The complex [(triphos)Fe(CO)H-2] 1 has been prepared and characterised by H-1 and P-31 NMR and IR spectroscopies, and by single-crystal X-ray diffraction. Complex 1 is fluxional at ambient temperatures in solution; NMR spectral simulation shows that both a Bailar twist of the triphos ligand and pairwise hydride exchange contribute to this fluxionality, with the latter process apparently more facile. DFT-calculated vibrational frequencies for I indicate that both these processes are thermally accessible at ambient temperatures. The X-ray crystal structure of complex 1 shows that the triphos ligand adopts a fac arrangement in a distorted octahedral structure, with the two hydride ligands mutually cis, and a non-linear Fe-C-O moiety. Protonation of complex 1 with hexafluoroisopropanol (HFIP) initially produces a hydrogen-bonded intermediate; reaction proceeds further to give the cationic complex [(triphos)Fe(CO)H(eta(2)-H-2)](+) 2. Complex 2 decomposes above 250 K in solution, but has been characterised by NMR spectroscopy. T-1 (min) and J(HD) measurements indicate that 2 contains a stretched dihydrogen ligand, with r(HH) = 1.03 angstrom, in apparent disagreement with DFT calculations that suggest that the equilibrium H-H distance is 0.85 angstrom, indicative of a conventional dihydrogen moiety. However, the very shallow nature of the potential energy surface for the RU(eta(2)-H-2) moiety can account for this difference between experimental and calculated values. The experimental and computed structural and spectroscopic features deduced for 1 and 2 are compared with those of their known ruthenium analogues, and are discussed in the context of other hydride and dihydrogen complexes of the Group 8 metals.

Two routes to 1,1-dithiolate complexes cis-[Ru(CO)(2)(S(2)X)(2)] [X = NMe(2), OEt, PPh(2), P(OEt)(2)] are presented. From the reaction of NH(4)S(2)P(OEt)(2) with the ruthenium(II) complex generated upon reduction of RuCl(3).3H(2)O by CO in 2-methoxyethanol, along with the expected mononuclear product, cis-[ Ru(CO)(2){eta(2)- S(2)P(OEt)(2)}(2)], binuclear [Ru(CO){eta(2)-S(2)P(OEt)(2)}{mu, eta(1), eta(2)-S(2)P(OEt)(2)}](2) was also produced. The latter has been crystallographically characterized and shows a trans-arrangement of carbonyls and cis- arrangement of terminal and bridging dithiolate ligands.

The coordination chemistry of bis(di-ortho-tolylphosphino)methane (dotpm) has been studied. It is an excellent chelating ligand and a range of low-valent mononuclear complexes have been prepared; cis-[M(CO)4(η2-dotpm)] (M = Cr, Mo, W; 1–3), [CpRuCl(η2-dotpm)] (4), and cis-[MX2(η2-dotpm)] (M = Pt, X = Cl, Br, I; 5a–5c, M = Pd, X = Cl; 6). The backbone protons are relatively acidic and can be deprotonated using n-BuLi or LiN(SiMe3)2. Subsequent alkylation by RX (X = halogen; R = Me, Et, CH2Ph) affords cis-[M(CO)4(η2-Rdotpm)] (M = Cr, Mo, W, R = Me; 7–9, M = Mo, W, R = Et, CH2Ph; 12–15), [CpRuCl(η2-Medotpm)] (10), and cis-[PtI2(η2-Medotpm)] (11). Thermolysis of cis-[Mo(CO)4(η2-Medotpm)] (8) yields what is believed to be the coordinately and electronically unsaturated complex [Mo(CO)3(η2-Medotpm)] (16), suggesting that derivatives of dotpm (cone angle 194°) are bulky enough to stabilize a 16-electron complex. Crystal structures of 2, 3, 7–9, 13, and 14 have been determined (diphosphine bite angles ranging from 66.58(3)° to 70.96(5)°.Key words: diphosphine, transition metal, bulky, carbonyl, ortho-tolyl.

Cleavage of P=Se bonds occurs readily in the room-temperature treatment of [Os-3(CO) (10)(MeCN)(2)] with Ph3P=Se to give three new compounds, [Os-3(mu(3)-Se)(2)(CO)(8)(PPh3)] (2), [Os-3(mu(3)-Se)( mu(3)-CO)(CO)(7)(PPh3)(2)] (5) and [Os3(mu-OH)(2)(CO)(8)(PPh3)(2)] (6), respectively, and three known compounds, [Os-3(mu(3)-Se)(2)(CO)(9)] (1), [Os-3(mu(3)-Se)(mu-CO)(2)(CO)(7)(PPh3)] (3), and 1,2-[Os-3(CO)(10)(PPh3)(2)] (4). No evidence for any product containing a co-ordinated Ph3P--Se ligand was obtained. The analogous reaction between [OS3(CO)10(MeCN)2] and Ph3P=S produces five new compounds [Os-3(mu(3)-S)(2)(CO)(8)(PPh3)] (7), [Os-3(mu(3)-S)(mu-CO)(2)(CO)(7)(PPh3)] (8), [Os-3(mu(3)-S) (mu(3)- CO)(CO)(7)(PPh3)(2)] (9), [Os-3(mu(3)-)(2)(CO)(7)(PPh3)(2)] (11) and compound 6 in addition to the known compound 4. Treatment of with Me3NO at 50 degrees C gives the trinuclear cluster [Os-3(mu(3)-Se)(2)(CO)(7)(PPh3)(NMe3)] (13) and the hexanuclear cluster [Os-6(mu(3)-Se)(4)(CO)(14) (PPh3)(2)] (12). Treatment of compound 1 with PPh3 and Me3NO at room temperature gives [Os-3(mu(3)-Se)(2)(CO)(7)(PPh3)(2)] (10). Compound 2 reacts with PPh3 similarly to give 10. Compound 3 reacts with elemental selenium at 110 degrees C to give 2. The new compounds 2, 5, 6 and 8 were characterized by single-crystal X-ray diffraction. The compounds 3, 5, 8 and 9 contain Os-3(mu(3)-S) or Os-3(mu(3)-Se)cluster cores with three metal-metal bonds while 2, 7, 10, 11 and 12 contain Os-3(mu(3)-S)(2) or Os(mu(3)-Se)(2) cores two metal-metal bonds. The two hydroxy ligands in the triosmium cluster 6 bridging the open osmium-osmium edge and are probably derived from water. A study of the dynamic exchange of PPh3 ligands in 5 is also reported. (c) 2005 Elsevier B.V. All rights reserved.

Treatment of trans-1,2-bis(2-pyridyl)ethene (C12H10N2) with the labile cluster [Os-3(CO)(10)(CH3CN)(2)] in refluxing THF generated the products: [Os-2(mu:eta(4)-C12H10N2)(CO)(6)] (1) and [Os-3(mu:eta(4)-C12H10N2)(CO)(10)] (2). When the reaction is carried out in refluxing acetonitrile the products [Os-3(mu-H)(2)(mu(3):eta(3)-C12H10N2)(CO)(8)] (3), [Os-3(mu-H)(mu(3):eta(4)-C12H9N2)(CO)(8)] (4) and {Os-3(mu-CO)(mu(3):eta(3)-C12H10N2)(CO)(8)} (5) are obtained in addition to compounds 1 and 2. The X-ray structures for 1, 3 and 4 are reported. We have established that both pyridine nitrogen atoms are co-ordinated in all five complexes. I and 2 contain the ligand incorporated in a doubly-bridging manner, and for clusters 3, 4 and 5 hydrogen atom transfer at the central ethene group has lead to bridging alkylidene and vinyl systems within triply-bridging ligands. (C) 2004 Elsevier B.V. All rights reserved.

Traps-[RuCl2(CO)(2)(PEt3)(2)] reacts with two equivalents of a series of 1,1-dithiolate ligands to form the bis(dithiolate) complexes, cis-[Ru(CO)(PEt3)(S2X)(2)] (X = CNMe2, CNEt2, COEt, P(OEt)(2), PPh2). Two intermediates have been isolated; trans-[Ru(PEt3)(2)Cl-(CO){S2P(OEt)(2)}] and trans-[Ru(PEt3)(2)(CO)(eta(1)-S2COEt)(eta(2)-S2COEt)], allowing a simple reaction scheme to be postulated involving three steps; (i) initial replacement of cis carbonyl and chloride ligands, (ii) substitution of the second chloride, (iii) loss of a phosphine. Thermolysis of cis-[Ru(CO)(PEt3)(S2CNMe2)(2)] with Ru-3(CO)(12) in xylene affords trinuclear [Ru-3(mu(3)-S)(2)(PEt3)(CO)(8)] as a result of dithiocarbamate degradation. Crystal structures of cis-[Ru(CO)(PEt3)(S2X)(2)] (X = NMe2, COEt), trans-[Ru(PEt3)(2)Cl(CO){S2P(OEt)(2)}], trans[Ru(PEt3)(2)(CO)(eta(1)-S2COEt)(eta(2)-S2COEt)] and [Ru-3(mu(3)-S)(2)(PEt3)(CO)(8)] are reported. (c) 2005 Elsevier B.V. All rights reserved.

Two methods were used to synthesise [Ru-3(mu-H)(2)(mu(3)-PPh)-(CO)(7) (mu-dppm)] (3) (dppm = Ph2PCH2PPh2), the subject of this paper. Treatment of [Ru-3(CO)(10)(mu-dppm)] (1) with phenylphosphane in refluxing THF gave both [Ru-3(mu-H)(2)(mu-PHPh)-(CO)(8)(mu-dppm)] (2) and [Ru-3(mu-H)(2)(mu(3)-PPh)(CO)(7)(mu-dppm)] (3). Cluster 2 converts to 3 in refluxing THF. Alternatively the phenylphosphinidene cluster [Ru-3(mu-H)(2)(mu(3)-PPh)(CO)(9)] (4), prepared by the reported method of treating [Ru-3(CO)(12)] with phenylphosphane, reacts with dppm to produce cluster 3. The single-crystal X-ray structures of 2 and 3 are reported. Hydride mobility in [Ru-3(mu-H)(2)(mu(3)-PPh)(CO)(7)(mu-dppm)] (3) was analysed by variable-temperature H-1 and P-31(H-1) NMR methods. The variations in the spectra with temperature could not be interpreted by a single process, several of which were explored and which gave inadequately matching computed and experimental spectra. However, the spectra were successfully analysed by two concurrent processes, both involving the migration of hydride ligands between Ru-Ru edges. The faster process leads to the exchange of the nonequivalent phosphorus nuclei but not hydride exchange, whereas the hydrides are also exchanged in the slower process. Both processes require hydride ligand migration from one Ru-Ru edge to a vacant one. The hydride ligand bridging the same pair of ruthenium atoms as the dppm ligand is the slower to migrate. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).

Treatment of the labile compound [Os-3(CO)(10)(CH3CN)(2)] with 2,3-bis(2-pyridyl)pyrazine (C14H10N4) in dichloromethane at room temperature gave the cluster [Os-3(C14H10N4)(CO)(10)] (1), which contains the chelating ligand co-ordinated axially through one of the pyridine rings and equatorially through a pyrazine nitrogen atom while one of the pyridine rings remains unco-ordinated. Thermolysis of 1 leads to loss of CO and yields two structural isomers of [Os-3(mu-H)(mu,eta(3)-C14H9N4)(CO)(9)] (2) and (3). Isomer 2 contains an orthometallated 2-pyridyl group and a co-ordinated 2-pyridyl which is not orthometallated. A seven-membered chelate ring is formed and the pyrazine ring is uncoordinated. On the other hand, isomer 3 contains a 2-pyridyl-1,4-pyrazine fragment metallated in the pyrazine ring to form a five-membered chelate ring with the one pyridine ring remaining unco-ordinated. The molecular structures of 1-3 were confirmed by X-ray crystallographic studies. (C) 2004 Elsevier B.V. All rights reserved.

The cluster [Os(3)(CO)(10)(MeCN)(2)] reacts readily with azulene in refluxing cyclohexane to give the oxidative addition product [Os(3)(mu-H)(mu(2)-eta'-C(10)H(7))(CO)(10)] 1 which was shown by its X-ray crystal structure to contain the C(5) ring of the azulenyl ligand bonded through a single carbon atom at the 1-position. We propose that the Compound is zwitterionic, with the 7-membered ring a tropylium cation and the 5-membered ring coordinated as a mu-alkylidene to the metal cluster, which carries a formal negative charge. Thermal loss of one CO ligand leads by further oxidative addition to the known cluster [Os(3)(mu-H)(2)mu(3)-eta(1):eta(1):eta(1)-C(10)H(6))(CO)(9)] 2. (C) 2004 Elsevier B.V. All rights reserved.

The valence saturated benzothiazolide triosmium cluster [Os-3(CO)(10)(mu-eta(2)-C7H4NS)(mu-H)] (1) reacts with tetramethylthiourea in refluxing toluene to give [Os-3(CO)(8)(mu-eta(2)-C7H4NS)(eta(2)-SCNMe2NMeCH2)(mu-H)(2)] (5), which exists as a mixture of two isomers in solution, whereas the electron-deficient cluster [Os-3(CO)(9)(mu(3)-eta(2)-C7H4NS)(mu-H)(2)] (2) reacts with tetramethylthiourea in refluxing cyclohexane to give two new compounds [Os-3(CO)(8)(mu-eta(2)-C7H4NS)(eta(2)-SCNMe2NMeCH2)(mu-H)(2)] (6) and [Os-3(CO)(9)(mu-eta(2)- C7H4NS)(eta(1)-SC(NMe2)(2))(mu-H)] (7). In contrast, the reaction of [Os-3(CO)(9)(mu(3)-eta(2)-C7H3(2-CH3)NS)(mu-H)](3) with tetramethylthiourea in refluxing cyclohexane at 81 degreesC, gives only [Os-3(CO)(9)(mu-eta(2)-C7H3(2-CH3)NS)(eta(1)-SC(NMe2)(2))(mu-H)] (8) in 15% yield. Compound 7 converts into 6 in refluxing toluene whereas a similar thermolysis of 8 results non-specific decomposition. All the compounds have been characterized by elemental analysis, IR, H-1 NMR and mass spectroscopic data together with single crystal X-ray diffraction analysis for 5 and 7. Both compounds 5 and 6 contain a cyclometallated tetramethylthiourea ligand which is chelating at the rear osmium atom and are structurally very similar. In 5, the benzothiazolide ligand is coordinated to Os-3 triangle via the nitrogen lone pair and C(2) carbon atom of the heterocyclic ring whereas in 6 the ligand is coordinated to the Os-3 triangle via the nitrogen lone pair and the C(7) carbon atom of carbocyclic ring. In 7 and 8, the tetramethylthiourea ligand is coordinated at an equatorial site of the osmium atom which is also bound to the nitrogen atom of the benzothiazolide ligand. (C) 2004 Elsevier B.V. All rights reserved.

The reaction of (2-aminophenyl)phosphine P(2-NH2C6H4)H2 with [Os3(CO)10(MeCN)2] gives the compounds [Os3(CO)11{P(2-NH2C6H4)H2}] (1), [1,2-Os3(CO)10{P(2-NH2C6H4)H2}2] (2) and [Os3(μ-H)(CO)10{μ-P(2-NH2C6H4)H}] (3). Thermolysis of compounds 1 and 3 in cyclohexane affords in quantitative yields [Os3(μ-H)2(CO)9{μ3-P(2-NH2C6H4)}] (4). However, the direct reaction of P(2-NH2C6H4)H2 with [Ru3(CO)12] yields only the nonacarbonyl species [Ru3(μ-H)2(CO)9{μ3-P(2-NH2C6H4)}] (5). The phosphino group coordinates more favorably than the amino group and PH bond activation is favored over amino coordination.

Turnstile rotation is suppressed in the equatorially substituted cluster [Os(3)(mu-H)(2)(mu(3)-S)(CO)(8){(S)-PhCHMeNH(2)}] which was separated by HPLC into two diastereomers which do not interconvert at room temperature and epimerize only slowly at 90 degreesC.

para-Ethynyl aniline has been prepared, structurally characterised and investigated as a building block towards fully π-conjugated multifunctional ligands and complexes. Palladium–copper catalysed coupling with aryl halides affords a number of new amino-substituted aryl acetylenes, while using [Ni(CO)2(PPh3)2] as a catalyst, cyclotrimerisation and dimerisation to give an ene-yne were competitive. Reaction of para-ethynyl aniline with low-valent metal centres affords acetylide complexes trans-[Pt(PR3)2(CCC6H4NH2)2] (R=Ph, Bun), cis-[Pt(η2-dppe)(CCC6H4NH2)2], all trans-[Ru(CO)2(PEt3)2(CCC6H4NH2)2] and [(μ-H)Ru3(CO)9(μ3-CCC6H4NH2)]. The bis(acetylide) trans-[Pt(PPh3)2(CCC6H4NH2)2] has been used to prepare extended chain complexes with amide, imine, imino-phosphorane and ferrocenyl imine units being generated. Attempts to prepare polymers via reaction with terephthaloyl chloride lead only to the formation of oligomers with an average of four monomer units.

Room temperature reaction of K(2)[Ru(3)(CO)(11)] with the molybdenum(VI) bis(imido) complexes Mo(NAr)(2)Cl(2)(dme) (Ar = C(6)H(3)X(2)-2,6; X = Me, Pr(i), Cl; dme = 1,2-dimethoxyethane) affords new high-low valent clusters Ru(3)(CO)(12){Mo(NAr)(2)} which adopt a butterfly arrangement of metal centres with [Ru(3)(CO)(12)](2-) acting as a ligand at a molybdenum(VI) centre.

Reaction of the cluster [Os3(CO)10(MeCN)2] with benzo[b]thiophene (C8H6S) leads to the hydridic decacarbonyl and nonacarbonyl species [Os3(μ-H)(CO)10(μ-C8H5S)] (1) and [Os3(μ-H)2(CO)9(μ3-C8H4S)] (2), formed by cleavage of one and two C–H bonds respectively. In addition, the decacarbonyl complex [Os3(CO)10(μ-C8H6S)] (3) is formed by C–S bond cleavage. Thermal treatment of compound 1 affords clusters 2 and 3 in good yields, and at room temperature the slow, clean and complete conversion of 1 into 3 is observed. From dibenzothiophene (C12H8S), [Os3(μ-H)2(CO)9(μ3-C12H6S)] (4) is obtained by C–H bond cleavage at one benzo group and its structure has been established by X-ray crystallography. The organic ligand is bonded through σ-Os–C bonds to two Os atoms and an η2-contact with the third, and the C–C bond between the two metal-bonded carbon atoms lies essentially parallel to one Os–Os bond.

Diastereomeric orthometallated products, formed by treating [Os3(CO)10(MeCN)2] with (S)-nicotine or (R)-1-(4-pyridyl)ethanol, have been partially separated by TLC but completely so by HPLC. The two diastereomers of [Os3(µ-H){µ-(R)-NC5H3CH(OH)Me-4}(CO)10] 1 and 2 and four isomers of [Os3(µ-H){µ-(S)-NC5H3C4H7NMe}(CO)10], 3 to 6, two diastereomers each for the products of metallation at the 2 and 6 positions respectively, have been separated and characterized by circular dichroism (CD) spectra to obtain their relative configurations. The CD spectra in the 230–500 nm wavelength range are totally characteristic of the configuration of the Os3CN group at atoms. A crystal structure determination for isomer 2 has allowed absolute configurations of all isomers to be established. There is little enantioselection in the orthometallation process and no detectable interconversion of isomers. The compound [Os3(µ-H)2{µ-(S)-NC5H3C4H7NMe}2(CO)8] was also obtained as a complex isomeric mixture which was not separated.

Treatment of [Mn2(CO)10] with diphenyl(2-pyrrolyl)phosphine (Ph2P-2-C4H3NH) leads to simple substitution products, the product of PC bond cleavage [Mn2(μ-H)(μ-PPh2)(CO)8], but the most interesting product (21%) is the trinuclear compound [Mn3(μ3-P,N,η5-Ph2PC4H3N)(CO)11], the X-ray structure of which shows it to contain the bidentate ligand, 2-diphenylphosphinoazacyclopentadienylmanganese tricarbonyl, Mn(η5-Ph2PC4H3N)(CO)3, which bridges across a Mn2(CO)8 unit as a novel four-electron donating chiral N,P-ligand.

Replacement of a CO ligand by MeCN in the capped clusters [M(3)(mu-H)(2)(mu(3)-X)(CO)(9)] (M = Ru, X = NSO(2)C(6)H(4)Me-4 or M = Os, X = S) allows reductive coupling of alkynes (RC=CH, R = H or Ph) to give regioselectively the 1,3-diene clusters [M(3)(C(4)H(4)R(2))(mu(3)-X)(CO)(8)], with the diene mu-eta(2),eta(2)-coordinated for ruthenium and eta(4) for osmium.

Thermal and photochemical reactions of diphenyl-2-thienylphosphine (L) with [Mn(2)(CO)(10)] gave simple substitution products [Mn(2)(CO)(10-n)L(n)] 1 (n = 1) and 2 (n = 2) with ligand L co-ordinated through the phosphorus atom. Under forcing conditions (refluxing xylene) oxidative addition with P-C cleavage occurred to give the mu-2-thienyl complex [Mn(2)(CO)(6)(mu-PPh(2))(mu-eta(1):eta(5)-C(4)H(3)S)] 3. Loss of CO and P-C bond cleavage do not occur so easily in the case of [Re(2)(CO)(10)]. UV Treatment of the rhenium carbonyl with L gave [Re(2)(CO)(8)(mu-P,S-Ph(2)PC(4)H(3)S)] 4, in which the ligand L is bridging through the two heteroatoms. Oxidative addition occurs internally at about 180 degrees in decane with rupture of a P-C bond to produce an isomer of 4, [Re(2)(CO)(8)(mu-PPh(2))(mu-eta(1):eta(1)-C,S-C(4)H(3)S)] 5. Crystal structures revealed a novel form of bridging of L co-ordinated through P and S in 4 and two different modes of 2-thienyl bridge (mu-eta(2):eta(5) and mu-eta(1):eta(1)-C,S) in 3 and 5 respectively. With the previously known mu-eta(1):eta(2)-bridging form of thienyl, these new compounds 3 and 5 provide three distinct type of thienyl bridge. The type of bridge which is formed depends upon the electronic requirements of the metal atoms and the span between them.