W. Edward Lindsell

Synthesis of 1,3-Diynes in the Purine, Pyrimidine, 1,3,5-Triazine and Acridine Series

Abstract A range of conjugated 1,3-diynes, R1CCCCR2, has been prepared that incorporate the following heteroaromatic units as head groups of the substituents R1 and/or R2: pyrimidinyl, purinyl, 2,4-diamino-1,3,5-triazinyl and acridinyl. Compounds containing the first three groups as terminal heterocyclic substituents in both R1 and R2 are bonded through methylene linkers {(CH2)n, n=1, 4 or 9} to the 1,3-diyne; also reported are amphiphilic species with R2=n-C10H21 and a single heteroaromatic head group in chain R1. Compounds in the acridine series are also amphiphiles and contain quaternised 1′-(9-acridinylamino)- and 1′-(6-chloro-2-methoxyacridinylamino)- terminal substituents linked by PEG and methylene units to the diyne function. The new diynes have been synthesised by oxidative coupling of the corresponding ω-heteroaromatic functionalised 1-alkyne or by transformation of terminal groups on preformed diynes.

Reversible syntheses of mono-(cyclopentadienyl)rhodium-tri-ruthenium cluster complexes and (η-C5Me5)2Rh2Ru2(CO)7; crystal and molecular structures of CpRhRu3{μ-H}2{μ-CO}(CO)9, Cp = η-C5H5 or η-C5Me5 and (η-C5Me5)Rh{μ-H}2Ru3{μ-H}2(CO)9

Abstract The mixed metal complexes CpRhRu 3 {μ-H} 2 {μ-CO}(CO) 9 , ( 3a : Cp = η-C 5 H 5 ; 3b : Cp = η-C 5 Me 5 ) 4b : (η-C 5 Me 5 )RhRu 3 {μ-H} 4 (CO) 9 , 5 : (η-C 5 Me 5 ) 2 Rh 2 Ru 2 (CO) 7 ) are formed when H 2 is bubbled through solutions of Ru 3 (CO) 12 and the respective CpRh(CO) 2 at 70–90°C. These are easily disrupted at 25°C back into the starting materials under an atmosphere of CO. Using 13 CO, the starting materials are obtained with complete 13 CO exchange. While CpRh(CO) 2 undergoes exchange at 25°C with 13 CO at atmospheric pressure, Ru 3 (CO) 12 does not, nor does it exchange in the presence of simply an added amount of CpRh(CO) 2 . Attachment of the CpRh moiety to the Ru 3 skeleton as in the products obtained in this work thus leads, under 13 CO, to the completely enriched starting materials Ru 3 ( 13 CO) 12 and CpRh( 13 CO) 2 . Structures of three new products have been determined using a Picker (FACS-1) four circle automated diffractometer and graphite-monochromatized Mo- K α radiation. For 3a , 3831 unique reflections with I > 3σ( I ) were used in the refinement; final discrepancy indices, R = 0.030 and R w = 0.050. Complex 3a crystallizes in the monoclinic space group P 2 1 / n ; cell dimensions a 8.1856(5), b 15.0706(10), c 16.3013(12) A, and β 91.033(1)°; calculated density 2.49 g cm −3 . For 3b , 4801 unique reflections with I > 3σ( I ) were used in the refinement; final discrepancy indices, R = 0.026 and R w = 0.042. Complex 3b crystallizes in the monoclinic space group P 2 1 / n in a cell having the dimensions of a 8.7580(5), b 14.5578(8), c 19.829(1) A, and β 97.591(2)°; calculated density 2.18 g cm −3 . For 4b , 6756 unique reflections with I > 3σ( I ) were used in the refinement; final discrepancy indices, R = 0.030 and R w = 0.040. Complex 4b crystallizes in the monoclinic space group P 2 1 / a ; cell dimensions a 17.470(1), b 18.451(1), c 17.200(1) A, and β 114.684(1)°; calculated density 2.10 g cm −3 . Metal atoms in all three structures were located by direct methods (MULTAN80). All other nonhydrogen atoms were then located by difference maps. Hydrogen atoms bridging various edges of the clusters were located after all hydrogen atoms in the η-C 5 H 5 (= Cp) or η-C 5 (CH 3 ) 5 (= Cp★) groups were refined isotropically in calculated positions. Each of the crystals studied consists of discrete molecules of the complexes, each with a triangle of ruthenium atoms capped by a CpRh or Cp★Rh group. Isomeric structures are observed for 3a and 3b . In the former, a CO group is found bridging between one Ru atom and the Rh atom while one each of two cluster-bound hydrogen atoms bridge two separate edges of the Ru 3 triangle. In 3b , both a CO group and one of the cluster-bound hydrogen atoms are found bridging between Rh and two separate Ru atoms of the Ru 3 triangle. The remaining cluster-bonded hydrogen atom is found bridging one edge of the Ru 3 triangle. In 4b , two of the cluster-bound hydrogen atoms are found (one each) on two edges of the Ru 3 triangle. The other two are found bridging each of two of the RuRh bonds. The metal—metal separations in the three structures are summarized as follows. Unbridged RuRu and RhRu fall in the ranges 2.765(1) to 2.813(1) A and 2.707(1) to 2.752(1) A, respectively; the Rh-μ-(CO)-Ru separations are 2.727(1) (in 3a ) and 2.7515(1) (in 3b ). Ru-μ-(H)-Ru separations fall in the range 2.870(1) to 2.938(1) A while Rh-μ-(H)-Ru fall in the range 2.871(1) to 2.9169(1) A.

Synthesis and characterization of cobalt and molybdenum complexes derived from linear conjugated diynenes, triynedienes and tetraynetrienes

Abstract Z -1,6-Bis(trimethylsilyl)hexa-1,5-diyn-3-ene ( 2a ), E -hexa-1,5-diyn-3-ene ( 3b ) and related compounds ( 3a , c and d ) were synthesized by standard methods. The Grignard reagent ( 3e ) derived from 1-phenylhexa-1,5-diyn-3-ene ( 3d ) was coupled with E -1-chloro-4-phenyl-1-buten-3-yne to give E , E -1,10-diphenyldeca-1,5,9-triync-3,7-diene ( 4 ) and with E -1,2-dichloroethene to give E , E , E -1,14-diphen-yltetradeca-1,5,9,13-tetrayne-3,7,11-triene ( 5 ). Hexa-1,5-diyn-3-ene complexes coordinated to one ( 7a , 8 ) and two ( 6a-d ) hexacarbonyldicobalt units were prepared from the appropriate ligands and octacarbonyldicobalt. Tris- ( 9 ) and tetrakis- ( 10 ) hexacarbonyldicobalt complexes of the triynediene ( 4 ) and tetraynetriene ( 5 ) ligands were prepared similarly. Mono ( 7b ) and bis ( 6e ) di-η 5 -cyclopentadienyltetra-carbonyldimolybdenum complexes of E -1,6-bis(trimethylsilyl)hexa-1,5-diyn-3-ene were prepared by treating free diynene ( 3a ) with the appropriate amount of [(η 5 -C 5 H 5 )Mo(CO) 2 ] 2 . Spectroscopic characteristics (NMR, IR, UV) of the complexes are presented and discussed.

Synthesis and dynamic nuclear magnetic resonance studies of pentafluorobenzenethiolate complexes of molybdenum and tungsten. The crystal and molecular structures of [W(SC6F5)3(CO)(η5-C5H5)]·0.5CH2Cl2and [N(PPh3)2][Mo(SC6F5)4(η5-C5H5)]

The reaction between [WBr3(CO)2(η5-C5H5)] and excess of Tl(SC6F5)(CH2Cl2, 20 °C) affords Tl[W(SC6F5)4(η5-C5H5)](2b) as the major product and [W(SC6F5)3(CO)(η5-C5H5)](3) as the minor product. Complex (3) has been structurally characterised as its 0.5 CH2Cl2 solvate by X-ray diffraction. Chiral molecules of [W(SC6F5)3(CO)(η5-C5H5)] adopt a distorted square-based ‘piano-stool’ geometry with the trans W–S bond [2.443 6(15)A] longer than the cis W–S bonds (mean 2.358 A). The SC6F5 ligands lie with S–C bonds approximately in the plane of the square base and, all C6F5 groups have the same rotational orientation about the central W atom. However, dynamic 19F n.m.r. studies of (3) reveal that two isomeric forms exist at low temperature due to different orientations of the SC6F5 ligands but these undergo exchange at ambient temperature as a result of rotation about the W–SC6F5 bonds or inversion at sulphur. Similar studies of complex (2b) established that apparent rotation of the SC6F5 groups is solvent dependent and occurs in conjunction with ionic dissociation into Tl+ and [W(SC6F5)4(η5-C5H5)]–. The TlI in (2b) and related complexes Tl[Mo(SC6F5)4(η5-C5H5)] and Tl[Mo(SC6F5)2(CO)2(η5-C5H5)] can be replaced by non-co-ordinating cations to give X+[M(SC6F5)4(η5-C5H5)]–[M = Mo, X = NBun4(4a) or N(PPh3)2(4b); M = W, X = NMe4] and N(PPh3)2+[Mo(SC6F5)2(CO)2(η5-C5H5)]– which also exhibit fluxional behaviour according to 19F n.m.r. studies. The structure of complex (4b), determined in the solid state by X-ray diffraction, comprises discrete ions [(Ph3P)N(PPh3)]+ and [Mo(SC6F5)]4[(η5-C5H5)]–. The complex anion has a ‘piano-stool’ geometry with a square base defined by four SC6F5 ligands (mean Mo–S 2.420 A) and the C6F5 groups form a ‘swastika-like’ arrangement about the square plane. Reactions of (2b) with tertiary phosphines (L) in CH2Cl2 at 20 °C afford 1:2 adducts Tl[W(SC6F5)4L2(η5-C5H5)][L = PPh3(6b), PMe2Ph (6c), or PEt3(6d)]. Dynamic 19F n.m.r. studies established a different structure for (6b) in solution compared to (6c) and (6d).

Monocyclopentadienyl pentafluorothiophenolate complexes of molybdenum and their interactions with thallium(I) ions; dynamic nuclear magnetic resonance studies and crystal and molecular structures of [TlMo(SC6F5)2L2(cp)](L = CO or SC6F5; cp =η5-C5H5)

Reactions between [MoCl(CO)3(cp)](cp =η5-C5H5) and Tl(SC6F5) afford the fully characterised complexes [TlMo(SC6F5)2L2(cp)][L = CO (1) or SC6F5(2)]. Complex (2) is formed by an oxidative substitution process and can also be obtained by reactions of Tl(SC6F5) with other molybdenum-(II), -(III), or -(IV) precursors. Molecular structures of crystalline complexes (1) and (2) have been determined by X-ray diffraction. Complex (1) contains units of [(cp)(OC)2Mo(µ-SC6F5)2Tl] in which TlI is co-ordinated by two S atoms (mean Tl–S 3.015 A) and is close to one ortho-F atom of each C6F5ring (mean Tl ⋯ F 3.095 A); intermolecular Tl ⋯ S interactions between individual units of (1) give this material an extended-chain structure in the solid state. Crystalline (2) contains discrete molecular units of [(cp) Mo(µ-SC6F5)4Tl] in which TlI is co-ordinated by four S atoms (mean Tl–S 3.272 A); these four S atoms, four closely associated o-F atoms, one from each C6F5ring (mean Tl ⋯ F 3.062 A), and the Mo atom [Mo ⋯ Tl 3.402(3)A] define a cavity in which the TlI is situated. The anion [Mo(SC6F5)4(cp)]– in (2) is acting as a polydentate ligand to Tl+. Variable-temperature 19F n.m.r. studies on complexes (1) and (2) in toluene, dichloromethane, and acetone solutions establish the occurrence both of restricted rotation of the C6F5 groups and of solvent-dependent ionic dissociation into Tl+ and [Mo(SC6F5)2L2(cp)]–. Significant ionisation occurs in the polar solvent acetone, and this is supported by conductivity measurements. Reactions of complex (1) with tertiary phosphines give products [Mo(SC6F5)(CO)2L(cp)][L = PMe2Ph (3), PMePh2(4), or PPh3(5)] with ‘four-legged piano-stool’ geometry; these complexes are principally cis isomers although minor amounts of trans isomers were detected by 1H n.m.r. spectroscopy in solutions of (3) and (5). Reaction of complex (2) with PPh3 affords a species [TlMo(SC6F5)4(PPh3)2(cp)] which variable-temperature 1H, 19F, and 31P n.m.r. studies show to exist as a mixture of two interchanging forms in solution.

Thermal and photochemical reactions of η5-cyclopentadienyl(naphthoyl)(dicarbonyl)iron complexes with alkynes: formation of benzindenones and dihydropentalenones

η5-Cyclopentadienyl(1- and 2-naphthoyl)(dicarbonyl)iron complexes (6a) and (6b) have been synthesised from the appropriate acid chlorides and sodium η5-cyclopentadienyl(dicarbonyl)iron-(1–). UV irradiation of (6a) and (6b) separately with diphenylacetylene in benzene gives 1,2-diphenyl-3H-benz[e]inden-3-one (8), and 2,3-diphenyl-1H-benz[e]inden-1-one (7) respectively, together with smaller quantities of bis(η5-cyclopentadienyl)(tetracarbonyl)di-iron. The benz[e]indenones (7) and (8) are also formed in low yield from diphenylacetylene and η5-cyclopentadienyl(1- and 2-naphthoyl)(dicarbonyl)iron complexes respectively, in hot decalin. A second product from the thermal reaction is c-4,c-6a-dihydro-4-(1- or 2-naphthyl)-2,3-diphenylpentalen-1(r-3aH)-one (9a) or (9b), respectively, incorporating a cyclopentadienyl group. A compound of the last type (9c) is also formed in a thermal reaction of η5-cyclopentadienyl(1-naphthoyl)(dicarbonyl)iron with 1-phenylpropyne. The molecular structures of (7) and (9a) were elucidated by X-ray crystallography.

Bis(η5-cyclopentadienyl) complexes of niobium(IV) and tantalum(IV); electron spin resonance and electrochemical studies and the molecular structure of [Ta(SCOPh)2(η5-C5H5)2]

Bis(η5-cyclopentadienyl) dihalides of niobium(IV) and tantalum(IV), [MX2(cp)2](M = Nb or Ta; X = Cl, Br, or I; cp =η5-C5H5) have been prepared by known methods or via metathetical displacement of chloride ligands in [MCl2(cp)2] by bromide or iodide ions. The new, characterised bis(monothiobenzoate) complexes, [M(SCOPh)2(cp)2](M = Nb or Ta), have been synthesised from [MCl2(cp)2] and TI(SCOPh) in acetone. The molecular structure of [Ta(SCOPh)2(cp)2], determined by X-ray diffraction of a single crystal [space group P21212, a= 7.8458(22), b= 19.903(4), c= 7.028(3)A, Z= 2, R= 0.031, R′= 0.037] comprises a normal, bent sandwich geometry with monodentate, S-bonded monothiobenzoate ligands. The angle S–Ta–S, 79.4(8)°, is relatively acute for a complex of type [MX2(cp)2] with a d1 electronic configuration. Comparative cyclic voltammetric studies have been performed for [MX2(cp)2](M = Nb or Ta; X = Cl, Br, I, or SCOPh) in dichloromethane solutions. Oxidation to [MX2(cp)2]+ is essentially reversible for these systems and ease of oxidation decreases with ligand X in the order SCOPh > Cl > Br > I. Reduction is irreversible in dichloromethane at room temperature for the dihalide complexes, whereas a primary, reversible reduction of [M(SCOPh)2(cp)2] may be attributed to the formation of the respective monoanions. All complexes [MX2(cp)2] have been investigated by e.s.r. spectroscopy in solutions and in frozen glasses of 2-methyltetrahydrofuran–dichloromethane. Solution spectra yield isotropic parameters gisoand Aiso(M)(M =93Nb or 181Ta) and the variation of these parameters with the nature of X in [MX2(cp)2] is discussed: values of gisoor Aiso(M) increase or decrease, respectively, with change of X in the sequence Cl, Br, I. Glass spectra of [MX2(cp)2] have been analysed in terms of the anisotropic e.s.r. parameters.

Preparation and studies of paramagnetic diene complexes of molybdenum(III); molecular and electronic structures of [MoCl2(η-C4H6)(η-C5H5)] and [Mo3(µ-Cl)(µ3-O){µ3-σ,σ:η2:η2-C4(CF3)4}(η-C5H5)3]

Reactions of complexes [MoX{η-C2(CF3)2}2(η-C5H5)] with certain dienes give the paramagnetic complexes [MoX2(η-diene)(η-C5H5)][diene = 1,3-butadiene, X = Cl (la), Br (1b), or I (1c); diene = isoprene, X = Cl (2); diene =trans-1,3-pentadiene, X = Cl (3)] characterised by elemental analysis, i.r. spectroscopy, and mass spectrometry. The structure of (1a), determined from 2 716 observed reflections measured at 185 K and refined to R= 0.0367 (R′= 0.0532), shows a molecule of near Cs symmetry. The cyclopentadienyl ligand is distorted from regular η5 bonding by slippage of the Mo atom across the ring by 0.12 A towards η3 co-ordination. The 1,3-butadiene adopts a cis-endo configuration with internal C–C bonds shorter by 0.045 A than terminal C–C bonds; the Mo–C bonds are shorter to terminal than to internal C atoms, and the butadiene is tilted away from a parallel geometry to assume a configuration with Mo which approaches a metallacyclopentene unit. Extended-Huckel molecular orbital (EHMO) calculations on complex (1a) are presented and confirm the stability of the endo conformation relative to the exo form (85 kJ mol–1). A by-product in the formation of complex (1a) is [Mo3(µ-Cl)(µ3-O){µ3-σ,σ:η2:η2-C4(CF3)4}(η-C5H5)3], (4), which has been structurally characterised as its 0.5C4H6 solvate by X-ray diffraction. The structure has been refined to R= 0.0377 (R′= 0.0488) using 4 215 data recorded at 185 K. A flattened isosceles triangle of metal atoms, base ca. 2.90 A, base–apex ca. 2.58 A, is face-capped by O and (open) edge-bridged by Cl. The C4(CF3)4 unit is symmetrically bonded to the opposite Mo3 face to the capping O atom, in a 2σ+ 4π bonding mode. EHMO calculations suggest some multiple character for the base–apex Mo–Mo bonds, but little direct bonding between the basal atoms. Complex (1a) is interconverted with Tl(SR) into [Mo(SR)2(η-C4H6)(η-C5H5)][R = C6H4Me-4 (5a)(72%) or C6F5(5b)(15%)], characterised by analysis and spectroscopy. Cyclic voltammetric studies on complexes (1a), (5a), and (5b) establish a reversible reduction process in both tetrahydrofuran and dichloromethane, and also more complex oxidations. The most easily reduced complex is (5b), whereas (5a) is most readily oxidised. Complexes (1) and (5) all show e.s.r. spectra in solution with hyperfine coupling to 95,97Mo and to ligand nuclei of 35,37Cl, 79,81Br, and diene terminal 1H atoms. E.s.r. spectra of these complexes in frozen 2-methyltetrahydrofuran are also presented. The e.s.r. results are discussed in relation to the electronic structures of the complexes, especially the nature of the singly occupied molecular orbital, as determined by EHMO calculations on complex (1a).

Reactions of tetranuclear rhodium–triruthenium clusters with di- and tri-phosphines and with alkynes

The compound [RhRu3(µ-H)2(µ-CO)(CO)9(cp)]1(cp =η5-C2H5) and an equimolar amount of diphosphine Ph2P(CH2)nPPh2[n= 1 (dppm), 2 (dppe) or 3 (dppp)] react at ambient temperature principally with cleavage of the heteronuclear cluster to form several homonuclear rhodium and ruthenium products. Isolated ruthenium clusters are simple phosphine derivatives of [Ru3(CO)12] or [Ru4(µ-H)4(CO)12], including [Ru3(µ-diphos)2(CO)8](diphos = dppm or dppe), [Ru3(µ-diphos)(CO)10] and [{Ru3(µ-diphos)(CO)9}2(µ-diphos)](diphos = dppe or dppp), and [Ru4(µ-H)4(CO)10(dppp)]. Reaction of 1 with the triphosphine MeC(CH2PPh2)3 affords hydrido-clusters [Ru3(µ-H)H(µ-triphos)(CO)8] and [Ru3(µ-H){µ-PPhCH2CMe(CH2PPh2)2(CO)8]12, the latter formed by elimination of benzene under very mild reaction conditions. The solid-state structure of cluster 12 has been determined by X-ray crystallographic analysis [monosolvate with dichloromethane, monoclinic, space group P21/n, a= 19.549(3), b= 14.2462(21), c= 16.429(4)A, β= 90.271(18)°, Z= 4, R= 0.051, R′= 0.060] and the geometrical non-rigidity of this asymmetric molecule in solution is revealed by variable-temperature 31P NMR spectroscopy. Reactions of cluster 1 with alkynes, RCCR (R = Ph or Et), give heteronuclear products, including isomers of [RhRu3(C2R2)(CO)9(cp)] and trimetallic clusters [RhRu2(C2R2)(CO)n(cp)](R = Et, n= 7; R = Ph, n= 8); from reaction of [RhRu3(µ-H)4(CO)9(η5-C5Me5)] with PhCCPh a related tetranuclear cluster [RhRu3(C2R2)(CO)9(η5-C5Me5)] is formed. A new, octahedral heteronuclear cluster [Rh2Ru4(µ-H)2(CO)12(cp)2] is also reported.

Synthesis, characterisation and optical properties of metal-containing polydiacetylenes

Soluble polydiacetylenes (CR–CC–CR′)n[R = R′=(CH2)9O2CCH2Ph (2a); R =(CH2)9CH3, R′=(CH2)8CO2CH2Ph (2b)] have been synthesized and reacted with Co2(CO)8 to introduce varying proportions of Co2(CO)6 groups, attached as Co2C2 tetrahedrane units, at the alkyne bonds of the conjugated ene–yne backbone. These metallated polymers have been characterised by analytical data and by IR, 13C[1H] NMR and UV–VIS spectroscopy. Reactions between polydiacetylenes 2a or 2b and [M2(CO)4(η5-C5H5)2](M = Mo, W) are also reported. The presence of fast optical non-linearities in these soluble polymeric materials was confirmed by fluorescence lifetime measurements and optical characterisation of the imaginary part of χ(3) These studies were conducted on a picosecond timescale to allow electronic contributions to be resolved, and the related lm χ(3) values tabulated against metal content and solution concentration.