Terminal CO Groups Research Articles

Application of the hydro(solvento)thermal technique to the synthesis of metal carbonyl chalcogenide clusters. 2. Synthesis and x-ray structures of [[Fe4Te4(CO)10]2(Te2)]2- and [[Fe2Se(CO)6]2(Se2)]2-

The hydrothermal reaction of Fe(CO)[sub 5] with Na[sub 2]Te[sub 2] in the presence of Ph[sub 4]PCl at 110[degrees]C forms (Ph[sub 4]P)[sub 2][[l brace]Fe[sub 4]Te[sub 4](CO)[sub 10][r brace][sub 2](Te[sub 2])] (I) while the reaction of Fe(CO)[sub 5] with Na[sub 2]Se[sub 2] in superheated methanol at 80[degrees]C results in (Ph[sub 4]P)[sub 2][[l brace]Fe[sub 2]Se(CO)[sub 6][r brace][sub 2](Se[sub 2])] (II). The structures of (I) and (II) were determined by X-ray single-crystal analysis. (I) crystallizes in the space group P[bar 1], and (II) in the space group P2[sub 1]/n. The [[l brace]Fe[sub 4]Te[sub 4](CO)[sub 10][r brace][sub 2](Te[sub 2])][sup 2[minus]] anion in (I) forms a ditelluride, Te[sub 2][sup 2[minus]], bridged double cubane-like structure with eight iron atoms in two Fe[sub 4]Te[sub 4] cubes being octahedrally-coordinated by briding tellurium ligands and terminal CO groups. The [[l brace]Fe[sub 2]Se(CO)[sub 6][r brace][sub 2](Se[sub 2])][sup 2[minus]] molecule in (II) adopts a double butterfly' conformation caused by an intramolecular Se-Se linkage between two Fe[sub 2]Se[sub 2](CO)[sub 6] units. All iron atoms in this structure have a distorted octahedral geometry achieved by selenium ligands, CO groups, and a Fe-Fe single bond. The average Fe-Te bond distance is 2.619(4) [Angstrom], and Fe-Se = 2.386(17) [Angstrom]. 30 refs., 4 figs., 5 tabs.

Umsetzung von alkinylphosphanen mit hauptgruppenelement-verbr:uckten eisencarbonylclustern

The tetrahedral clusters Fe 3(CO) 10(μ 3-PR) ( 1) react on thermal as well as photochemical activation with Ph 2PCCPh to give Fe 3(CO) 8(μ 3-PR)[μ 3-η 4-Ph 2PCCph(CO)] ( 3). In 3 an edge-opened iron triangle bears a μ 3-PR group on one side and the alkynylphosphane on the other side as bridging moieties. One of the terminal CO groups present in 1 in addition to being coordinated to the appropriate iron atom, is bonded to the phenylsubstituted carbon atom of the alkynylphosphane. Irradiation of the square-pyramidal cluster Fe 3(CO) 9(μ 3-P tBu)(μ 3-Se) ( 2) in the presence of Ph 2PCCPh leads to the compounds Fe 3(CO) 7(Ph 2PCCPh) 2(μ 3-P tBu)(μ 3-Se) ( 4) and Fe 3(CO) 6(Ph 2PCCPh) 3(μ 3-P tBu)(μ 3-Se) ( 5). In these clusters the square-pyramidal framework of 2 is preserved. In each case the alkynylphosphane ligands are coordinated via phosphorus only. In 4 one of these ligands is bonded to each of the two equatorial iron centres; in 5 each of the three iron atoms bears an alkynylphosphane ligand. The results are supported by conventional spectroscopic and analytical data as well as by single-crystal analyses.

Stereochemistry of the compounds [Fe 3(CO) 9XY]. Crystal and molecular structures of the mixed triiron carbonyl compounds [Fe 3(CO) 9XY] (X, Y = S, Se, or Te)

X-ray analyses of [Fe 3(CO) 9SSe], [Fe 3(CO) 9STe] and of [Fe 3(CO) 9SeTe] was performed. The three compounds are isomorphous and belong to the trielinic space group P 1 with a = 6.835(1), 6.996(1), 6.964(1) Å, b = 9.186(2), 9.367(1), 9.360(2) Å, c = 13.121(3), 13.058(2), 13.189(2) Å, α = 93.79(3), 93.23(1), 94.09(2)°, β = 94.21(3), 94.03(1), 94.54(2)° γ = 110.89(3), 111.14(1), 110.67(2)° for the SSe, STe and SeTe complexes, respectively. The structures were refined anisotropically to R = 0.026, 0.042, 0.030 for 3127 3465, 2564 observed reflections for the SSe, STe and SeTe complexes, respectively. They belong to the well known series of [Fe 3(CO) 9XY] complexes formed by an open triangle of iron atoms each linked to three terminal CO groups, with two faces capped by a chalcogen atom. The bond distances and angles of these mixed complexes are well within the ranges imposed due to the different dimensions of the chalcogen atoms. Intermolecular contacts occur when at least one chalcogen atom is tellurium. Examining some relevant geometrical features of the complexes with X,Y = S, Se, Te, NR, PR, AsR… a regular trend of the Fe-Fe distances is found, depending on the dimensions of the capping atoms; an asymmetry of the Fe-Fe distances is attributed to steric factors.

Synthesis of [Co2(µ-PPh2C3H4)(µ-PPh2)(CO)4]; its reactions with P(OMe)3and with alkynes

The bis(phosphido)-bridged complex [Co2(µ-PPh2)2(CO)6]1 undergoes an insertion reaction of allene into one of the phosphido bridges, to give the new ligand-bridged dinuclear cobalt complex [Co2(µ-PPh2C3H4)(µ-PPh2(CO)4]2 in high yield. Complex 2 reacts with P(OMe)3 to give the monosubstituted derivative [Co2(µ-PPh2C3H4)(µ-PPh2)(CO)3{P(OMe)3}]3 in which substitution has occurred at the allyl-co-ordinated cobalt atom. Complex 2 also reacts with alkynes, RCCH (RCH2OH, Me or H), which insert into the remaining phosphido bridge along with a molecule of CO to give [CO2(µ-PPh2C3H4){µ-PPh2C(O)CHCR}(CO)3](R = CH2OH 4a, Me 4b or H 4c). In the case of MeCCH which gives 4b, a second isomer, [Co2(µ-PPh2C3H4){µ-PPh2C(O)CMeCH}(CO)3]5, which differs in the mode of insertion of the alkyne, is also obtained. The isomeric complexes [Co2{µ-PPh2C(O)CHCR}(µ-PPh2)(CO)4](R = CH2OH 6a or Me 6b) and [Co2{µ-PPh2C(O)CRCH}(µ-PPh2)(CO)4](R CH2OH 7a or Me 7b), which may be regarded respectively as analogues of 4 and 5 but with a phosphido bridge and an additional terminal CO group in place of the µ-PPh2C3H4 ligand, have been prepared from [Co2(µ-RCCH)(CO)6](R CH2OH or Me) and P2Ph4. The complexes [Co2{µ-PPh2CHCRC(O)}(µ-PPh2)(CO)4](R CH2OH 8a or Me 8b), which are also isomers of complexes 6a, 7a and 6b, 7b respectively, have also been obtained in these latter reactions. The complexes 8 contain a bridging ligand which differs from that present in 6 and 7 in that the ordering of the PPh2, alkene and CO components of the bridging ligand is not the same. The crystal structures of the complexes 3 and 4c have been determined by X-ray diffraction studies.

Crystal and molecular structure of bis(μ 3-tellurido)-decacarbonyltriiron, [Fe 3(CO) 10Te 2

The tellurium complex [Fe 3(CO) 9Te 2] reacts with CO to give [Fe 3(CO) 10Te 2]. The reaction occurs via attack of CO on a peripheral iron atom of the open triangle of [Fe 3(CO) 9Te 2] with consequent rupture of an iron—iron bond. The complex lies on a crystallographic two-fold axis and contains an iron—iron bond between two Fe atoms each linked to three terminal carbonyl groups: a third Fe atom, linked to four terminal CO groups, is connected to the Fe 2 unit by two bridging Te atoms.

Thiocarbonyl complexes of iron VIII. Reaction of Fe(CO) 4CS with the halogens Cl 2, Br 2 and I 2

The halogens Br 2 and I 2 convert the thiocarbonyl complex Fe(CO) 4CS ( 1) by oxidative addition into the corresponding complexes Fe(CO) 3(CS)X 2 ( 3:XBr, I). Treatment of 3 at −80 °C with two equivalents of PPh 3 yields the thiocarbonyl complexes Fe(CO)(CS)(PPh 3) 2X 2 ( 4). The action of Cl 2 on 1 produces an unidentified black insoluble material containing terminal CO and CS groups. The compounds have been characterized by elemental analysis, IR, 31P NMR and mass spectroscopy. Based on the spectroscopic results, a cis arrangement of the halogen atoms is discussed.

Reactions of [Fe 2{μ-C(CN)SMe 2} (μ-CO)(CO) 2(Cp) 2]-SO 3CF 3 (Cp = μ-C 5H 5) with alcohols

The reactions of [Fe 2{μ-C(CN)SMe 2}(μ-CO)(CO) 2)(Cp)[in2]SO 3CF 3 (Cp = η-C 5H 5) with alcohols and alkoxides have been investigated. Nucleophilic attack of the oxygen atom on the μ-C carbon with displacement of the Me 2S molecule was observed in all cases. The resulting μ-cyanoalkoxycarbene derivatives [Fe 2{μ-C(CN)OR}(μ-CO)(CO) 2(Cp) 2] (R = Me, 2a; Et, 2b; iPr, 2c; CH 2Ph, 2d; CH 2CHCH 2, 2e; CH 2CH 2NMe 2, 2f; CH 2CH 2OH, 2g; C 6H 5, 3a; C 6H 4- o-NO 2, 3b) have been characterized spectroscopically. The complex [Fe 2{μ-C(CN)OCH 2CHCH 2}(μ-CO)(CO) 2(Cp) 2] ( 2e) undergoes a photolytically-promoted intramolecular CO substitution by the olefinic termination to give [Fe Fe{μ-C(CN)OCH 2CH CH 2}(μ-CO)(CO)(Cp) 2] ( 5), which was be subjected to an X-ray diffraction study. Some structural features were as expected, in particular the location of Cp in a cis disposition with respect to the CN group. The molecule is asymmetric as a consequence of the coordination of the allyl in the place of a terminal CO group; the configurations of the four chiral centres are discussed.

Photochemical reactions of [(η 5-C 5R 5)Mn(CO) 2(NO)] + (R 5  H 5, H 4Me, Me 5) as films and in low temperature glasses

The photolysis of [(η 5-C 5R 5)Mn(CO) 2(NO)] + (R 5  H 5, H 4Me, Me 5) was studied by Fourier transform IR spectroscopy in a low temperature 1,2-epoxyethylbenzene glass and in surface films. In each case the primary photoproduct was found to be [(η 5-C 5R 5)Mn(CO)(NO)] +. The result of subsequent photolysis was observed to be dependent on medium and temperature. In the low temperature glass, NO + was photoextruded and the resultant organometallic was {(η 5-C 5R 5)Mn(μ-CO)} 2. In the film at 77 K, two competing processes were observed: loss of NO and loss of NO +. Unlike the result in the glass, both terminal and bridging CO groups were observed following NO + loss. Exhaustive photolysis at room temperature in the film led to loss of NO + and ultimately loss of CO and the cyclopentadienyl ring.

Synthesis of phosphido-bridged multinuclear complexes via a mononuclear rhodium(I) compound: X-ray structures of Rh 3H(COD) 2(μ-CO) 2{μ-P(t-Bu) 2} 2 and [Fe(CO 3)](μ-CO){μ-P(t-Bu) 2}[Rh(CO){HP(t-Bu) 2}] (COD = 1,5-Cyclooctadiene)

The mononuclear rhodium(I) complex trans-RhCl(CO){HP(t-Bu) 2} 2 ( 1) was used to form multinuclear complexes with P(t-Bu) 2 bridges. Reaction of 1 with n-BuLi in THF yields yellow-orange crystalline [Rh(CO){HP(t-Bu) 2}] 2(μ-H){μ-P(t-Bu) 2} ( 2) (74%). Reaction of a mixture of 1 and [Rh(COD)Cl] 2 (COD = 1,5-cyclooctadiene) with n-BuLi in THF produces orange [Rh(COD)](μ-H){μ-P(t-Bu) 2}[Rh(CO){HP(t-Bu) 2}] ( 3) (46%) and dark red Rh 3H(COD) 2(μ-CO) 2{μ-P(t-Bu) 2} 2 ( 4) (25%). Reaction of 1 with Fe(CO) 5 in refluxing toluene yields orange crystalline [Fe(CO) 3](μ-CO){μ-P(t-Bu) 2}[Rh(CO){HP(t-Bu) 2}] ( 5) (85%). The structures of 4 and 5 have been determined by X-ray crystallography. Complex 2 has been described elsewhere. The proposed structure of 3 has a planar core with a P(t-Bu) 2 unit and a hydride bridging a metal-metal bond. One rhodium atom is further coordinated by a COD (1,5-cyclooctadiene) ligand, while the other rhodium atom bears a CO group and an HP(t-Bu) 2 ligand. The molecular structure of 4 consists of a linear arrangement of three rhodium atoms with single metal-metal bonds bridged by P(t-Bu) 2 and CO groups. The terminal rhodium atoms are coordinated by COD ligands. The molecular structure of 5 consists of a mixed metal dinuclear complex with a single Fe—Rh bond bridged by a P(t-Bu) 2 unit and a CO group in a butterfly configuration. The rhodium atom is further coordinated by a CO and an HP(t-Bu) 2 ligand. The iron atom bears three terminal CO groups.

A new rhenium-cobalt carbonyl cluster. X-ray crystal structure of ReCo 3(μ 3-NBu t) 2(μ-CO) 2(CO) 8

The interaction of Re(NBu t) 3Cl with dicobalt octacarbonyl in hexane gives rise to the cluster ReCO 3(NBu t) 2(CO) 10 that has the metal atoms with a “butterfly” type core together with two (μ 3-NBu t) and two (μ-CO) groups. The rhenium atom has three CO terminal groups, and the two wingtip cobalt atoms have two terminal CO groups.

Heterobinuclear IrRh, RuRh and Rulr complexes with pyrazolate bridging ligands: reactivity towards chelating diphosphines; crystal structure of [(C5Me5)Ir(µ-pz)2(µ-CO)-Ir(CO)(dppen)]BPh4·0.5MeOH [pz = pyrazolate, dppen =cis-1,2-bis(diphenylphosphino)ethylene

Complexes of general formula [LClM(µ-pz)2M′(cod)]1–5[L = C5Me5, M = Rh or Ir; L =p-cymene, Me = Ru; M′= Rh or Ir; pz = pyrazolate; cod = cycloocta-T,5-diene (not all possible combinations)] and [(MeC6H4Pri-p)Ru(µ-pz)(µ-Cl)2Rh(cod)]7 were prepared starting from mononuclear acetylacetonate and pyrazole or pyrazolate-containing moieties. Complexes 1–5 react with CO yielding derivatives [LClM(µ-pz)2M′(CO)2]8–12. Complexes [(C5Me5)ClRh(µ-pz)2Rh(CO)2]13 and [(MeC6H4Pri-p)CIRu(µ-pz)2Ir(CO)2]12 react with NaX to give [(C5Me5)XRh(µ-pz)2Rh(CO)2](X = I, 14; or N3, 15) and [(MeC6H4Pri-p)[graphic omitted]rX(CO)2](X = Br, 16; or I, 17. The dicarbonyl compound 10 and [(MeC6H4Pri-p)CIRu(µ-pz)2M′(CO)2](M′= Rh, 11; or Ir, 12) react with diphosphines (L–L) or 1,2-bis(diphenylarsino)ethane (dpae) and NaBPh4 or AgBF4 affording cationic complexes [LM(µ-pz)2(µ-CO)M′(L–L)]A 23–31[L–L = bis(diphenylphosphino)methane, 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, cis-1,2-bis-(diphenylphosphino)ethylene (dppen) or dpae; A = BPh4 or BF4(not all possible combinations)]. In this reaction intermediates [LM(µ-pz)2(µ-CO)M′(CO)(L–L)]A have been isolated in some cases. The crystal structure of one of these [(C5Me5)Ir(µ-pz)2(µ-CO)Ir(CO)(dppen)] BPh4·0.5MeOH 19 has been determined by X-ray diffraction methods. Crystals are monoclinic, space group P21/c, a= 15.996(2), b= 22.199(4), c= 18.874(3)Å, β= 115.04(1)° and Z= 4. The complex cation consists of two iridium atoms bridged by two pyrazolates and one ketonic carbonyl group. An η5-C5Me5 ligand, a chelate dppen and a terminal CO group complete the co-ordination spheres of the iridium atoms, which are separated by 3.440(5)Å.

A further study of the reaction of methylgermane with [Co2(CO)8], and some interconversions of the products. Crystal and molecular structures of [Co2{µ-Ge(Me)Co(CO)4}(CO)7] and [Co4(µ-4-GeMe)2{µ-Ge(Me)Co(CO)4}(CO)10], an edge-bridged square-bipyramidal Ge2Co4species

The compound [CoH(CO)4] has been established as a stoichiometric product in the fast reaction of GeMeH3with [Co2(CO)8] to form [Co2{µ-Ge(Me)Co(CO)4}(CO)7]1. A prolonged reaction with an excess of GeMeH3 yields [Co2{µ-Ge(Me)Co(CO)4}2(CO)6]2, accompanied by a hydride species [Co2(GeMeH)(CO)x](x= 7 or 8) when the excess is large. Heating this latter mixture yields [Co4(µ4-GeMe)2{µGe(Me)Co(CO)4}(CO)10]3, shown by X-ray crystallography to contain the Co4(µ4-GeMe)2 square-bipyramid core, edge-bridged by a µ-Ge(Me)[Co(CO)4] unit. The bridged Co atoms carry two terminal CO groups, and the non-bridged ones, three. The crystal structures of compound 1[triclinic, space group P, Z= 2, a= 8.626(6), b= 8.656(5), c= 13.381(9)A, α= 88.25(5), β= 84.72(5), γ= 66.26(4)°, R= 0.0649 for 1614 reflections with I > 3σ(I)] and 3[monoclinic, space group C2/m Z= 4, a= 12.330(6), b= 12.302(3), c= 18.815(9)A, β= 92.93(3)°, R= 0.0344 for 1136 reflections with I 3σ(I)] have been determined and are compared with that of 2, and spectroscopic properties are discussed, including heavy-atom vibrations of 1

ChemInform Abstract: Photochemistry of Dinuclear Osmium Carbonyl Complexes; Characterization of Os2(CO)8 Using Matrix Isolation.

UV photolysis of (I) and (II) isolated in argon matrices causes ejection of a CO or CH2=CH2 ligand, respectively, and formation of Os2(CO)8, which has a structure with only terminal CO groups.

Cobalt-platinum carbonyl complexes with carbido ligands. Crystal structure of the hexanuclear mixed-metal cluster [Co 3Pt 3(μ-H)(μ 6-C)(μ-CO) 4(CO) 5(PPr i3) 3

Reactions between the μ 3-methylidyne tricobalt complex [Co 3(μ 3-CH)(CO) 9] and the platinum reagents [Pt(C 2H 4) 2(PR 3)] (R = cyclo-C 6H 11 or Pr i) in light petroleum at room temperature afford the mixed-metal carbido-carbonyl clusters [Co 3Pt 2(μ-H)(μ 5-C)(μ-CO) 2(CO) 7(PR 3) 2] (R = cyclo-C 6H 11 or Pr i) and [Co 3Pt 3(μ-H)(μ 6-C)(μ-CO) 4(CO) 5(PPr i 3) 3]. The structure of the latter has been established by an X-ray diffraction study. The carbido-carbon atom is located inside the Co 3Pt 3 core, with the metal atoms occupying essentially octahedral sites and with meridional arrangements of the Co 3 and Pt 3 groups. However, the core is open, since one Pt···Pt separation (3.260(1) Å) is too long for a direct metal-metal connectivity. The other Pt-Pt distance (2.868(1) Å) is such as to suggest that this vector is bridged by the hydrido ligand; a feature confirmed by the 1H NMR data. The three platinum atoms are ligated by PPr i 3 groups. Four of the Co-Pt vectors (2.599(2)–2.661(2) Å) are bridged by CO ligands, and a fifth (2.842(2) Å) is semi-bridged. The three non-bridged Co-Pt connectivities are longer (2.937(2)–3.060(2) Å). One cobalt atom carries two terminal CO groups and the other two cobalts are each coordinated by one such group. The NMR spectra ( 1H, 13C-{ 1H}, and 31P-{ 1H}) of the new cluster compounds are reported and discussed.

The photochemistry of dinuclear osmium carbonyl complexes; characterisation of Os 2(CO) 8 using matrix isolation

UV photolysis of Os 2(CO) 9 or ((μ-C1,C2)CH 2CH 2)Os 2(CO) 8 ( 1) isolated in argon matrices causes ejection of a CO or C 2H 4 ligand respectively, and formation of Os 2(CO) 8, which has a structure with only terminal CO groups. Long wavelength irradiation of matrix isolated Os 2(CO) 8 in the presence of potential 2 electron donor ligands leads to production of Os 2(CO) 8L (L = CO, N 2 or C 2H 4), each containing a bridging CO group and a terminally bound ligand L. Photolysis using plane polarised light provides confirmation of the C 2 v structure of Os 2(CO) 9, and gives evidence favouring a D 2 h structure for Os 2(CO) 8. Prolonged UV photolysis of Os 2(CO) 9 in CO matrices leads to cleavage of the OsOs bond and production of Os(CO) 5.

Iron–iridium mixed-metal carbonyl clusters. Part 2. Synthesis and chemical behaviour of the tetranuclear complexes [FeIr3(CO)12]–, [Fe2Ir2(CO)12]2–, [Fe2Ir2H(CO)12]–, and [Fe3Ir(CO)13]–. Solid-state structures of [N(PPh3)2][FeIr3(CO)12], [NEt4]2[Fe2Ir2(CO)12], and [PPh4][Fe2Ir2(CO)12-{µ3-Au(PPh3)}

The compound [FeIr3(CO)12]– can be obtained by degradation of [FeIr4(CO)15]2– under a carbon monoxide atmosphere as well as by reduction of an equimolar mixture of [Fe(CO)5] and [Ir4(CO)12] in alcoholic NaOH under 1 atm (101 325 Pa) of carbon monoxide. The salt [N(PPh3)2][FeIr3(CO)12](1) crystallizes in the monoclinic space group P21/c with unit-cell dimensions a= 14.968(2), b= 19.892(2), c= 16.610(2)A, β= 96.10(2)°, and Z= 4. The molecular structure of the anion consists of a tetrahedron of metal atoms surrounded by twelve carbonyl groups: nine are terminally bound whereas three are bridging the edges of the FeIr2 basal face. Average bond distances are Ir–Ir 2.696, Ir–Fe 2.682, Ir–COt 1.889, Fe–COt 1.729, Ir–COb 2.154, and Fe–COb 1.887 A(b = bridging, t = terminal). The dianion [Fe2Ir2(CO)12]2–(2) was obtained by several different ways, the most selective being the condensation of [Fe2(CO)9] with [Ir(CO)4]–. The salt [NEt4]2[Fe2Ir2(CO)12](2) crystallizes in the monoclinic space group P21 with a= 9.072(5), b= 19.910(5), c= 10.094(3)A, β= 91.92(3)°, and Z= 2. The molecular structure of the dianion is based on a tetrahedral cluster of metal atoms and consists of an apical Ir(CO)3 group co-ordinated by three metal–metal bonds to a basal Fe2Ir(CO)9 fragment containing two Fe(CO)2 units and one Ir(CO)2 group linked to each other by a metal–metal bond and bridging carbonyl groups. Selected distances are: Ir–Ir 2.734(1), Fe–Fe 2.581(2), and averages Ir–Fe 2.683, Ir–COt 1.863, Fe–COt 1.722, Ir–COb 2.142, and Fe–COb 1.947 A. The salt [PPh4]2[Fe2Ir2(CO)12] reacts with [Au(PPh3)CI] to give [PPh4][Fe2Ir2(CO)12{µ3-Au(PPh3)}](3) which crystallizes in the monoclinic space group P21/c with a= 10.990(3), b= 13.693(2), c= 35.883(3)A, β= 97.39(2)°, and Z= 4. The metal framework of the anion is a trigonal bipyramid with the Au(PPh3) moiety in one of the apical positions, the other being occupied by a Fe(CO)3 group. Each edge of the equatorial triangle, formed by one iron and two iridium atoms, is spanned by a bridging carbonyl ligand, and two terminal CO groups are attached to each metal of this triangle. Selected bond distances are: Ir–Ir 2.758(1), and averages Ir–Fe 2.710, Ir–Au 2.786, Fe–Au 2.806(1), Ir–COt 1.845, Fe–COt 1.776, Ir–COb 2.113, and Fe–COb 1.996 A.

Synthesis and reactions of co-ordinatively unsaturated µ3-alkylidyne clusters; X-ray crystal structures of the phosphido bridged complexes [WFe2(µ3-CR)(µ-H)(µ-PPh2)(CO)6(η-C5H5)]and[WFe2(µ3-CR){µ-C(O)C(Me)CHMe}(µ-PEt2)(CO)5(η-C5H5)](R = C6H4Me-4)

Thermal decarbonylation (toluene, 111 °C) of the complexes [WFe2(µ3-CR)(µ-H)(µ-PR′2)(CO)7(η-C5H5)][R = C6H4Me-4,R′= Ph (2) or Et (3)] gives good yields of the co-ordinatively unsaturated, 46 cluster valence electron derivatives [WFe2(µ3-CR)(µ-H)(µ-PR2′)(CO)6(η-C5H5)][R′= Ph (4) or Et (5)]. The structure of the µ-PPh2 complex (4) was established by a single-crystal X-ray diffraction study and consists of a WFe2 triangle of metal atoms [W–Fe(1) 2.817(1), W–Fe(2) 2.523(1), and Fe(1)–Fe(2) 2.569(1)A] capped by a µ3-CC6H4Me-4 group. The W–Fe(2) bond is bridged by a µ-PPh2 ligand [W-µ–P 2.357(1), Fe(2)-µ–P 2.219(1)A] whilst a hydride ligand, which was located and refined, bridges the homonuclear Fe–Fe bond [Fe(1)–H(1) 1.73(4), Fe(2)-H(1) 1.54(6)A]. The tungsten atom carries a cyclopentadienyl ring and a terminal CO ligand. The Fe(2) centre bound to phosphorus has two terminal CO ligands, whilst the remaining Fe(1) atom has three approximately orthogonal terminal CO groups. The µ-PPh2 bridged W–Fe(2) separation of 2.523(1)A is extremely short. This suggests the presence of appreciable multiple-bond character in the W–Fe(2) bond which is consistent with the formulation of (4) as a co-ordinatively unsaturated complex. Spectroscopic data for complexes (4) and (5) reveal that in solution the hydride ligand adopts a terminal site on the Fe(1) atom. This contrasts with the bridging Fe(µ-H)Fe interaction observed in the solid state for (4). Solutions of (4) and (5) react with CO (15 min, 20 °C) to regenerate their saturated precursors (2) and (3) respectively. Dichloromethane solutions of (4) and (5) also react with alkynes (R″CCR″, R″= Me, Et, or Ph) to give the vinylacyl complexes [WFe2(µ3-CR){µ-C(O)C(R″)CHR″}(µ-PR2′)(CO)5(η-C5H5)][R′= Ph, R″= Me (6a), Et (6b), or Ph (6c); R′= Et, R″= Me (7)]. The molecular structure of the but-2-yne derivative (7) was established by a single crystal X-ray diffraction study. The structure consists of a WFe2 triangle of metal atoms [W–Fe(1) 2.808(1), W–Fe(2) 2.679(1), and Fe(1)–Fe(2) 2.673(1)A] capped by a µ3-alkylidyne ligand. One W–Fe bond is bridged by a µ-PEt2 ligand whilst the remaining W-Fe bond is bridged by a µ-C(O)C(Me)CHMe group which has been formed by coupling of hydride, but-2-yne, and CO ligands. The cis-{µ-C(O)C(Me)CHMe} ligand adopts a π-allyl η3-bonding mode to Fe(2)[Fe(2)–C(O) 2.083(5), Fe(2)–C(Me) 2.173(6), and Fe(2)–CHMe 2.186(6)A], and the C(O) end of the chain uses an orthogonal set of orbitals to η2 bond to the W atom [W–C(O) 2.011 (5), W–O 2.281 (4)A]. Protonation of the complexes (6a) and (7)(CH2Cl2, HBF4·Et2O) occurs at the oxygen atom of the cis-{µ-C(O)C(Me)CHMe} ligand affording the unsaturated µ-allylidene derivatives [WFe2(µ3-CR){µ-C(OH)C(Me)CHMe}(µ-PR′2)(CO)5(η-C5H5)][BF4][R′= Ph (8) or Et (9)]. The spectroscopic data (i.r. and 1H, 13C-{1H}, and 31P-{1H} n.m.r.) for the new WFe2 complexes are discussed and mechanisms are proposed to account for their formation.

Quantitative IR Analysis in the Picomole Range of Organometallic-Labeled Biomolecules in KBr Disks

Quantitative IR studies of materials dispersed in KBr disks are often unreliable because of variable sample homogeneity due to incomplete mechanical mixing. The inherent difficulties in this type of measurement are exacerbated when one is examining the extremely small amounts of material encountered with biological samples. We report here a simple, quantitative KBr-disk procedure for the IR detection of biologically important molecules at physiological levels (picomoles). This analytical technique is based on one's labeling the biomolecules with transition metal carbonyl fragments, such as Cr(CO)3, Mn(CO)3, and Co2(CO)6, and then taking advantage of the rapid multi-scanning capability of an FTIR spectrometer to detect the CO stretching vibrations of the organometallic labels in BKr disks of the solids from the subsequent biochemical precipitations. Metal carbonyl complexes containing terminal CO groups were selected as the IR markers because the v(CO) modes exhibit intense absorptions in the 2150-1900 cm−1 range, a region which is normally devoid of peaks associated with the vibrational modes of biomolecules, such as v(OH), v(NH), v(CH), v(C=O), v(C=C), and v(C-C). This non-radioisotopic procedure has already been successfully applied in estradiol receptor and immunoassay.

Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 95. Synthesis and crystal structures of [W2RuPt(µ-CC6H4Me-4)(µ3-CC6H4Me-4)(CO)6(PMe2Ph)(η-C5H5)2] and [W2Ru2Pt2(µ3-CC6H4Me-4)2(µ-CO)2(CO)9(η-C5H5)2

Treatment of [W2Pt(µ-CC6H4Me-4)2(CO)4(η-C5H5)2] in thf (tetrahydrofuran) with [Ru(CO)4(η-C2H4)] in light petroleum affords the tetranuclear metal cluster compound [W2RuPt(µ-CC6H4Me-4)-(µ3-CC6H4Me-4)(CO)7(η-C5H5)2]. The latter with 1 equivalent of PMe2Ph gives [W2RuPt-(µ-CC2H4Me-4)(µ3-CC2H4Me-4)(CO)6(PMe2Ph)(η-C5H5)2], the structure of which has been established by X-ray diffraction. One p-tolylmethylidyne group caps three metal atoms WRuPt [W–Ru 2.743(1), W–Pt 2.729(1), and Ru–Pt 2.875(1)A] in an essentially symmetrical manner. The ruthenium atom carries two carbonyl groups and the phosphine ligand [Ru–P 2.271(4)A]. The tungsten atom is co-ordinated by a C5H5 ring and two CO ligands, but the latter asymmetrically bridge the W–Pt and W–Ru bonds [W–C–O 160(1) and 157(1)°, respectively]. The WRuPt triangle is linked through the Pt atom to a W(CC6H4Me-4)(CO)2(η-C5H5) fragment via a W–Pt bond [2.733(1)A] and a bridging µ-CC6H4Me-4 ligand [µ-C–W 1.92(1), µ-C–Pt 2.03(1)A]. One of the CO groups attached to the W atom weakly semi-bridges the W–Pt bond [W–C–O 170(1)°]. The reaction between [Ru(CO)4(η-C2H4)] and [W2Pt2(µ-CC6H4Me-4)(µ3-CC6H4Me-4)(CO)4(cod)–(η-C5H5)2](cod = cyclo-octa-1,5-diene) gives a hexanuclear metal cluster [W2Ru2Pt2-(µ3-CC6H4Me-4)2(µ-CO)2(CO)9(η-C5H5)], the structure of which has also been determined by X-ray diffraction. For descriptive purposes, five of the metal atoms [W(2)Ru(1)Ru(2)Pt(1)Pt(2)] may be regarded as occupying vertices of a ‘trigonal bipyramid’ but one in which two of the metal–metal bonds [Pt(1)⋯ Pt(2) 3.064(4), Ru(1)⋯ Pt(2) 3.259(2)A] are absent. Allowing for this, the ruthenium atoms occupy the apical sites, and the two platinum atoms and the tungsten atom occupy equatorial sites. The Pt(1) atom, in addition to being part of the open metal framework, is attached via a WPt bond [2.663(3)A] to an external W(CO)3(η-C5H5) fragment. One of the CO ligands on this W(1) atom asymmetrically bridges the W(1)Pt(1) linkage [W(I)–C–O 156(3), Pt(1)–C–O 122(2)°]. Both ruthenium atoms carry three terminal CO groups. The Pt(2) atom, ligated only by two of the metal atoms [W(2) and Ru(2)] in the framework, carries a terminal CO group, and the Pt(2)–Ru(2) bond is bridged by a CO ligand [Ru(2)–C–O 136(3), Pt(2)–C–O 143(4)°]. The W(2) atom carries a C5H5 ring. Both p-tolylmethylidyne groups occupy triply bridging sites. These are on the same side of the Pt(1)W(2)Pt(2) plane, one ligand caps the W(2)Ru(1)Pt(1) triangle, the other spans the atoms Pt(2), W(2), Ru(1). The n.m.r. spectra of the new mixed-metal clusters are reported and discussed.

The heteronuclear cluster chemistry of the Group 1B metals. Part 11. Effect of the nature of the bidentate diphosphine ligand on the metal framework structures of the gold heteronuclear cluster compounds [Au2Ru4(µ3-H)(µ-H){µ-Ph2P(CH2)nPPh2}(CO)12](n= 1–6). X-Ray crystal structures of [Au2Ru4(µ3-H)(µ-H){µ-Ph2P(CH2)nPPh2}(CO)12](n= 1 or 2)

Treatment of acetone solutions of the salt [N(PPh3)2]2[Ru4(µ-H)2(CO)12] with a dichloromethane solution of the appropriate complex [Au2{µ-Ph2P(CH2)nPPh2}Cl2](n= 1–6), in the presence of TIPF6, affords the mixed-metal cluster compounds [Au2Ru4(µ3-H)(µ-H){µ-Ph2P(CH2)nPPh2}(CO)12][n= 1, (2); 2, (3); 3, (4); 4, (5); 5, (6); or 6, (7)] in ca. 60–70% yield. X-Ray diffraction studies on (2) and (3) reveal that the formal replacement of the two PPh3 ligands attached to the Au atoms in [Au2Ru4(µ3-H)(µ-H)(CO)12(PPh3)2](1) by Ph2P(CH2)nPPh2(n= 1 or 2) alters the capped trigonal-bipyramidal skeletal geometry adopted by (1). The cluster (2) crystallizes in two forms, monoclinic and orthorhombic, but X-ray diffraction studies on both forms show that the molecular structures adopted by (2) are closely similar in each case. The metal core of (2) consists of a square-based pyramid, defined by two Au atoms and two Ru atoms in the basal plane and a Ru atom at the apex, with the Ru3 face of this Au2Ru3 unit capped by a Ru atom [Au–Au 2.823(1), Au–Ru 2.682(1)–2.947(2), Ru–Ru 2.791(2)–3.006(2)A for the monoclinic form and Au–Au 2.833(2), Au–Ru 2.691(3)–2.862(3), Ru–Ru 2.805(4)–3.037(3)A for the orthorhombic form]. The Ph2PCH2PPh2 ligand bridges the two Au atoms, one hydrido ligand caps a Ru3 face and one bridges a Ru–Ru edge of the metal framework, and each Ru atom is ligated by three terminal CO groups. The skeletal geometry of (3) is reasonably similar to that exhibited by (1), but one of the Au–Ru distances [3.446(4)A] is too long for any significant bonding interaction between the two atoms. Thus, the metal framework of (3) is somewhat distorted towards a capped square-based pyramid [Au–Au 2.828(4), Au–Ru 2.777(4)–2.965(4), Ru–Ru 2.782(4)–3.008(4)A]. Variable-temperature 1H and 31P-{1H} n.m.r. studies show that, at ambient temperature in solution, the metal cores of (3)–(7) all undergo dynamic behaviour involving gold atom site exchange.