Owen Johnson

Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 52. Synthesis and reactions of the compounds [RuW(µ-CR)(CO)3(η-C5H5)(η5-C2B9H9Me2)](R = C6H4Me-4 or Me); crystal structures of [RuW(µ-CC6H4Me-4)(CO)3(η-C5H5)(η5-C2B9H9Me2)] and [N(PPh3)2][RuW(µ-CC6H4Me-4)(µ-σ,η5-C2B9H8Me2)(CO)3(η-C5H5)]

Treatment of the compounds [N( PPh3)2[W(CR)(CO)2(η5-C2B9H9Me2)](R = C6H4Me-4 or Me) with [Ru(CO)(NCMe)2(η-C5H5)][BF4] in CH2Cl2 affords the dimetal complexes [RuW(µ-CR)-(CO)3(η-C5H5)(η5-C2B9H9Me2)]. The structure of the product with R = C6H4Me-4 has been established by a single-crystal X-ray diffraction study. The Ru–W bond [2.803(2)A] is spanned by the p-tolymethylidyne group [Ru–µ-C 2.20(7); W–µ-C, 1.890(6)A]. The tungsten atom carries two CO ligands and the η5-C2B9H9Me2 cage. The ruthenium atom is ligated by a CO group and the cyclopentadienyl anion, and also by the unique B–H bond of the open pentagonal face of the icosahedral η5C2B9H9Me2 fragment [B–Ru, 2.400(7); B–H, 1.33; Ru–H, 1.67 A]. Deprotonation of [RuW(µ-CC6H4Me-4)(CO)3(η-C5H5)(η5-C2B9H9Me2)], on basic alumina or by n-butyl-lithium, in the presence of [N( PPh3)2] Cl gives the salt [N( PPh3)2][RuW(µ-CC6H4Me-4)(µ-σ,η5-C2B9H8Me2)-(CO)3(η-C5H5)] which was structurally characterised by X-ray diffraction. The structure of the anion [Ru–W, 2.748(l); Ru–µ-C, 2.100(6); W–µ-C,1.941(5)A] is very similar to that of its neutral precursor, the major difference being replacement of the B–H⇀Ru three-centre two-electron bond by a direct B–Ru linkage [2.155(6)A]. The C2B9H8Me2 cage thus adopts an unusual µ-σ,η5 bonding mode at the WRu centre. Some reactions of the ruthenium–tungsten dimetal species are described, and spectroscopic data are reported and discussed.

Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 67. Reactions of the salts [X][W(CR)(CO)2(η5-C2B9H9Me2)][X = P(CH2Ph)Ph3, R = C6H4Me-4; X = NEt4, R = Ph] with bis(cyclo-octa-1,5-diene)platinum

The salts [X][W(CR)(CO)2(η5-C2B9H9Me2)][X = NEt4, R = Ph; X = P(CH2Ph)Ph3 or PPh4, R = C6H4Me-4] have been prepared, and an X-ray diffraction study has been carried out on the tetraphenylphosphonium compound. There are two very similar crystallographically independent anions, together with their associated counter ions, in the asymmetric unit of the structure. In the anion the tungsten atom carries two terminally bound carbonyl ligands (W–CO mean 2.019 A, W–C–O mean 176.9°), a p-tolylmethylidyne ligand [WCC6H4Me-4 mean 1.83(3)A], and the η5-7,8-C2B9H9Me2 cage [mean W–ligated cage atoms, 2.424 A(mean of 10)]. Treatment of the species [X][W(CR)(CO)2(η5-C2B9H9Me2)][X = P(CH2Ph)Ph3, R = C6H4Me-4; X = NEt4, R = Ph] in thf (tetrahydrofuran) with [Pt(cod)2](cod = cyclo-octa-1,5-diene) affords the complexes [P(CH2Ph)Ph3][PtW(µ-CC6H4Me-4)(CO)2(cod)(η5-C2B9H9Me2)](2a) and [NEt4][PtW(µ-CPh)(CO)2(cod)(η5-C2B9H9Me2)](2b), respectively. The cod ligand in the compounds (2) may be displaced with tertiary phosphines, but crystalline products were not obtained. Moreover, protonation of (2) led to decomposition. However, treatment of (2a) with [AuCl(PPh3)] and TIPF6, and (2b) with the gold reagent and KPF6, in thf, affords the trimetal compounds [AuPtW(µ3-CR)(CO)2(PPh3)(cod)(η5-C2B9H9Me2)](R = C6H4Me-4 or Ph), which were fully characterised. The n.m.r. data (1H, 13C-{1H}, 195Pt-{1H}, and 31P-{1H}) for the complexes are reported.

Reconsideration of the crystal structure refinement of the complex [PPh4][W(CC6H4Me-4)(CO)2(η5-C2B9H9Me2)]

An X-ray crystal structure determination of [PPh4][W(CCC6H4Me-4)(CO)2(η5-C2B9H9Me2)] has been reported recently in this journal. The data have now been re-evaluated and the amended structure is described.

The crystal structure of [Rh3(μ3-CO)2(η-C5Me5)3] and reactions of the unsaturated metal clusters [MM′2(μ3-CO)2(η-C5Me5)3] (M = M′ = Rh; M = Co or Ir, M′ = Rh) with hydrogen☆

Abstract An X-ray crystallographic study of the complex [Rh3(μ3-CO)2(η-C5Me5)3] has revealed that the CO ligands asymmetrically bridge the Rh3 triangle in accord with theoretical predictions. Treatment of the trirhodium compound, or the related mixed-metal complexes [MRh2-(μ3-CO)2(η-C5Me5)3] (M = Co or Ir), with hydrogen gas gives the species [MRh2(μ-H)2(μ-CO)(μ3-CO)(η-C5Me5)3]; the molecular structure of the dihydridotrirhodium cluster has been established by X-ray diffraction.

Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 68. Reactions between nonacarbonyldi-iron and the salts [NEt4][W(CR)(CO)2(η5-C2B9H9Me2)](R = Me, Ph, or C6H4Me-4); crystal structures of [NEt4][FeW{µ-CH(C6H4Me-4)}(µ-σ:η5-C2B9H8Me2)(µ-CO)(CO)5] and [NEt4][Fe2W(µ3-CPh)(µ-σ:σ′,η5-C2B9H7Me2)(CO)8]

Treatment of the compound [NEt4][W(CMe)(CO)2(η5-C2B9H9Me2)] with [Fe2(CO)9] in tetrahydrofuran at room temperature affords the trimetal compound [NEt4][Fe2W(µ3-CMe)(µ-σ:σ′,η5-C2B9H7Me2)(CO)8]. Similar reactions between [Fe2(CO)9] and the salts [NEt4][W(CR)(CO)2(η5-C2B9H9Me2)](R = Ph or C6H4Me-4) afford mixtures of the di- and tri-metal compounds [NEt4][FeW{µ-CH(R)}(µ-σ:η5-C2B9H8Me2)(µ-CO)(CO)5] and [NEt4][Fe2W(µ3-CR)(µ-σ:σ′,η5-C2B9H7Me2)(CO)8]. The structures of the two species [NEt4][FeW{µ-CH(C6H4Me-4)}(µ-σ:η5-C2B9H8Me2)(µ-CO)(CO)5] and [NEt4][Fe2W(µ3-CPh)(µ-σ:σ′,η5-C2B9H7M2)(CO)8] have been established by X-ray diffraction. In the anion of the former, the Fe–W bond [2.625(1)A] is spanned by an alkylidene group C(H)C6H4Me-4 [µ-C–Fe 2.153(5), µ–C–W 2.172(5)A], and a carbonyl ligand [µ-C(O)–Fe 2.021(4), µC(O)–W 2.172(5)A; W–C–O 149.3(3), Fe–C–O 133.2(3)°]. The tungsten atom carries two terminally bound CO groups, and is η5-co-ordinated by the nido face of the carbaborane cage. The latter is linked to the iron via a σ bond involving a boron atom adjacent to a carbon atom in the face of the cage. The iron is ligated by three terminally bonded CO groups. In the di-irontungsten salt there is an isosceles triangle of metal atoms [Fe–W 2.645(2), Fe–Fe 2.578(2)A], capped on one side by the phenylmethylidyne group [µ3–C–Fe 2.06(1), µ3-C–W 2.029(8)A]. On the opposite side of the triangle a µ3-C2B9H7Me2 ligand is η5-co-ordinated to tungsten with two adjacent boron atoms in the nido face of the carbaborane cage forming σ bonds to the iron atoms [Fe–B 2.12(1) and 2.14(1)A]. There are eight terminally bound carbonyl groups, three attached to each iron atom, and two bonded to the tungsten atom. Treatment of [NEt4][Fe2W(µ3-CMe)(µ-σ:σ′,η5-C2B9H7Me2)(CO)8] in tetrahydrofuran with [AuCl(PPh3)], in the presence of TIPF6, affords a tetranuclear metal cluster complex [AuFe2W(µ3-CMe)(µ-σ:σ′,η5-C2B9H7Me2)(CO)8(PPh3)]. The n.m.r. data (1H, 13C-{1H}, and 11B-{1H}) for the new compounds are reported and discussed.

The structure and reactivity of dipyrido[1,2-a : 1′,2′-d]pyrazinium cations

The crystal structure of 6,12-dihydrodipyrido[1,2-a : 1′,2′-d]pyrazinium dibromide (1) has been determined by X-ray crystallography. In aqueous or methanolic solution (1) behaves as a strong acid and is in equilibrium with the monocation (2); the proton-transfer kinetics have been studied using stopped-flow methods and the N-protonated form of (2) has been isolated as the di-iodide. Reduction of (1) with borohydride yields a mixture of isomeric octahydro derivatives which do not appear to re-aromatise to compound (3). The relative enthalpies of formation of (1) and (3) have been calculated using MNDO and are compared to related heteroaromatic compounds.

Reactions of amine hydrochlorides with phosphorus trichloride oxide; preparation and X-ray crystal structure of 2,4,6-trichloro-1,3,5-triphenyl-1,3,5,2λ5,4λ5,6λ5-triazatriphosphorinane 2,4,6-trioxide (PhNPOCl)3

The reaction of aniline hydrochloride with POCl3has been shown to yield the trimeric cyclophosphazane (PhNPOCl)3in good yield and purity, in opposition to the earlier results of Michaelis which assigned a dimeric structure to the product. The trimeric nature has been confirmed by 31P n.m.r. spectroscopy, mass spectroscopy, and an X-ray crystallographic structure determination. The analogous 4-methylphenyl and 4-methoxyphenyl compounds have been similarly prepared. The products are relatively inert to nucleophiles but reactions with ethoxide and hydroxide ions yield products which give evidence for a mechanism involving ring contraction by transannular attack of nitrogen on phosphorus.

Chemistry of di-and tri-metal complexes with bridging carbene or carbyne ligands. Part 38. Ruthenium–tungsten compounds: crystal structures of [RuW-(µ-Cl)(µ-CMe)(Cl)(CO)2(PPh3)2(η-C5H5)] and [RuW2(µ3-C2Me2)(CO)7(η-C5H5)2]

Purple crystals of the compound [RuW(µ-Cl)(µ-CMe)(Cl)(CO)2(PPh3)2(η-C5H5)] are obtained by placing a diethyl ether solution of [W(CMe)(CO)2(η-C5H5)] above a tetrahydrofuran (thf) solution of [RuCl2(PPh3)3]. The ruthenium–tungsten complex has been characterised by an X-ray diffraction study. The Ru–W bond [2.769(1)A] is spanned by the Cl and CMe ligands [C–W 1.942(11), C–Ru 2.021(9), Ru–Cl 2.447(3), W–Cl 2.497(3)A]. In addition to the cyclopentadienyl ligand the W atom carries terminal Cl and CO ligands which exhibit a positional disorder between two effectively interchangeable sites in the complementary ratios 3: 1. The ruthenium atom is ligated by two PPh3 groups and a CO group. Treatment of the ruthenium–tungsten complex with MeCCMe affords [RuW(µ-Cl)(µ-CMe)(Cl)(CO)2(PPh3)(η-C2Me2)(η-C5H5)], possible structures for which are discussed on the basis of n.m.r. data. The compound [W(CMe)(CO)2(η-C5H5)] reacts with the species [Ru(CO)n(PPh3)5–n](n= 2 or 3) to afford an insoluble trimetal complex [RuW2(µ3-C2 Me2)(CO)6(PPh3)(η-C5H5)2]. The PPh3 group in the latter may be displaced with CO or PEt3 to give the species [RuW2(µ3-C2Me2)(CO)6(L)(η-C5H5)2](L = CO or PEt3), but the reaction with CO is reversed unless the PPh3 is removed by complexation. The structure of the heptacarbonyl complex has been established by X-ray diffraction. The molecule has a triangular metal core [Ru–W 3.026(1) and 2.835(1), W–W 2.944(1)A] bridged by the MeCCMe ligand in such a manner that the alkyne lies essentially parallel to one of the Ru–W vectors. Hence this ligand is σ bonded to the ruthenium atom and to one tungsten centre [C–RU 2.068(9), C–W 2.169(9)A] while being η2 co-cordinated to the other tungsten atom [C–W mean 2.281 (9)A]. The ruthenium atom carries three terminally bound CO ligands, while the tungsten atoms are each ligated by a C5H5 and two CO groups. Three of the four CO ligands bound to tungsten semi-bridge the edges of the metal–atom triangle. The complexes [RuW2(µ3-C2Me2)(CO)6(L)(η-C5H5)2] undergo dynamic behaviour in solution, as revealed by n.m.r. studies.

Perfluoroalkyl-1,2,3-triazines: novel nucleophilic attack on ring nitrogen

Syntheses of trifluoro- and perfluoroisopropyl-1,2,3-triazine derivatives and the unusual nucleophilic attack by a perfluoroalkyl anion and phenylmagnesium bromide on ring nitrogen are described; cheletropic addition of 2,3-dimethylbutadiene to ring nitrogen and an analogous addition of 2,3-dimethylbut-2-ene occur.