(CO)(CNBu^t)(η⁷-C₇H₇)], 5, which is a precursor to [Mo(CO)(CNBu^t)(NCMe)(η⁷-C₇H₇)][BF₄], 6, by reaction with Ag[BF₄] in acetonitrile. In contrast with the parent dicarbonyl systems [MoX(CO)₂(η⁷-C₇H₇)], complexes of the Mo(CO)(CNBu^t)(η⁷-C₇H₇) auxiliary, 5 and 6, do not afford observable η³-C₇H₇ products by ligand addition at the molybdenum centre.     

Preparative use of electrode catalyzed substitution reactions; synthesis of Fe(CO)(PPh3)(η-C5H5)COCH3

It is shown that electrode catalysis of substitution reactions can operate even for systems with rather slow chemical steps and, furthermore, for those which are electrochemically irreversible. A procedure is described for synthesis of Fe(CO)(PPh₃)(η⁵-C₅H₅)COCH₃ from Fe(CO)₂(η⁵-C₅H₅)CH₃ and triphenylphosphine. A simplified mechanism for the catalytic chain, is given and discussed in terms of the structure of the reacting species.     

The reactions of [Co(η-C5H5)(CO)(L)] (L = R3P or RNC) with carbon disuphide and organoisothiocyanates

The reactions of [Co(η-C₅H₅)(CO)(PR₃)] or [Co(η-C₅GH₅)(CO)₂]/R₃P mixtures (R = alkyl or aryl) with CS₂ in refluxing CS₂ or CS₂/toluene gives rise to [Co(η-C₅H₅)(PR₃)(CS)], [Co(η-C₅H₅)(PR₃)(CS₂)], [Co(η-C₅H₅)(PR₃)(CS₃)], and [Co₃(η-C₅H₅)₃ (CS)(S)] in reasonable yields. The corresponding reactions using PhNCS give [Co(η-C₅H₅)(PPh₃)(PhNCS)] and a polymeric species which appears to be [Co₄(η-C₅H₅)₄ (PhNCS)]. Similar products are obtained with [Co(η-C₅H₅)(CO)(CNR)] or [Co(η0C₅H₅)(CO)₂]/RNC mixtures.     

A novel cis-push–pull effect in cycloruthenated azobenzene thiocarbonyl-containing complexes: crystal and molecular structures of [RuX(CS)(η-C,N-C6H4N=NPh)(PPh3)2](X=Cl, I)

Treatment of [RuHCl(CS)(PPh₃)₃] with Hg(o-C₆H₄N=NC₆H₅)₂ affords [RuCl(CS)(η²C,N-o-C₆H₄N=NC₆H₅)(PPh₃)₂] (1) in good yield, where the cyclometallated azobenzene ligand coordinates through an ortho-C and one azo-N to give a five-membered chelate ring. Reaction of 1 with AgNO₃ followed by NaBr or NaI affords the chloride-exchanged products [RuX(CO)(η²C,N-o-C₆H₄N=NC₆H₅)(PPh₃)₂] (2, 3), whereas reaction of 1 with AgOC(O)Me or NaS₂CNEt₂·2H₂O gives the halide mono-phosphine-substituted complexes [Ru(CS)(LL)(η²C,N-o-C₆H₄NNC₆H₅)(PPh₃)] (4, 5). In the solid-state structures of 1 and 3 there are significant changes in the bond lengths for the cyclometallated azobenzene ligand are observed relative to free azobenzene. These are discussed, with the aid of spectroscopic and crystallographic data, in terms of a cis-push–pull effect.     

η-Alkynyl and vinylidene transition metal complexes: 10. Reaction of the metal-acetylide [(η-C5H5)(CO)(NO)W---CC---C(CH3)3]Li with 1,2-diiodoethane as electrophile and with various nucleophiles

Treatment of the η¹-acetylide complex [(η⁵-C₅H₅)(CO)(NO)W---CC---C(CH₃)₃]Li (4) with 1,2-diiodoethane in THF at −78 °C, followed by the addition of Li---CC---R [R=C(CH₃)₃, C₆H₅, Si(CH₃)₃, 6a–6c] or n-C₄H₉Li and protonation with H₂O, afforded the corresponding oxametallacyclopentadienyl complexes (η⁵-C₅H₅)W(I)(NO)[η²-O=C(CC---R)CH=CC(CH₃)₃] (7a–7c), 8c and (η⁵-C₅H₅)W(I)(NO)[η²-O=C(n-C₄H₉)CH=CC(CH₃)₃] (9). The formation of these metallafuran derivatives is rationalized by the electrophilic attack of 1,2-diiodoethane onto the metal center of 4 to form first the neutral complex [(η⁵-C₅H₅)(I)(CO)(NO)W---CC---C(CH₃)₃] (5). Subsequent nucleophilic addition of Li---CC---R 6a–6c or n-C₄H₉Li and a reductive elimination step followed by protonation leads to the products 7a–7c and 9. One reaction intermediate could be trapped with CF₃SO₃CH₃ and characterized by a crystal structure analysis. The identity of another intermediate was established by infrared spectroscopic data. The oxametallacyclopentadienyl complex 10 forms in the presence of excess 1,2-diiodoethane through an alternative pathway and crystallizes as a clathrate containing iodine.     

The transition metal catalysed reaction between η-C5H5Mo(CO)3I and isonitriles

The reaction betweeen (η⁵-C₅H₅Mo(CO)₃I and RNC is catalysed by [η⁵ -C₅H₅Mo(CO)₃]₂ and readily yields η⁵-C₅H₅Mo(CO)_3−n(RNC)_nI (n = 1–3). A free radical mechanism is consistent with experimental data.     

Unusual stabilization of cationic “M(η-allyl) (M = Pt, Pd) units by a dianionic cis-{Pt(C6F5)2(CCSiMe3)2} fragment

Chloride abstraction from [{M(η³ --- C₃H₅)Cl}_n] (M = Pt, n = 4 or M = Pd, n = 2) by (NBu₄)₂[cis-Pt(C₆F₅)₂(CCSiMe₃)₂] (1) gives rise to novel homo- and hetero-dinuclear zwitterionic derivatives (NBu₄) [{cis-Pt(C₆F₅)₂(CCSiMe₃)₂}M(η³-C₃H₅)] (M = Pt 2; M = Pd 3) which are formed by a M(η³-allyl)⁺ unit attached to both alkynyl ligands of the {cis-Pt(C₆F₅)₂(CCSiMe₃)₂}²⁻ fragment. The structure of 3 has been established by X-ray diffraction.     

Syntheses and crystal structures of linear coordinated complexes of Ag with the ligands C(PPh3)2 and (HC{PPh3}2)

The cationic complexes [({Ph₃P}₂C)Ag(C{PPh₃}₂)]X (2⁺, X = Cl, BF₄) with a linear arrangement of the ligands were obtained from the reaction of C(PPh₃)₂ (1) with the appropriate AgX in THF. The ³¹P NMR spectrum of the cation 2⁺ exhibits a doublet with J(Ag,P) = 15.3 Hz. The cation was also formed when the adduct O₂C ← 1 was allowed to react with AgX in CH₂Cl₂ in the first step as shown by ³¹P NMR; however, deprotonation of the solvent finally produced the cation (HC{PPh₃}₂)⁺, (H1)⁺ quantitatively. In the absence of coordinating anions, the tricationic complex [({Ph₃P}₂CH)Ag(CH{PPh₃}₂)](BF₄)₃ (3), containing the cation (H1)⁺ as ligand, could be isolated by reacting AgBF₄ with the salt (H1)(BF₄). All compounds were characterized by IR and ³¹P NMR spectroscopy; the structures of the compounds [2]Cl·1.25THF, 3·5CH₂Cl₂, 3·4C₂H₄Cl₂, and (H1)(BF₄) could be established by X-ray analyses.     

Synthesis and reactivity of new heterodinuclear iron/rhenium Cx complexes of the formula (η-C5Me5)Re(NO)(PPh3)(CC)n(η-dppe)Fe(η-C5Me5) (n = 3, 4): Redox properties and a dicobalt hexacarbonyl adduct

We report in this communication the synthesis and characterization of two Fe/Re heterodinuclear complexes 3_n of formula (η⁵-C₅Me₅)Re(NO)(PPh₃)(CC)_n(η²-dppe)Fe(η⁵-C₅Me₅) (n = 3, 4) as well as the hexacarbonyl dicobalt adduct (4) of the hexatriynediyl complex 3₃. We show by cyclic voltammetry that the “electronic communication” between the organometallic endgroups and thereby the thermodynamic stability of the corresponding mixed-valent (MV) parent 3_n⁺ is strongly influenced by bridge extension or by complexation of the [Co₂(CO)₆] fragment. In the case of the hexatriynediyl complex, the MV complex 3₃⁺ or 4 can be isolated by performing the chemical oxidation of 3₃ at low temperature. Spectroscopic studies of this compound and of other stable oxidized redox congeners should now help us to unravel how bridge extension modifies the electronic communication between the different redox-active endgroups in this family of unsymmetrically-substituted polyynediyl compounds.     

Chelate structures of 5-(H/Br)-2-hydroxybenzaldehyde-4-allyl-thiosemicarbazones (H2L): Synthesis and structural characterizations of [Ni(L)(PPh3)] and [Ru(HL)2(PPh3)2]

The reactions of 5-R-2-hydroxybenzaldehyde-4-allyl-thiosemicarbazone {R: H (L¹); Br (L²)} with [M^II(PPh₃)nCl₂] (M = Ni, n = 2 and M = Ru, n = 3) in a 1:1 molar ratio have given stable solid complexes corresponding to the general formula [Ni(L)(PPh₃)] and [Ru(HL)₂(PPh₃)₂]. While the 1:1 nickel complexes are formed from an ONS donor set of the thiosemicarbazone and the P atom of triphenylphosphine in a square planar structure, the 1:2 ruthenium complexes consist of a couple from each of N, S and P donor atoms in a distorted octahedral geometry. These mixed-ligand complexes have been characterized by elemental analysis, IR, UV–Vis, APCI-MS, ¹H and ³¹P NMR spectroscopies. The structures of [Ni(L²)(PPh₃)] (II) and [Ru(L¹H)₂(PPh₃)₂] (III) were determined by single crystal X-ray diffraction.     

Role of B(C6F5)3 in activating the nickel-methyl complex (η-C5H5)Ni(CH3)(PPh3) to initiate the vinyl polymerization of norbornene

The Ni-methyl complex (η⁵-C₅H₅)Ni(CH₃)(PPh₃) (1) reacted with B(C₆F₅)₃ to give an unstable contact ion-pair complex with a μ-methyl bridge between the Ni and B atoms. Formation of the B-CH₃ bond was confirmed by the reaction of this complex with PPh₃ to give [(η⁵-C₅H₅)Ni(PPh₃)₂][B(CH₃)(C₆F₅)₃] which was structurally characterized. Spontaneous decomposition of the contact ion-pair complex yielded (η⁵-C₅H₅)Ni(C₆F₅)(PPh₃) which is very stable and does not show any reactions with norbornene with or without added B(C₆F₅)₃. ¹⁹F NMR study showed that the polynorbornene obtained by the catalysis of 1/B(C₆F₅)₃ system has the C₆F₅ end-group. A series of reactions, which includes CH₃/C₆F₅ exchange between the Ni and B centers with concomitant dissociation of PPh₃ to accept coordination of a norbornene monomer, is proposed as the route to active species that can initiate vinyl polymerization of norbornene.     

Thiocarbonyl complexes of ruthenium(II). Synthesis of RuCl2(CS)(H2O)(PPh3)2 and RuHCl(CS)(PPh3)3

A high-yield synthesis of trans-RuCl₂(CS)(H₂O)(PPh₃)₂ from RuCl₂(PPh₃)₃ and CS₂ is described. The coordinated water molecule is labile, and introduction of CNR (R  p-toyl or p-chlorophenyl) leads to yellow trans-RuCl₂(CS)(CNR)(PPh₃)₂, which isomerises thermally to colourless cis-RuCl₂(CS)(CNR)(PPh₃)₂. Reaction of AgClO₄ with cis-RuCl₂(CS)(CNR)(PPh₃)₂ gives [RuCl(CS)(CNR)(H₂O)(PPh₃)₂]⁺, from which [RuCl(CS)(CO)(CNR)(PPh₃)₂]⁺ and [RuCl(CS)(CNR)₂(PPh₃)₂]⁺ are derived. Reaction of trans-RuCl₂(CS)(H₂O)(PPh₃)₂ with sodium formate gives Ru(η²-O₂CH)Cl(CS)(PPh₃)₂, which undergoes decarboxylation in the presence of (PPh₃) to give RuHCl(CS)(PPh₃)₃. Ru(η²-O₂CH)H(CS)(PPh₃)₂ and Ru(η²-O₂CMe)-H(CS)(PPh₃)₂ are also described.     

Complexation and aromatization of α,β-unsaturated cyclic ketones by Ru(H2O)6 and (Bz)Ru(H2O)3: molecular structure of (η-Tosylate)(η-hydroxycyclopentadienyl)Ru and of (η-Tosylate)(η-1,4-dihydroxy-2,3,5,6-tetramethylbenzene)Ru

Ruaq²⁺(OTs)₂ complexes in aqueous solution to unsaturated cyclic ketones. These aromatized on heating to π-arene Ru complexes. Thus, with cyclohexonone the main product was Ru(η⁶-phenol)₂²⁺, 4, along with some Ru(η⁶-phenol)(η⁶-OTs)⁺, 6. Similarly gave cyclopentenone in the presence of various arenes Ru(η⁵-hydroxycyclopentadienyl)(η⁶-arene)⁺. Duruquinone complexed to Ruaq²⁺ as a monoprotanated hydroquinolate in Ru(η⁶-2,3,5,6-tetramethyl-1,4-hydroquinone)(η⁶-OTs), 14. Ru(η⁵-cyclopentadienyl)(η⁶-OTs), 8, and 14 were characterized by single crystal x-ray structure analyses, data see Table 1. Whereas both ligands in 8 are planar, the 1,4-hydroquinone ligand in 14 shows distinct bending of the COH groups.     

Reactivity modes of bridged bimetallic [(η-C5H5)Fe(CO)]2-μ-dppe with electrophiles. Preparation and reactions of bimetallic hydride complexes

The complex [(η⁵-C₅H₅)Fe(CO)]₂-μ-dppe (dppe = ethane-1,2-bisdiphenylphosphide) (I) reacts with electrophiles through a η-CO and forms Lewis acid O-Adducts with alkylating reagents (giving cationic μ₂-alkoxycarbyne compounds) or with alkulaluminum compounds. Treatment of I with acid affords a stable μ₂-hydride salt (IV), [CpFe(CO)]₂(μ₂-dppe)⁺, which serves as an intermediate in the stepwise hydrogenation (reversibly) of I to a bridged bimetallic dihydride, [CpFe(CO)H]₂-μ₂-dppe. This dihydride serves as a hydride donor, regenerating IV, towards Ph₃c⁺ or CpFe(CO)₂(η²-CH₂---CH₂)⁺ hydride acceptors. The necessity of the μ₂-dppe as a “mechanical linkage” in facilitating some bimetalic reactions is also established.     

Übergangsmetall-fulven-komplexe : XXVIII. Reaktionen von (fulven)Cr(CO)3-komplexen und α-ferrocenyl-carbeniumionen mit nukleophilen

Tricarbonyl(fulvene)chromium complexes react with anionic nucleophiles to give functionally substituted cyclopentadienyl derivatives. The nucleophilic attack occurs at the exocyclic carbon atom of the fulvene ligand. Addition of PPh₂⁻ to (η⁶-6,6-dimethylfulvene)Cr(CO)₃ (1) yields the novel anion [(η⁵-C₅H₄C(CH₃)₂PPh₂)Cr-(CO)₃]⁻, which can be isolated as a K⁺, (C₂H₅)₄N⁺, (C₆H₅)₄P⁺, or Tl⁺ derivative (2–5). The potassium salt of the uncoordinated C₅H₄C(CH₃)₂PPh₂⁻ anion (7) is obtained by treatment of 6,6-dimethylfulvene with KPPh₂·2C₄H₈O₂. Similarly, NaC₅H₅ reacts with 1 to give Na[(η⁵-C₅H₄C(CH₃)₂C₅H₅)Cr(CO)₃] (8). The reactions of (6-dimethylaminofulvene)Cr(CO)₃ (15) with nucleophiles are accompanied by elimination of dimethylamine. Addition of Ph₃P=CH₂ to 15 gives an unstable product, but after reaction of 6-dimethylaminofulvene with Ph₃P=CH₂, the free ligand C₅H₄=CHCH=PPh₃ (17) can be isolated in moderate yields. Deeply colored anions of the type [(η⁵:η⁵-C₅H₄C(R)=C₅H₄)Cr₂(CO)₆]⁻ (R = H, N(CH₃)₂) are synthesized by reaction of 15 or (6-dimethylamino-6-methylthiofulvene)Cr(CO)₃ with NaC₅H₅ and subsequent complexation of the mononuclear intermediate with (CH₃CN)₃Cr(CO)₃. In addition, the synthesis of the new fulvene complexes [C₅H₄=CH(CH=CH)₂N(CH₃)Ph]M(CO)₃ (23, 24; M = Cr, Mo) is described. The investigation is extended to α-ferrocenylcarbenium ions, which are isoelectronic with (fulvene)Cr(CO)₃ complexes. [(η⁵-C₅H₅)Fe(C₅H₄CPh₂)]⁺ BF₄⁻ (25) adds tertiary phosphines at the exocyclic carbon atom to give phosphonium salts of the type [(η⁵-C₅H₅)Fe(C₅H₄CPh₂PR₃)]⁺BF₄⁻. A CO-substititution product of a tricarbonyl (fulvene)chromium complex is obtained for the first time by irradiation of (η⁶-6,6-diphenylfulvene)Cr(CO)₃ in the presence of PPh₃. In addition, an improved synthesis of the (CH₃CN)₃M(CO)₃ complexes (M = Cr, Mo, W) is reported.     

The tris(triphenylphosphine)osmium zerovalent complexes Os(CO)2(PPh3)3, .Os(CO)(CNR)(PPh3)3, Os(CO)(CS)(PPh3)3, Os(CS)(cNR)(PPh3)3 and derived compounds

Detailed procedures for the syntheses of Os(CO)₂(PPh₃)₃, Os(CO)(CNR)-(PPh₃)₃ (R = p-tolyl), Os(CO)(CS)(PPh₃)₃ and Os(CS)(CNR)(PPh₃)₃, together with the derived complexes Os(CO)₂(CS)(PPh₃)₂, Os(CO)(CS)(CNR)(PPh₃)₂, Os(η²-C₂H₄)(CO)(CNR)(PPh₃)₂, Os(η²-C₂H₄)(CO)(CS)(PPh₃)₂, Os(η²CS₂)(CO)₂-(PPh₃)₂, Os(η²CS₂)(CO)(CS)(PPh₃)₂, Os(η²-CS₂)(CO)(CNR)(PPh₃)₂, Os(η²PhC₂Ph)(CO)₂(PPh₃)₂ and OsH(C2Ph)(CO)₂(PPh₃)₂ are described.     

Coordination chemistry of the [Pt2(μ-S)2(PPh3)4] metalloligand with π-hydrocarbon derivatives of d ruthenium(II), osmium(II), rhodium(III) and iridium(III)

The reactivity of [Pt₂(μ-S)₂(PPh₃)₄] towards [RuCl₂(η⁶-arene)]₂ (arene=C₆H₆, C₆Me₆, p-MeC₆H₄Prⁱ=p-cymene), [OsCl₂(η⁶-p-cymene)]₂ and [MCl₂(η⁵-C₅Me₅)]₂ (M=Rh, Ir) have been probed using electrospray ionisation mass spectrometry. In all cases, dicationic products of the type [Pt₂(μ-S)₂(PPh₃)₄ML]²⁺ (L=π-hydrocarbon ligand) are observed, and a number of complexes have been prepared on the synthetic scale, isolated as their BPh₄⁻ or PF₆⁻ salts, and fully characterised. A single-crystal X-ray structure determination on the Ru p-cymene derivative confirms the presence of a pseudo-five-coordinate Ru centre. This resists addition of small donor ligands such as CO and pyridine. The reaction of [Pt₂(μ-S)₂(PPh₃)₄] with RuClCp(PPh₃)₂ (Cp=η⁵-C₅H₅) gives [Pt₂(μ-S)₂(PPh₃)₄RuCp]⁺. In addition, the reaction of [Pt₂(μ-S)₂(PPh₃)₄] with the related carbonyl complex [RuCl₂(CO)₃]₂, monitored by electrospray mass spectrometry, gives [Pt₂(μ-S)₂(PPh₃)₄Ru(CO)₃Cl]⁺.     

Synthesis and molecular structure of cisoid and transoid isomers of [Re2(CO)6(1,1′-bis(indenylidene)] derived from the reaction of [Re2(CO)8(MeCN)2] and diazoindene

The compound [Re₂(CO)₈(MeCN)₂] reacts with diazoindene (C₉H₆N₂) while refluxing in THF to afford three dirhenium products in which C₉H₆N₂ is cleaved with loss of N₂ and with incorporation of the residual indenylidene group into the products. Two indenylidene groups are coupled in two diastereomers of [Re₂(CO)₆(μ,η⁵:η⁵-1,1′-C₁₈H₁₂)] where C₁₈H₁₂=bis(indenylidene). X-ray structures show that these isomers are related as RR/SS and RS isomers. These have the two Re(CO)₃ groups coordinated transoid and cisoid, respectively to a trans bis(indenylidene) bridge. The third product is the μ-indenylidene complex [Re₂(CO)₈(μ,η¹:η⁵-C₉H₆)], which was also structurally characterised by X-ray diffraction.     

Synthesis and reaction chemistry of 4-nitrile-substituted NCN-pincer palladium(II) and platinum(II) complexes (NCN = [NC-4-C6H2(CH2NMe2)2-2,6])

Nitrile-functionalized NCN-pincer complexes of type [MBr(NC-4-C₆H₂(CH₂NMe₂)₂-2,6)] (6a, M = Pd; 6b, M = Pt) (NCN = [C₆H₂(CH₂NMe₂)₂-2,6]⁻) are accessible by the reaction of Br-1-NC-4-C₆H₂(CH₂NMe₂)₂-2,6 (2b) with [Pd₂(dba)₃ · CHCl₃] (5a) (dba = dibenzylidene acetone) and [Pt(tol-4)₂(SEt₂)]₂ (5b) (tol = tolyl), respectively. Complex 6b could successfully be converted to the linear coordination polymer {[Pt(NC-4-C₆H₂(CH₂NMe₂)₂-2,6)](ClO₄)}_n (8) upon its reaction with the organometallic heterobimetallic π-tweezer compound {[Ti](μ-σ,π-CCSiMe₃)₂}AgOClO₃ (7) ([Ti] = (η⁵-C₅H₄SiMe₃)₂Ti).The structures of 6a (M = Pd) and 6b (M = Pt) in the solid state are reported. In both complexes the d⁸-configurated transition metal ions palladium(II) and platinum(II) possess a somewhat distorted square-planar coordination sphere. Coordination number 4 at the group-10 metal atoms M is reached by the coordination of two ortho-substituents Me₂NCH₂, the NCN ipso-carbon atom and the bromide ligand. The NC group is para-positioned with respect to M.     

The designed synthesis and characterization of two novel heterometallic trinuclear incomplete cubane-like clusters [(CH3CH2)4N]{(M2CuS4)}(S2C2H4)2(PPh3) (M = Mo, W)

Two novel heterometallic trinuclear incomplete cubane-like clusters [(CH₃CH₂)₄N][{M₂CuS₄}(edt)₂(PPh₃)] (M = Mo, W) have been synthesized by reaction of [(CH₃CH₂)₄N]₂[M₂S₄(edt)₂] (M = Mo, W) with Cu(PPh₃)₂(dtp) [where edt is 1,2-ethane-dithiolato ligand, dtp is S₂P(OCH₂CH₃)₂⁻]. The two crystals are isomorphous in space group P1 (No. 1). The unit cell contains two independent molecules, but the two discrete anions have the same orientation for the PPh₃ ligands along one axis so the space group is undoubtedly non-centrosymmetric. The discrete anion contains two edt ligands and one PPh₃ ligand attached to one incomplete cubane-like cluster core {M₂CuS₄}³⁺ (M = Mo, W). The bond lengths of Mo---Mo[W---W] and the two Mo---Cu[W-Cu] are 2.852(2)[2.844(1)], 2.802(2)[2.765(3)], 2.760(2)[2.762(3)] Å, respectively. The M ₂S₄(edt)₂ (M = Mo, W) moiety remains almost unchanged, except that for the compound 1 the Mo=S double bond length elongates from av. 2.10 to av. 2.165 Å. The title clusters provide a new type of unsymmetric μ₂-bridging sulphido ligand. The incomplete cubane-like cluster core {Mo₂CuS₄}³⁺ of compound 1 is distorted because the two Cu---μ₂---S bond lengths are significantly different (2.313 Å and 2.409 Å), but the core {W₂CuS₄}³⁺ of compound 2 has approximately C_s symmetry. The IR spectra of the two title clusters and two starting materials are assigned.