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The two-step mechanochemical preparation of carbene-pyridine complexes of palladium and platinum is reported. The organometallic products, which represent a class of commercially available catalysts, are rapidly formed in excellent yield proving solvent-free synthesis to be a viable synthetic alternative even in the case of NHC-containing compounds.

para-Phenylenediamine (ppda) may be ground together with metal chloride salts MCl2 to produce the coordination network compounds [{(ppda)MCl2}n] {M = Zn (2), Cd (4), Cu (6)}. Its dihydrochloride salt [H2ppda]Cl2 can be ground with MCl2 to produce the layered salt structures [H2ppda][MCl4] {M = Zn (1), Cd (3), Cu (5)}, which (when M = Zn or Cd) may then be converted into 2 or 4 respectively by grinding with solid KOH. Alternatively, [H2ppda][MCl4] will react directly with appropriate basic metal compounds (hydroxides and/or carbonates) to give 2 or 4, which can then be converted back to the salts by reaction with gaseous HCl. The interconversion of 5 and 6 is more complicated, with different combinations of starting material giving different products. The crystal structure of 2 has been solved ab initio from the powder-diffraction data, and is shown to consist of zigzag polymeric chains containing alternating ppda and MCl2 units.

The d4 halide complexes [MX(CO)(η-RCCR)Tp′] {R = Me, M = W, X = F; R = Ph, M = Mo or W, X = F or Cl; Tp′ = hydrotris(3,5-dimethylpyrazolyl)borate} undergo two-electron oxidation in the presence of a halide source to give the d2 monocations [MX1X2(η-PhCCPh)Tp′]+ (R = Me, M = W, X1 = X2 = F; R = Ph, M = Mo, X1 = X2 = F or Cl; M = W, X1 = X2 = F or Cl; X1 = F, X2 = Cl). Each monocation (R = Ph) shows two reversible one-electron reductions (the second process was not detected for R = Me) corresponding to the stepwise formation of the neutral d3 and monoanionic d4 analogues, [MX1X2(η-PhCCPh)Tp′] and [MX1X2(η-PhCCPh)Tp′]− respectively; the potentials for the two processes can be ‘tuned’ over a range of ca. 1.0 V by varying M and X. Chemical one-electron reduction of [MX2(η-PhCCPh)Tp′]+ gave [MX2(η-PhCCPh)Tp′] (M = Mo or W, X = F or Cl). X-Ray structural studies on the redox pairs [WX2(η-PhCCPh)Tp′]z (X = F and Cl, z = 0 and 1+) show the alkyne to bisect the X–W–X angle in the d2 cations but align more closely with one M–X bond in the neutral d3 molecules, consistent with the anisotropic ESR spectra of the latter; the solution ESR spectrum of [MoF2(η-PhCCPh)Tp′] showed equivalent fluorine atoms, i.e the alkyne oscillates at room temperature. The successful isolation of [MX2(η-PhCCPh)Tp′]+ and [MX2(η-PhCCPh)Tp′] completes a series in which d6 to d2alkyne complexes are linked in a redox family tree by sequential one-electron transfer and substitution reactions. The implications for such trees in the production of new species and the selective synthesis of paramagnetic complexes acting as synthetically useful ‘alkyne radicals’ are discussed.

The d4 halide complexes [MX(CO)(η-RCCR)Tp′] {X = F, Cl, Br or I; R = Me or Ph; M = Mo or W; Tp′ = hydrotris(3,5-dimethylpyrazolyl)borate} undergo one-electron oxidation to the d3 monocations [MX(CO)(η-RCCR)Tp′]+, isolable for M = W, R = Me. X-Ray structural studies on the redox pairs [WX(CO)(η-MeCCMe)Tp′]z (X = Cl and Br, z = 0 and 1), the ESR spectra of the cations [WX(CO)(η-RCCR)Tp′]+ (X = F, Cl, Br or I; R = Me or Ph), and DFT calculations on [WX(CO)(η-MeCCMe)Tp′]z (X = F, Cl, Br and I; z = 0 and 1) are consistent with electron removal from a HOMO (of the d4 complexes) which is π-antibonding with respect to the W–X bond, π-bonding with respect to the W–C(O) bond, and δ-bonding with respect to the W–Calkyne bonds. The dependence of both oxidation potential and ν(CO) for [MX(CO)(η-RCCR)Tp′] shows an inverse halide order which is consistent with an ionic component to the M–X bond; the small size of fluorine and its closeness to the metal centre leads to the highest energy HOMO and the lowest oxidation potential. In the cations [MX(CO)(η-RCCR)Tp′]+ electronegativity effects become more important, leading to a conventional order for Cl, Br and I. However, high M–F π-donation is still facilitated by the short M–F distance.

The salts [NEt4][Ru(CN)(CO)2L(o-O2C6Cl4)] {L=PPh3 or P(OPh)3}, which undergo one-electron oxidation at the catecholate ligand to give neutral semiquinone complexes [Ru(CN)(CO)2L(o-O2C6Cl4)], react with the dimers [{Ru(CO)2L(micro-o-O2C6Cl4)}2] {L=PPh3 or P(OPh)3} to give [NEt4][(o-O2C6Cl4)L(OC)2Ru(micro-CN)Ru(CO)2L'(o-O2C6Cl4)] {L or L'=PPh3 or P(OPh)3}. The cyanide-bridged binuclear anions are, in turn, reversibly oxidised to isolable neutral and cationic complexes [(o-O2C6Cl4)L(OC)2Ru(micro-CN)Ru(CO)2L'(o-O2C6Cl4)] and [(o-O2C6Cl4)L(OC)2Ru(micro-CN)Ru(CO)2L'(o-O2C6Cl4)]+ which contain one and two semiquinone ligands respectively. Structural studies on the redox pair [(o-O2C6Cl4)(Ph3P)(OC)2Ru(micro-CN)Ru(CO)2(PPh3)(o-O2C6Cl4)]- and [(o-O2C6Cl4)(Ph3P)(OC)2Ru(micro-CN)Ru(CO)2(PPh3)(o-O2C6Cl4)] confirm that the C-bound Ru(CO)2(o-O2C6Cl4) fragment is oxidised first. Uniquely, [(o-O2C6Cl4){(PhO)3P}(OC)2Ru(micro-CN)Ru(CO)2(PPh3)(o-O2C6Cl4)]- is oxidised first at the N-bound fragment, indicating that it is possible to control the site of electron transfer by tuning the co-ligands. Crystallisation of [(o-O2C6Cl4)(Ph3P)(OC)2Ru(micro-CN)Ru(CO)2{P(OPh)3}(o-O2C6Cl4)] resulted in the formation of an isomer in which the P(OPh)3 ligand is cis to the cyanide bridge, contrasting with the trans arrangement of the X-Ru-L fragment in all other complexes of the type RuX(CO)2L(o-O2C6Cl4).

Reduction of [M(CO)2(η-RCCR′)Tp′]X {Tp′ = hydrotris(3,5-dimethylpyrazolyl)borate, M = Mo, X = [PF6]−, R = R′ = Ph, C6H4OMe-4 or Me; R = Ph, R′ = H; M = W, X = [BF4]−, R = R′ = Ph or Me; R = Ph, R′ = H} with [Co(η-C5H5)2] gave paramagnetic [M(CO)2(η-RCCR′)Tp′], characterised by IR and ESR spectroscopy. X-Ray structural studies on the redox pair [Mo(CO)2(η-PhCCPh)Tp′] and [Mo(CO)2(η-PhCCPh)Tp′][PF6] showed that oxidation is accompanied by a lengthening of the CC bond and shortening of the Mo–Calkyne bonds, consistent with removal of an electron from an orbital antibonding with respect to the Mo–alkyne bond, and with conversion of the alkyne from a three- to a four-electron donor. Reduction of [Mo(CO)(NCMe)(η-MeCCMe)Tp′][PF6] with [Co(η-C5H5)2] in CH2Cl2 gives [MoCl(CO)(η-MeCCMe)Tp′], via nitrile substitution in [Mo(CO)(NCMe)(η-MeCCMe)Tp′], whereas a similar reaction with [M(CO){P(OCH2)3CEt}(η-MeCCMe)Tp′]+ (M = Mo or W) gives the phosphite-containing radicals [M(CO){P(OCH2)3CEt}(η-MeCCMe)Tp′]. ESR spectroscopic studies and DFT calculations on [M(CO)L(η-MeCCMe)Tp′] {M = Mo or W, L = CO or P(OCH2)3CEt} show the SOMO of the neutral d5 species (the LUMO of the d4 cations) to be largely dyz in character although much more delocalised in the W complexes. Non-coincidence effects between the g and metal hyperfine matrices in the Mo spectra indicate hybridisation of the metal d-orbitals in the SOMO, consistent with a rotation of the coordinated alkyne about the M–C2 axis.

The radical cation [1,2-B2{1,2-(MeN)2C6H4}2]˙(+) has been synthesised and its structure and bonding have been probed using a combination of X-ray crystallography, EPR spectroscopy and DFT calculations which show that it represents a new type of radical centred primarily on two N-heterocyclic units joined by a B2 linker but with only a minor contribution from boron-based orbitals.

Cationic nitrile complexes and neutral halide and cyanide complexes, with the general formula [MnL1L2(NO)(eta-C5H4Me)]z, undergo one-electron oxidation at a Pt electrode in CH2Cl2. Linear plots of oxidation potential, Eo', vs. nu(NO) or the Lever parameters, EL, for L1 and L2, allow Eo' to be estimated for unknown analogues. In the presence of TlPF6, [MnIL'(NO)(eta-C5H4Me)] reacts with [Mn(CN)L(NO)(eta-C5H4Me)] to give [(eta5-C5H4Me)(ON)LMn(mu-CN)MnL'(NO)(eta5-C5H4Me)][PF6] which undergoes two reversible one-electron oxidations; DeltaE, the difference between the potentials for the two processes, differs significantly for stable cyanide-bridged linkage isomers. Novel pentametallic complexes such as [Mn[(mu-NC)Mn(CNBut)(NO)(eta5-C5H4Me)]4(OEt2)][PF6]2 and [Mn[(mu-NC)Mn(CNXyl)(NO)(eta5-C5H4Me)]4(NO3-O,O')][PF6], containing a trigonal bipyramidal and a distorted octahedral Mn(II) centre, respectively, result either from slow decomposition of the binuclear cyanide-bridged species or from the reaction of anhydrous MnI2 with four equivalents of [Mn(CN)L(NO)(eta5-C5H4Me)] in the presence of TlPF6.

The nominally square-planar coordination of the d8 complexes [MClL1L2(p-XC6H4NNNHC6H4X-p)] (M = Rh, L1 = L2 = CO, X = H, Me, Et or F; M = Ir, L1 = L2 = CO, X = Me; M = Pd or Pt, L1 = Cl, L2 = PPh3, X = Me; M = Pd, L1L2 = η3-C3H5, X = Me), with the triazene N-bonded via the imine group, is supplemented by an axial M⋯H–N interaction involving the terminal amino group.

The complex [Rh(CO)2{HC(pz′)3}][PF6], 1+[PF6]− {HC(pz′)3 = tris(3,5-dimethylpyrazolyl)methane}, prepared by reacting [{Rh(CO)2(μ-Cl)}2] with HC(pz′)3 in the presence of Tl[PF6], has a distorted square pyramidal structure with a κ3-HC(pz′)3 ligand. Carbonyl substitution with Lewis bases gives [Rh(CO)L{HC(pz′)3}][PF6] {L = PPh3, 2+[PF6]−; L = AsPh3, 3+[PF6]−; L = P(o-tolyl)3, 4+[PF6]−}, which have square planar κ2 structures, confirmed by X-ray crystallography for 2+[PF6]−. The cations 2+ and 3+ have the third pyrazolyl ring orientated pseudo-parallel to the square planar metal whereas 4+ more likely has the third ring orientated exo to that plane. One-electron oxidation of 2+ and 3+ gives the Rh(II) dications [Rh(CO)(PPh3){HC(pz′)3}]2+, 22+, and [Rh(CO)(AsPh3){HC(pz′)3}]2+, 32+, characterised by ESR spectroscopy. Complex 1+[PF6]−reacts with PhCCPh to give [Rh(CO)(η2-PhCCPh){HC(pz′)3}][PF6], 5+[PF6]−, in which the two-electron donor alkyne occupies an equatorial position in a trigonal bipyramidal κ3 structure. With MeCCR (R = Me or Et), 1+[PF6]− gives the κ2 square planar complexes [Rh{η4-C4Me2R2C(O)}{HC(pz′)3}][PF6] (R = Me, 6+[PF6]−; R = Et, 7+[PF6]−) in which the cyclopentadienone ligands are coordinated via two Rh–monoalkene bonds; the structurally characterised form of 7+ has the two alkyne units linked head-to-head with the CEt termini bound to the ketonic CO group. With HCCPh or HCCH, 1+ gives the octahedral, κ3 rhodium(III) metallacyclopentadienes [Rh(CO)(η1:η1′-CHCRCHCR){HC(pz′)3}][PF6] (R = Ph, 8+[PF6]−; R = H, 9+[PF6]−) with the two alkynes linked head-to-tail in 8+. The reaction of 1+ with HCCH also gives the cycloheptatrienone (tropone) derivative [Rh{η4-C6H6C(O)}{HC(pz′)3}][PF6], 10+[PF6]−, with a κ3 ligand and the cycloheptatrienone ligand bound to the metal via two Rh–C σ-bonds and one Rh–monoalkene interaction.

Dimethyltin dithiooxalate has been synthesised by the reaction of dimethyltin dichloride with potassium dithiooxalate. It may be used as a dithiooxalate (dto) transfer reagent, reacting with [PtL2Cl2] (L2 = 1,4-cyclooctadiene or 4,4′-bis(tert-butyl)-2,2′-bipyridine) to eliminate SnMe2Cl2 and form the corresponding platinum dithiooxalate compounds [Pt(COD)(dto)] 1 and [Pt(tBu2bipy)(dto)] 2. Reaction with the ruthenium compound [Ru(Me2bipy)(PPh3)2Cl2] 3 (Me2bipy = 4,4′-dimethyl-2,2′-bipyridine) does not proceed analogously however, eliminating from the ruthenium one chloride and one triphenylphosphine ligand, and thus producing not SnMe2Cl2 but “[SnMe2Cl]+”. This moiety becomes chelated within the dithiooxalate to produce the new ‘Coucouvanis’ type compound [cis-Ru(Me2bipy)(PPh3)Cl(μ-dto)(SnMe2Cl)] 4. Reaction of 4 with DMSO causes the elimination of SnMe2Cl2 by abstracting the tin centre and the second chloride ligand, producing cis-[Ru(Me2bipy)(PPh3)(DMSO)(dto)] 5. Upon treating 3 with [p-NNC6H4F][BF4] the oxidation product [Ru(Me2bipy)(PPh3)2Cl2][BF4] 6 is formed. 6 reacts with SnMe2(dto) to produce a second bimetallic complex, [Ru(Me2bipy)(PPh3)2(μ-dto)(SnMe2Cl)][BF4] 7a. The nature of the reduction products of 4 and 7 is explored, and the X-ray crystal structures of 2 and 5 are presented.

X-Ray structural studies on the redox pair [Cr(CO)2(η-PhCCPh)(η-C6Me5H)]z (z = 0 and 1) show that one-electron oxidation of the neutral complex results in a shortening of the Cr–Calkyne bonds and a lengthening of the Cr–C(O) bonds, consistent with depopulation of a HOMO antibonding with respect to the metal–alkyne interaction. Oxidation leads to an increase in the substitutional lability of the Cr–CO bonds so that [Cr(CO)2(η-RCCR)(η-C6Me6)]+ (R = Ph or C6H4OMe-p) reacts with Lewis bases to give [Cr(CO)L(η-RCCR)(η-C6Me6)]+ {L = CNXyl, P(OMe)3 and P(OCH2)3CEt}, X-ray studies on which show a rotation of the alkyne to align with the remaining Cr–CO bond. ESR spectroscopic studies on [Cr(CO)L(η-RCCR)(η-C6Me6)]+ show delocalisation of the unpaired electron onto the alkyne ligand, consistent with its description as a three-electron donor. The cations [Cr(CO)L(η-RCCR)(η-C6Me6)]+ undergo both one-electron reduction and oxidation, and chemical oxidation of [Cr(CO){P(OCH2)3CEt}(η-p-MeOC6H4CCC6H4OMe-p)(η-C6Me6)]+ with AgPF6 gives the dication [Cr(CO){P(OCH2)3CEt}(η-p-MeOC6H4CCC6H4OMe-p)(η-C6Me6)]2+. Thus the two-electron alkyne of [Cr(CO)2(η-RCCR)(η-C6Me6)] is converted into the four-electron alkyne of [Cr(CO)L(η-RCCR)(η-C6Me6)]2+ by an ECE (E = electrochemical, C = chemical) process in which all of the intermediates have been fully characterised.

The complex [Mo(CO)(PhCCPh)2(η-C5Me5)][BF4] reacted with three equivalents of 2,6-dimethylphenyl isocyanide, CNxyl, to give the tris(isocyanide) complex [Mo(PhCCPh)(CNxyl)3(η-C5Me5)][BF4] 1. With four equivalents of CNxyl, alkyne–isocyanide coupling leads to the formation of the diiminometallacyclopentene [Mo{C(Nxyl)C(Ph)C(Ph)CNxyl}(CNxyl)2(η-C5Me5)][BF4] 2 which decomposes in thf at room temperature to give the tetrakis(isocyanide) complex [Mo(CNxyl)4(η-C5Me5)][BF4] 3. In dichloromethane, 2 gives the diiminocyclobutene xylNCC(Ph)C(Ph)CNxyl 4, the η2-iminoacyl complex [MoCl(CNxyl)2(η2-xylNCCH2Cl)(η-C5Me5)][BF4] 5, formed by an addition reaction with dichloromethane, and the metallacyclobutene complex [Mo{C(Ph)C(Ph)CN(H)xyl}(CNxyl)3(η-C5Me5)][BF4]26. Complex 5 is more efficiently synthesized by photolysis of 3 in dichloromethane, but the same reaction in chloroform produces the dichloromethyl complex [MoCl(CHCl2)(CNxyl)3(η-C5Me5)][BF4] 7 which thermally decomposes to [MoCl2(CNxyl)3(η-C5Me5)][BF4] 8. Reaction of 2 with HCl in diethyl ether results in protonation of the metallacyclic ring and formation of the iminium metallacyclopentene [MoCl{C(Nxyl)C(Ph)C(Ph)CN(H)xyl}(CNxyl)2(η-C5Me5)][BF4] 9. Compound 3 is oxidised by AgBF4 to give the molybdenum(IV) complex [MoF(CNxyl)4(η-C5Me5)][BF4]210. The molecular structures of 3–6, 7/8 and 10 have been determined by X-ray crystallography.

The novel compound 2-cyanaminofluoren-9-one (HL) has been synthesized, and is readily deprotonated to form the corresponding cyanamide anion L–. This has been isolated as the Tl+L– and AsPh4+L– salts. The UV/visible spectra of HL and AsPh4+L– show the same amine to carbonyl charge transfer transition seen in other aminofluorenones, although at longer wavelengths. The compound AsPh4+L– undergoes the reversible one electron reduction typical of fluorenones, whilst HL undergoes an irreversible reduction. The crystal structure of AsPh4+L– was determined and related to the solvatochromic behaviour of the L– anion. Some simple EHMO calculations have been carried out on the L– anion of AsPh4+L–, which show the cyanamide based HOMO and carbonyl based LUMO involved in the aforementioned CT transition. The thallium salt Tl+L– has also been used as a transmetallating agent in reaction with trimethyltin chloride to produce the corresponding tin cyanamide complex [SnMe3L], and in reaction with (triphenylphosphine)gold chloride to produce the first reported gold cyanamide compound [AuL(PPh3)], whose crystal structure has been determined.

Reaction of the dicarbon-containing complex [Ru5(µ5-C2)(µ-SMe)2(µ-PPh2)2(CO)11] 1 with monosubstituted alkynes HCCR (R = Ph, But or SiMe3) yielded [Ru5(µ5-CCCHCR)(µ-SMe)2(µ-PPh2)2(CO)10] (R = Ph, But or SiMe3) in which the Ru5 pentagon in 1 is retained. Coupling of the C2 and alkyne moieties forms a CCCHCR ligand which in combination with one Ru atom forms a metallacycle. The unsubstituted terminal carbon has a strong carbidic interaction with four of the Ru atoms. Carbonylation of the R = Ph and SiMe3 complexes yields [Ru5(µ5-CCCHCR)(µ-SMe)2(µ-PPh2)2(CO)11] (R = Ph or SiMe3), in which one Ru atom has been extruded from the cluster, although retained by co-ordination to bridging PPh2, SMe and hydrocarbon ligands. A minor product in each case was identified as [Ru5{µ5-CC[C(O)SMe]CHCR}(µ-SMe)(µ-PPh2)2(CO)10 (R = Ph or SiMe3). Here, the organic ligand is formed by combination of the CCCHCR ligand with CO and one of the SMe groups and is attached to an Ru5 core with an open-envelope conformation. Pyrolysis of [Ru5(µ-CCCHCR)(µ-SMe)2(µ-PPh2)2(CO)11] afforded [Ru5(µ5-CCCHCR)(µ-SMe)2(µ-PPh2)2(CO)10] and [Ru5(µ5-CCCHCR)(µ3-SMe)(µ-SMe)(µ-PPh2)2(CO)9] (R = Ph or SiMe3), in which one SMe group becomes triply bridging. The complex [Ru5{µ5-CC(CHCSiMe3)C(=CHSiMe3)CO}(µ-SMe)2(µ-PPh2)2(CO)8], in which the organic ligand, formed by combination of CO, HC2SiMe3 and CCHSiMe3 molecules, is attached to the opposite side of the open-envelope cluster from that in [Ru5{µ5-CC[C(O)SMe]CHCR}(µ-SMe)(µ-PPh2)2(CO)10], has also been isolated. The structures of five complexes were determined from single-crystal X-ray studies.

Reaction of the dicarbon-containing complex Ru5(µ5-C2)(µ-SMe)2(µ-PPh2)2(CO)11 1 with diphenylethyne gave as major products Ru5(µ5-CCCPhCPh)(µ-SMe)2(µ-PPh2)2(CO)10 2 and Ru5(µ5-CCPhCPh)(µ3-SMe)(µ-SMe)(µ-PPh2)2(CO)9 3. The only product from the reaction between 1 and but-2-yne was identified as Ru5(µ5-CCCMeCMe)(µ3-SMe)(µ-SMe)(µ-PPh2)2(CO)9 4. Pyrolysis of 2 gave 3. Carbonylation of 3 yields the complex Ru5(CCCPhCPh)(µ-SMe)2(µ-PPh2)2(CO)11 5, further heating of which regenerated a mixture of 2 and 3. The structures of 2 and 3 were determined from single crystal X-ray studies. The Ru5 clusters in both complexes adopt the open-envelope conformation, the Ru4 rhombus being planar in 2, but bent across the Ru(3)· · ·Ru(5) diagonal by 39.6° in 3. The organic ligand is formed by coupling of the C2 group in 1 with the alkyne and is attached by three of the four carbons in 2 and by all four in 3, atom C(1) being strongly attached to the Ru4 rhombus. In 3, atoms C(1,2,3,4) have an η4 interaction with Ru(4).

The reaction between [Ru 5 (µ 5 -C 2 )(µ-SMe) 2 ( µ-PPh 2 ) 2 (CO) 11 ] 1 and CO (30 atm) yielded [Ru 5 (µ 4 -C 2 )(µ-SMe) 2 ( µ-PPh 2 ) 2 (CO) 13 ] 2 and [Ru 4 (µ 4 -C 2 )(µ-SMe) 2 ( µ-PPh 2 ) 2 (CO) 10 ] 3, both characterised by single-crystal X-ray crystallography. In 2, addition of 2CO results in the net cleavage of two Ru–Ru bonds and expansion of the resulting Ru 3 cluster. The C 2 ligand bridges one edge of the Ru 3 core and the isolated Ru–Ru bonded fragment in a µ,µ-η 1 ,η 2 mode, albeit with asymmetric Ru–C 2 π interactions. In 3, one Ru atom has been excised from the cluster present in 1. One Ru–Ru bond is bridged by two SMe groups as a result of migration of one of these. Although the C 2 ligand bridges all four metal atoms, only two Ru – Ru bonds are present, with the non-bonded Ru · · · Ru vector being bridged by PPh 2 . Extended-Huckel molecular orbital calculations have been used to rationalise the observed structures.

The reaction between [Ru 5 (µ 5 -C 2 PPh 2 )(µ- PPh 2 )(CO) 13 ] and Me 2 S 2 yielded [Ru 5 (µ 5 -C 2 PPh 2 )(µ- SMe) 2 (µ-PPh 2 )(CO) 13 ] as the major product. When heated the latter yielded the dicarbon complexes [Ru 5 (µ 5 -C 2 )(µ-SMe) 2 ( µ-PPh 2 ) 2 (CO) 12 ] and [Ru 5 (µ 5 -C 2 )(µ-SMe) 2 ( µ-PPh 2 ) 2 (CO) 11 ]. In large-scale preparations of the latter four minor products were isolated: two isomers of [Ru 5 (µ 5 -C 2 PPh 2 )(µ- SMe) 2 (µ-PPh 2 )(CO) 12 ], the tetranuclear complex [Ru 4 (µ 4 -C 2 PPh 2 )(µ- SMe) 2 (µ-PPh 2 )(CO) 10 ] and [Ru 5 (µ 5 -C 2 )(µ-SMe) 4 ( µ-PPh 2 ) 2 (CO) 10 ]. The latter is also formed by direct reaction of [Ru 5 (µ 5 -C 2 )(µ-SMe) 2 ( µ-PPh 2 ) 2 (CO) 11 ] with Me 2 S 2 . All new complexes have been fully characterised by single-crystal X-ray studies. In the three Ru 5 (C 2 PPh 2 ) complexes the C 2 PPh 2 ligand acts as a seven-electron donor, whereas in the Ru 4 complex it donates only five electrons to the cluster. In the C 2 complexes, the different C–C separations [between 1.26(2) and 1.305(5) A] suggest a variable degree of interaction with the metal core (electron donation and back-bonding), the ligand formally donating either six or four electrons to the cluster. This is borne out by the Ru–Ru separations, average values of which range between 2.791 and 2.916 A. The conversion of [Ru 5 (µ 5 -C 2 PPh 2 )(µ- PPh 2 )(CO) 13 ] into [Ru 5 (µ 5 -C 2 )(µ-SMe) 2 ( µ-PPh 2 ) 2 (CO) 11 ] involves sequential formation of several of these complexes, which reactions are discussed.

Reactions of [Co2(CO)8] with [{Mn(CO)11}2(µ-bdpp)][Mn Ru3, Os3, Re3(µ-H)3 or Ru4(µ-H)4; bdpp PPh2C2C2PPh2] afforded [{Mn(CO)11}2{µ-PPh2[C2Co2(CO)6]C2 PPh2}][Mn Ru31, Os32, Re3(µ-H)33 or Ru4(µ-H)44] in which the Co2(CO)6 moiety bonds to one of the CC triple bonds of the bridging bdpp ligand. Pyrolysis of 1 yielded [{Ru3(CO)11}{µ-PPh2[C2Co2(CO)6]C2}{Ru2(µ-PPh2)(CO)6}]5, which is formed by concomitant addition of a P–C(sp) bond to one Ru3 cluster and elimination of a Ru(CO)4 fragment. In [{Os3(CO)11}(µ-PPh2C2C2){Co2Os3(µ-PPh2)(CO)13}]8, obtained by heating 2, the Co2Os3 cluster consists of three edge-sharing triangles; the C2 fragment interacts with all five metal atoms. Reaction of the mixed-metal complex [{Os3(CO)11}(µ-bdpp){Re3(µ-H)3(CO)11}]10 with [Co2(CO)8] yielded a 1:1 isomeric mixture of [{Os3(CO)11}{µ-PPh2[C2Co2(CO)6]C2PPh2}{Re3(µ-H)3(CO)11}]11a and [{Re3(µ-H)3(CO)11}{µ-PPh2[C2Co2(CO)6]C2PPh2}{Os3(CO)11}]11b. Pyrolysis of 11a afforded [Co2Os3Re{µ6-C2CCH(PPh 2)}(µ-PPh2)(µ-CO)2(CO)14]12 in which all three transition metals form a cluster about the C4P fragment of the original bdpp ligand, which has also added one H atom to the carbon adjacent to the PPh2 group. The second PPh2 group bridges an Os–Os bond. Molecular structures of 5, 8 and 12 were determined by X-ray crystallography.

Reaction of the labile triosmium cluster [Os3(CO)10(NCMe)2] with the thienyl substituted diyne [(C4H3S)C2C2(C4H3S)] affords [Os3(CO)10{μ3-η2-(C4H3S)C2C2(C4H3S)}] 1 and the novel co-linear cluster [Os3(CO)11{μ3-η4-(C4H3S)C2C2(C4H3S)}] 2 in reasonable yield; the X-ray structure of 2 shows that the diyne is coordinated to an ‘open’ triosmium unit as a 1,2,3-triene-1,4-diyl unit with essentially equal CC bond distances.

Kara, Hülya (Balikesir Author), A series of crystalline salts based on the complex dianion [Fe(dto)(2)(NO)](2-) (dto = 1,2-dithiooxalate) with hydrogen-bond donor cations have been synthesised. The preparation and structural characterisation of the new crystalline phases [4,4'-H(2)bipy][Fe(dto)(2)(NO)]center dot H2O (1), [3,3'-H(2)bipy][Fe (dto)(2)(NO)] (2) and [H(2)Me(4)bipyz][Fe(dto)(2)(NO)]center dot 2H(2)O (3) (Me(4)bipyz = 3,3',5,5'-tetramethyl-4,4'-bipyrazole) are reported, and show that a charge-assisted NH center dot center dot center dot dto synthon is formed in each of compounds 1-3. In compound 1 the anion forms a dimer in the solid-state, and variable temperature magnetic susceptibility measurements reveal a weak antiferromagnetic interaction with a best fit superexchange parameter J = -3.18 (2) cm(-1), where H = -2JS(1)S(2)., TUBITAK TBAG - 108T431 Royal Society EPSRC University of Bristol

A number of different compounds have been synthesised by reaction of solutions containing Fe(NCE)2 (E = S, Se) with solutions containing 3,3′-bipyridine. When the solvent used is methanol, the products are the monomeric compounds trans-{Fe(NCS)2(3,3′-bipy)2(MeOH)2} 1 or trans-{Fe(NCSe)2(3,3′-bipy)2(MeOH)2} 2, but when acetonitrile is used the layered coordination network {Fe(NCS)2(3,3′-bipy)2} 3 or doubly interpenetrated coordination network {Fe(NCSe)2(3,3′-bipy)2} 4 is formed instead. Using methanol to dissolve the Fe(NCE)2 and CHX3 (X = Cl, Br) to dissolve the 3,3′-bipyridine yields solvated coordination networks of stoichiometry {Fe(NCE)2(3,3′-bipy)2}·2CHX3. The crystal structures of all of these compounds except 4 are presented.

The d2/d3 redox pair [WF2(PhCCPh)Tp′]z [z = +1 or 0, Tp′ = hydrotris(3,5-dimethylpyrazolyl)borate] is the missing link in a ‘redox family tree’ relating the d6 tricarbonyls [M(CO)3L]− to the d2 trihalides [MX3L] (M = Mo or W, L = Cp or Tp′) by a series of stepwise reactions involving sequential one-electron oxidation followed by ligand substitution.

Variable temperature NMR and EPR spectroscopic studies provide rates and activation parameters for alkyne rotation and oscillation, respectively, in the fluxional redox pair [Mo{P(OMe)3}2(MeCCMe)Cp][BF4] (diamagnetic) and [Mo{P(OMe)3}2(MeCCMe)Cp] (paramagnetic).

The crystal structures of eight solvates of {Fe(4,4′-bipyridine)2(NCS)2}n have been determined. All of them contain a layered iron–bipyridine–thiocyanate framework formed from approximately square infinite two-dimensional (4,4) iron–bipyridine grids, with the solvent molecules hosted between adjacent layers. All the structures contain the iron(II) centres in the high-spin electronic configuration, and magnetic susceptibility measurements on the toluene and nitrobenzene solvates do not reveal any spin-crossover behaviour.

[{(4,4′-bipy)ZnCl2}n] (4) is known in three different polymorphs, in the space groups C2/c (4a), Pnma (4b) and Pban (4c). Solution synthesis produces a mixture of 4a and 4b, but solid-state synthesis, either by grinding together 4,4′-bipy and ZnCl2 or by heating [4,4′-H2bipy][ZnCl4] 3 to thermally eliminate HCl, generates only the 4b form, demonstrating that solid-state synthesis can exert control over polymorph formation; other solid-state preparations of 4 such as reaction of basic zinc carbonate with [4,4′-H2bipy]Cl2 or reaction of [4,4′-H2bipy][ZnCl4] 3 with KOH also increase the amount of 4b generated relative to the solution synthesis. It is also possible to form the mixed-metal phases [{(4,4′-bipy)Co1−xZnxCl2}n] 4x as effectively homogeneous solid-solutions by the same techniques, and when x 0.5, the amount of this polymorph is still greater than would be expected for a predominantly zinc-containing phase.

Solid pyrazole reacts with HCl gas to form pyrazolium chloride [H2pz]Cl, which reacts in the solid state, under grinding, with metal chlorides MCl2 (M = Co, Zn, Cu) to form the pyrazolium tetrachlorometallate salts [H2pz]2[MCl4] (M = Co 1, Zn 3, Cu 5). Salt 5 cannot be made in solution, and upon standing at room temperature spontaneously emits HCl to give the coordination compound [CuCl2(Hpz)2] (6). Compounds 1 and 3 do not exhibit this behaviour, but can be ground together with bases such as KOH or K2CO3 to effect the elimination of HCl and afford their respective [MCl2(Hpz)2] compounds (M = Co 2, Zn 4). 2, 4 and 6 can also be synthesised in the solid-state by direct reaction of the appropriate metal chloride with pyrazole, or by reaction of a basic metal salt such as the carbonate or hydroxide with pyrazolium chloride. 4 and 6 {and their nickel analogue [NiCl2(Hpz)2]} can be ground with a further two equivalents of base to make the known polymeric metal pyrazolates [M(pz)2]n (M = Ni 7, Cu 8, Zn 9); the same reaction appears to work for the cobalt analogue 2, but the presumed product [Co(pz)2]n10 then decomposes by oxidation. The imidazolate complexes [M(im)2] (M = Ni, 11; Cu, 12; Zn, 13; Co, 14) were similarly prepared by grinding the appropriate [M(Him)2Cl2] precursor with KOH.

The persistent radical, [BCl(2)(bipy)](*) (bipy = 2,2'-bipyridyl), has been prepared and characterised by X-ray crystallography, ESR and DFT calculations. The structure is compared with that of the cation, [BCl(2)(bipy)](+).

The cyclic voltammograms of the alkyne complexes [M(SR)L(η-R′CCR′)(η-C5H5)] (M = Mo or W, R = Me or Ph, R′ = Me or Ph) show two oxidation processes. Both are irreversible for the stereochemically rigid carbonyls (L = CO) but the first is reversible for the fluxional phosphites {L = P(OMe)3}; the paramagnetic monocations [M(SPh){P(OMe)3}(η-MeCCMe)(η-C5H5)]+ were detected by ESR spectroscopy after in situ chemical one-electron oxidation. By contrast, the hydrotris(pyrazolyl)borate analogues [W(SR)(CO)(η-PhCCPh)Tp′] {R = Me or Ph, Tp′ = hydrotris(3,5-dimethylpyrazolyl)borate} are oxidised in two reversible steps to the corresponding mono- and dications; the redox pair [W(SPh)(CO)(η-PhCCPh)Tp′]z (z = 0 and 1+) has been structurally characterised. A comparison of the redox potentials for the oxidation of [W(SR)(CO)(η-PhCCPh)Tp′] with those of the halide analogues [WX(CO)(η-PhCCPh)Tp′] suggests that the factors which give rise to the inverse halide order for the latter may not operate for the thiolates, which appear to be the better π-donors in all three redox states [WL(CO)(η-PhCCPh)Tp′]z (L = halide or thiolate, z = 0, 1+ and 2+).

The complexes [(η-C5Me5)(ON)LMn(μ-CN)M(CO)(RCCR)Tp′]+ (L = CNXyl, M = Mo; L = CNBut, M = Mo or W, R = Ph or Me) and trans- or cis-[(dppm){(EtO)3P}(OC)2Mn(μ-CN)M(CO)(PhCCPh)Tp′]+, and their linkage isomers [(η-C5Me5)(ON)LMn(μ-NC)M(CO)(PhCCPh)Tp′]+ and trans- or cis-[(dppm){(EtO)3P}(OC)2Mn(μ-NC)M(CO)(PhCCPh)Tp′]+, undergo two one-electron oxidations. The complexes [(η-C5Me5)(ON)LMn(μ-XY)M(CO)(RCCR)Tp′]+ (XY = CN or NC) are oxidised first at the N-bound metal centre and then at the C-bound centre. For [(dppm){(EtO)3P}(OC)2Mn(μ-XY)M(CO)(PhCCPh)Tp′]+, the trans isomers are first oxidised at manganese whereas the cis isomers are first oxidised at M. Thus, the order of one-electron oxidation of the two series of binuclear monocations is influenced by linkage isomerisation of the cyanide bridge and cis-trans isomerisation of the Mn(CO)2 group. IR spectroscopic changes on reaction of Ag+ with [(η-C5Me5)(ON)(ButNC)Mn(μ-CN)W(CO)(MeCCMe)Tp′]+ are consistent with one-electron at the N-bound tungsten centre. Likewise, trans-[(dppm){(EtO)3P}(OC)2Mn(μ-NC)M(CO)(PhCCPh)Tp′]+ (M = Mo or W) give the stable dications [(dppm){(EtO)3P}(OC)2Mn(μ-NC)M(CO)(PhCCPh)Tp′]2+. Significantly longer Mn-P bond distances in trans-[(dppm){(EtO)3P}(OC)2Mn(μ-NC)Mo(CO)(PhCCPh)Tp′]2+ than in trans-[(dppm){(EtO)3P}(OC)2Mn(μ-NC)Mo(CO)(PhCCPh)Tp′]+ are consistent with one-electron oxidation first at Mn(I); the alignment of the (CN)Mn(CO)2{P(OEt)3}(dppm) fragment relative to the alkyne in trans-[(dppm){(EtO)3P}(OC)2Mn(μ-NC)Mo(CO)(PhCCPh)Tp′]+ suggests it acts as a π-acceptor, in contrast to related species such as trans-(NC)Mn(CO)2{P(OEt)3}(dppm) and (NC)Mn(NO){P(OPh)3}(π-C5H4Me) which behave as simple N-donors.

The reaction of a mixture of the sodium salts of dihydrobis(4-ethyl-3-methyl-5-thioxo-1,2,4-triazolyl)borate, NaBt, and hydrotris(4-ethyl-3-methyl-5-thioxo-1,2,4-triazolyl)borate, NaTt, with [{Rh(cod)(mu-Cl)}2] gave [Rh(cod)Bt] and [Rh(cod)Tt], which separately react with CO gas to give the unstable dicarbonyl [Rh(CO)2Bt] and an equilibrium mixture of two isomers of [Rh(CO)2Tt] and [(RhTt)2(mu-CO)3], respectively. Tertiary phosphorus donor ligands react with the mixture of [Rh(CO)2Tt] and [(RhTt)2(mu-CO)3] to give [Rh(CO)(PR3)Tt] (R = Cy, NMe(2), Ph or OPh) and [Rh{P(OPh)3}2Tt] in which rhodium is bound to two sulfur atoms of the scorpionate ligand; the B-H bond is directed towards the metal to give an agostic-like B-H...Rh interaction. Dinuclear [(RhTt)2(mu-CO)3] has kappa3[S3]-bound Tt ligands with a rhodium-rhodium bond bridged by three carbonyls. In solution the mononuclear Tt complexes undergo rapid dynamic interchange of the three thioxotriazolyl rings, probably via kappa3[S3]-coordinated intermediates. The monocarbonyls [Rh(CO)(PR3)Tt] (R = Cy, NMe2 or Ph) react with two equivalents of [Fe(eta-C5H5)2][PF6] in the presence of triethylamine to give the monocationic rhodaboratranes [Rh(CO)(PR3){B(taz)3}]+, with boron NMR spectroscopy providing evidence for the boron-rhodium bond. In the solid state, rhodium is bound to the three sulfur atoms and the boron of the B(taz)3 fragment, forming a tricyclo[3.3.3.0] cage. The phosphine is trans to the Rh-B bond, the long Rh-P bond indicating a pronounced trans influence for the coordinated boron. The cation [Rh(CO)(PPh3){B(taz)3}]+ reacts with [NBu(n)(4)]I to give [Rh(PPh3)I{B(taz)3}], in which the halide is trans to the Rh-B bond, and a second species, possibly [Rh(CO)I{B(taz)3}]. The dirhodaboratrane [Rh2(PCy3){B(taz)3}2][PF6]2, a minor byproduct in the synthesis of [Rh(CO)(PCy3){B(taz)3}][PF6], has a distorted square pyramidal rhodium atom with a vacant site trans to the Rh-B bond. The second metal has four coordination sites filled by the sulfur and boron atoms of a second B(taz)3 unit, the remaining octahedral sites occupied by two of the sulfur atoms of the first B(taz)3 unit which therefore bridges the two rhodium atoms.

The preparation of the complex salts [H2im]2[MCl4] (H2im = imidazolium, M = Co, 1; Zn, 2; Cu, 3) and coordination compounds [MCl2(Him)2] (M = Co, 4; Zn, 5; Cu, 6) by a range of solid-state and solid-gas reactions is reported. Compounds 4–6 and the related [{MCl2(4,4′-bipy)}n] (M = Co, 7; Zn, 8) were prepared by the solid state reactions of metal hydroxide or carbonate salts (or their equivalent) with the hydrochloride salt of the appropriate ligand (imidazole or 4,4′-bipy).

The new square-planar platinum–diimine–dithiolate compounds [Pt(mesBIAN)SS] have been synthesised {mesBIAN = bis(mesityl)biazanaphthenequinone; SS = 1,2-dithiooxalate (dto) 1, maleonitriledithiolate (mnt) 2, 1,2-benzenedithiolate (bdt) 3, 3,4-toluenedithiolate (tdt) 4 and 1,3-dithia-2-thione-4,5-dithiolate (dmit) 5}, and the X-ray crystal structures of 3 and 5 determined. Cyclic voltammetry reveals that all the compounds form stable anions, and ESR spectroscopy of these anions shows that the SOMO is based upon the mesBIAN ligand; compounds 2–5 also show a reversible oxidation wave in their CV. Computational studies reveal that charge-transfer processes from orbitals that are combinations of metal and dithiolate ligand to a mesBIAN π*-based LUMO are responsible for the low energy absorptions seen in the UV/visible spectra of these compounds, and that the reverse process is responsible for the observed room-temperature solution luminescence of [Pt(mesBIAN)Cl2] and 1, 2 and 5. Compounds 3 and 4, containing aromatic thiolates, were not found to luminesce under the same conditions. Resonance Raman experiments have shown the origin of band-broadening of the lowest-energy absorption band in the absorption spectra of 2–5 to be due to vibronic structure within one electronic transition.

The reaction of [Mn(CN)L'(NO)(eta(5)-C(5)R(4)Me)] with cis- or trans-[MnBrL(CO)(2)(dppm)], in the presence of Tl[PF(6)], gives homobinuclear cyanomanganese(i) complexes cis- or trans-[(dppm)(CO)(2)LMn(micro-NC)MnL'(NO)(eta(5)-C(5)R(4)Me)](+), linkage isomers of which, cis- or trans-[(dppm)(CO)(2)LMn(micro-CN)MnL'(NO)(eta(5)-C(5)R(4)Me)](+), are synthesised by reacting cis- or trans-[Mn(CN)L(CO)(2)(dppm)] with [MnIL'(NO)(eta(5)-C(5)R(4)Me)] in the presence of Tl[PF(6)]. X-Ray structural studies on the isomers trans-[(dppm)(CO)(2){(EtO)(3)P}Mn(micro-NC)Mn(CNBu(t))(NO)(eta(5)-C(5)H(4)Me)](+) and trans-[(dppm)(CO)(2){(EtO)(3)P}Mn(micro-CN)Mn(CNBu(t))(NO)(eta(5)-C(5)H(4)Me)](+) show nearly identical molecular structures whereas cis-[(dppm)(CO)(2){(PhO)(3)P}Mn(micro-NC)Mn{P(OPh)(3)}(NO)(eta(5)-C(5)H(4)Me)](+) and cis-[(dppm)(CO)(2){(PhO)(3)P}Mn(micro-CN)Mn{P(OPh)(3)}(NO)(eta(5)-C(5)H(4)Me)](+) differ, effectively in the N- and C-coordination respectively of two different optical isomers of the pseudo-tetrahedral units (NC)Mn{P(OPh)(3)}(NO)(eta(5)-C(5)H(4)Me) and (CN)Mn{P(OPh)(3)}(NO)(eta(5)-C(5)H(4)Me) to the octahedral manganese centre. Electrochemical and spectroscopic studies on [(dppm)(CO)(2)LMn(micro-XY)MnL'(NO)(eta(5)-C(5)R(4)Me)](+) show that systematic variation of the ligands L and L', of the cyclopentadienyl ring substituents R, and of the micro-CN orientation (XY = CN or NC) allows control of the order of oxidation of the two metal centres and hence the direction and energy of metal-metal charge-transfer (MMCT) through the cyanide bridge in the mixed-valence dications. Chemical one-electron oxidation of cis- or trans-[(dppm)(CO)(2)LMn(micro-NC)MnL'(NO)(eta(5)-C(5)R(4)Me)](+) with [NO][PF(6)] gives the mixed-valence dications trans-[(dppm)(CO)(2)LMn(II)(micro-NC)Mn(I)L'(NO)(eta(5)-C(5)R(4)Me)](2+) which show solvatochromic absorptions in the electronic spectrum, assigned to optically induced Mn(I)-to-Mn(II) electron transfer via the cyanide bridge.

Friedel–Crafts reactions in the ionic liquid system 1-methyl-3-ethylimidazolium chloride–aluminium(III) chloride can be performed with excellent yields and selectivities, and in the case of anthracene, have been found to be reversible.

A series of salts of pyridinium boronic acids: [HNC5H4B(OH)2-4]2[M(S2C2O2)2]·2H2O (M = Cu 1, Ni 2, Pd 3, Pt 4), [HNC5H4B(OH)2-4]2[Pt(O2C2O2)2] (5); [HNC5H4B(OH)2-3]2 [M(S2C2O2)2] (M = Cu 6, Ni 7, Pd 8, Pt 9) and [HNC5H4B(OH)2-3]2[Pt(O2C2O2)2] (10) have been prepared and characterized by X-ray diffraction methods. Salts 2, 3 and 4 are isostructural and isomorphous and contain hydrogen-bonded supermolecules of form [pyridinium]2[M(S2C2O2)2] linked by BOH⋯OB and B(OH)–water hydrogen bonds into a three-dimensional network. Anhydrous salt 5 has a different structure in which the ions are linked by R(2,2)8 B(OH)2⋯carboxylate and pyridinium⋯carboxylate interactions to form a planar hydrogen-bonded ribbon. Salts 6, 7, 8 and 10 are all isostructural and isomorphous and contain hydrogen-bonded supermolecules of form [pyridinium]2[M(S2C2O2)2] linked by B(OH)2⋯carboxylate synthons to form a stepped chain. These chains pack in layers superimposed so as to afford short metal⋯metal contacts of length 3.6–4 A between layers. The structure of 5 is isomorphous with that of salts 6–8 and 10 but with a different pattern of NH hydrogen bonding as a result of the different isomer of pyridinium boronic acid present.

The crystal structures of both a symmetric and an unsymmetric platinum--alkynyl compound with terminal iodophenyl functionalities have been determined, and found to exhibit an attractive interaction between the iodine atom and the carbon-carbon triple bond of the alkynyl ligand.

Addition of C2(SiMe3)2 to [Ru5(µ5-C2)(µ-PPh2)2(µ-SMe)2(CO)11]1 affords an isomeric mixture of [Ru5{µ4-CCCCH(SiMe3)}(µ-PPh2)2(µ-SMe)(µ3-SMe)(CO)10]2, alkaline hydrolysis of which gives the first stable butatrienylidene complex [Ru5(µ4-CCCCH2)(µ-PPh2)2(µ-SMe)(µ3-SMe)(CO)10]3; carbonylation of 3 affords produces the spiked-rhomboidal pentanuclear complex [Ru5(µ5-CCCCH2)(µ-PPh2)2(µ-SMe)2(CO)11]4; the X-ray structures of 3 and 4 are reported.

Addition of ButNC to [Ru5(µ5-C2)(µ-SMe)2(µ-PPh2)2(CO)10] 1 results in expansion of the Ru5 polygon and flattening of the C2Ru5 cluster so that in the product 2 one carbon atom acquires a planar tetracoordinate configuration; reversible loss of CO from 2 affords a CNBut derivative of 1.

Addition of PhCCR (R = H, Ph)to [Ru5(µ5-C2)(µ-SMe)2(µ-PPh2)2-(CO)10] 1 results in the formation of [Ru5(µ5-CCCPhCR)(µ-SMe)2(µ-PPh2)2-(CO)10](R = H 2, Ph 3), the µ5-CCCPhCR ligand being formed by coupling of the alkyne with the C2 ligand of 1; in 2 the pentagonal Ru5 cluster of 1 is retained while 3 an extra Ru–Ru bond is formed, yielding an envelope-type structure; corresponding differences in the attachment of the organic ligand to the Ru5 cluster are found.

The reaction between [Ru5(µ3-CCH2)(µ3-SMe)2(µ-PPh2)2(CO)10] and [Fe2(CO)9] afforded the electron-rich mixed-metal cluster [FeRu5(µ4-CCH2)(µ3-SMe)(µ-SMe)(µ-PPh2)2(CO)13], with a symmetrical µ4-vinylidene ligand; the metal core consists of an Ru5 bow-tie, the central and two wing-tip atoms of which are attached to the Fe atom.

Reactions of [Mn(CO)11(NCMe)][Mn= Ru3, Os3, Re3(µ-H)3, or Ru4(µ-H4)4] with the linear bis(phosphine) PPh2C2C2PPh2(bdpp) afford the ‘barbell’ complexes [{Mn(CO)11}2(µ-bdpp)][Mn= Ru31(38), Os32(68), Re3(µ-H)34(44), or Ru46(39%)]. The monosubstituted complexes [Mn(CO)11(bdpp)][Mn= Os33 or Re3(µ-H)35] were isolated when an excess of bdpp was used. Reactions of 3 with [M3(CO)11(NCMe)][M3= Ru3 or Re3(µ-H)3] afforded the mixed-metal complexes [{Os3(CO)11}(µ-bdpp){M3(CO)11}][M3= Ru 7(40) or Re3(µ-H)38(63%)]. In a similar fashion [{Re3(µ-H)3(CO)11}(µ-bdpp){Ru3(CO)11}]9 was prepared (38%) from 5 and [Ru3(CO)11(NCMe)]. When a solution of 1 in CH2Cl2 was gently heated under a nitrogen purge the C4 complex [{Ru3(µ-PPh2)(CO)9}2(µ3:µ3-C4)]10 was produced in 73% yield. Without purging, the yield is much reduced; a minor product from the reaction is [{Ru4(µ-H)(CO)12}{µ4-PPh(C6 H4)C2C2PPh2}{Ru3(CO)11}]. 11. Complex 11 contains an Ru3(CO)11 moiety linked via a PPh2C2C2PPh(C6H4) ligand to an Ru-spiked Ru3 cluster. One of the C2 units is attached in a µ-σ,σ,η2-vinylic mode to the spike Ru and to two of the three Ru atoms in the closed triangular core. When 11 was recrystallised from CH2Cl2–MeOH the complex [{Ru4(µ3-OMe)(µ-PPh2)(CO)10}(µ4-CCH-µ-η2-C 2){Ru2(µ-PPh2)(CO)6}]12 was formed. This complex contains an Ru4 rhombus, opposite faces of which carry µ3-OMe and a µ4-vinylidene ligand; the latter is attached via a C–C single bond to the binuclear fragment. The complex [{Os3(µ-PPh2)(CO)9}2(µ3:µ3-C4)]13 was obtained (78%) by pyrolysis of 2 in refluxing toluene. The structures of complexes 6 and 10–13 were determined by single-crystal X-ray studies.

The pentanuclear C2 complex [Ru5(µ5-C2)(µ-SMe)2(µ-PPh2)2(CO)11]1 is a source of novel cluster frameworks which incorporate the C2 ligand as a collar; this is exemplified by the structures of [FeRu5(µ6-C2)(µ-SMe)2(µ-PPh2)2(CO)14]2 and [Co4Ru5(µ10-C2)(µ3-SMe)2(µ-PPh2)2(µ-CO)7(CO)11]4, obtained from reactions between 1 and [Fe2(CO)9] or [Co2(CO)8], respectively.

Several complexes of the acetylenic ditertiary phosphine, Ph2PC2C2PPh2, containing Mo, W, Fe, Ru or Au have been prepared; one CC triple bond in the Mo, W or Fe derivatives has been co-ordinated to Co2(CO)6 or Pt(PPh3)2 groups. Crystal structure determinations of [{Fe(CO)4}2(µ-PPh2C2C2PPh2)]3 and [Co2{µ-η2-[(OC)5W(PPh2)]CC [C2(PPh2)W(CO)5]}(CO)6]7 show that the P-bonded M(CO)n groups take up transoid positions; in 3, the PCCCCP chain, which is situated about a centre of inversion, is nearly linear [P–C–C, 173.2(5); C–C–C 179.7(6) for molecule a and 174.7(5) and 177.6(6)°, respectively, for molecule b] with CC distances of 1.192(7)A[1.201(6)A, molecule b]. In 7, co-ordination of the Co2(CO)6 group to one CC bond lengthens that bond by 0.13 A, compared with the unco-ordinated CC bond, and induces bend-back of the substituents of 141–143(1)°(PPh2) and 145–146(1)°(C2PPh2). Crystals of 3 are triclinic, space group P, a= 11.261(1), b= 12.456(2), c= 13.061(2)A, α= 79.23(2), β= 75.73(1), γ= 78.75(2)°, Z= 2; 2870 data were refined to R= 0.042, R′= 0.046. Crystals of 7 are triclinic, space group P, a= 17.940(4), b= 19.695(4), c= 16.449(2)A, α= 111.92(1), β= 108.83(1), γ= 100.29(2)°, Z= 4; 5942 data were refined to R= 0.055, R′= 0.056.

Addition of Me2S2 to Ru5(µ5-C2PPh2)(µ-PPh2)(CO)131 resulted in a sequence of Ru–Ru bond cleavage and formation reactions; the structures of two of the products, Ru5(µ-C2)(µ-SMe)2(µ-PPh2)2(CO)123 and Ru5(µ5-C2)(µ-SMe)2(µ-PPh2)2(CO)114, which contain dicarbon (C2) attached to open and closed Ru5 pentagons, respectively, are described.

The kinetics of the decomposition of a series of alkali-metal oxalate perhydrates and their related hydrates have been studied by a combination of thermogravimetric analysis, differential scanning calorimetry, and optical microscopy. The behaviour of the perhydrates is strikingly similar to that of the related hydrate (where this exists). The kinetic formulations which best fit the decompositions have been ascribed and activation energies obtained for experiments carried out in a static atmosphere (Ea= 64–208 kJ mol–1 for perhydrates, 98–250 kJ mol–1 for hydrates).