Antony J. Deeming

Addition reactions of a polynuclear osmium hydrido compound leading to associative carbonyl substitution and catalytic alkene isomerisation

Abstract The ability of H2Os3(CO)10 to undergo addition reactions under mild conditions allows associative CO substitution via isolable intermediates of the type H2Os3(CO)10 (L = CO, PMe2Ph, PPh3 or PhCN) whose spectra and structures are discussed. It is probable that simple addition of alkenes to H2Os3(CO)10 is in part responsible for its facile catalysis of alkene isomerisation. The kinetics of catalytic conversion of terminal to internal alkenes and of allylic alcohols to aldehydes or ketones are reported and discussed. The reactions of H2Os3(CO)10 with allylic halides to give the complexes HOs3X(CO)10 and Os3X2(CO)10 where X = Cl, Br or I are described. Compound H2Os3(CO)10 complies with the 18ρ-rule but nevertheless has a chemistry much like that of coordinatively unsaturated molecules.

Palladation behaviour of 8-methyl-, 8-ethyl-, and 8-isopropyl-quinolines and some of their 2-substituted derivatives

Abstract 8-Methyl- and 8-ethyl-quinolines give cyclopalladation products with palladium acetate by CH bond cleavage at the 8-substituent, but 8-isopropylquinoline does not. The influence on cyclometallation of introducing 2-substituents (Me, Br, CHO, CHNMe, CH2OH, CO2H) in these quinolines is described. The first three substituents totally prevent cyclopalladation whereas metallation at the 8-substituent proceeds smoothly when the 2-substituent is CHNMe, CH2OH or CO2H. The products are characterised spectroscopically and there is a discussion of the dynamic 1H NMR behaviour of the cis and trans isomers of [Pd(OAc)(CH2C9H6N]2 formed from 8-methylquinoline. Evidence is presented that the cyclopalladation reaction takes place for a three-coordinate palladium(II) intermediate with the reacting hydrocarbon group entering the vacated fourth coordination site.

A new type of pyridine-2-thionato bridge: X-ray crystal structure of the complex [Re2(MepyS)2(CO)6] where MepyS is the 6-methylpyridine-2-thionato ligand

Abstract [Re2(CO)10] reacts with pyridine-2-thione (pySH) in refluxing xylene to give the dinuclear cluster [Re2(pyS)2(CO)6] which contains three fused four-membered rings. The novel five-electron donating pyS bridges are easily cleaved by ligand addition and in redistribution reactions with [Re2(MepyS)2(CO)6], the 6-methyl-substituted derivative for which the X-ray structure is reported.

Unsaturated nitrogen-containing ligands in triosmium clusters derived from trimethylamine and N,N-dimethylbenzylamine☆

Abstract Trimethylamine and N,N-dimethylbenzylamine react with Os 3 (CO) 12 by elimination of alkane or H 2 to give the compounds HOs 3 (μ 2 -RCNMe)(CO) (R = H or Ph), Hos 3 (μ 2 -CNMeR)(CO) 10 (R = Me or PhCH 2 ) and HOs 3 (μ 3 -HCNMe)(CO) 9 . An ortho-metallated product from PhCH 2 NMe 2 , cis-Os(o-C 6 H 4 CHNMe) 2 (CO) 2 , also contains an unsaturated ligand and is formed in very low yield, and indeed no products not containing CN double bonds were observed. Metallation at atoms ??? to the heteroatom and the formation of unsaturated ligands are almost completely dominant features of the chemistry, the latter being a characteristic of triosmium systems not shared by many others. Some of these products are also formed from benzylidenemethylamine with a mononuclear product, cis-Os(o-C 6 ???I ??? CHNMe) 2 (CO) 2 in very low yield.

Oxidative addition of 2-formyl-furan and related pyrrole and thiophene compounds at triosmium clusters

Abstract The bridging acyl complexes [Os 3 H(μ-COC 4 H 3 X)(CO) 10 ] (X = NH, O, or S) have been prepared by oxidative addition of the 2-formyl derivatives of pyrrole, furan, or thiophene (C 4 H 3 XCHO) at [Os 3 (CO) 10 (MeCN) 2 ] with cleavage of the aldehydic CH bonds. On heating double decarbonylation of the acyl complexes occurs, to afford high yields of the compounds [Os 3 H 2 (CO) 9 (μ 3 -C 4 H 2 X)], reported previously for X = NH or O. For X = NH, two isomers with this formulation were characterised by 1 H NMR and IR data; the one containing the μ 3 -2,3-C 4 H 3 N ligand isomerises to one containing μ 3 -1,2-C 4 H 3 N. The direct reaction of pyrrole with [Os 3 (CO) 12 ] has been re-examined at lower temperatures than before, and observed to give new products, including [Os 3 H(CO) 10 (C 4 H 4 N)], which contains a bridging non-aromatic tautomeric form of pyrrole. The ability of Os 3 clusters to stabilize non-aromatic tautomers of aromatic ligands is discussed.

para-Ethynyl aniline as a building block for fully π-conjugated ligands and acetylide complexes: crystal structures of trans-[Pt(PPh3)2(CCC6H4NH2)2] and [(μ-H)Ru3(CO)9(μ3-CCC6H4NH2)]

para-Ethynyl aniline has been prepared, structurally characterised and investigated as a building block towards fully pi -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, Bu-n), cis-[Pt(eta (2)-dppe)(C=CC6H4NH2)(2)], all trans-[Ru(CO)(2)(PEt3)(2)(C=CC6H4NH2)(2)] and [(muH)Ru-3(CO)(9)(mu C-3=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

Extrusion of selenium and tellurium atoms from selenophene and tellurophene by reaction with trinuclear iron, ruthenium, and osmium clusters: crystal structures of [Os6(μ-H)(μ3-Se)(μ4-C4H3)(CO)20] and of [Ru4(μ3-Se)μ-C4H4)(CO)11]

Abstract The trinuclear carbobyl clusters [Fe 3 (CO) 12 ], [Ru 3 (CO) 12 ], [Os 3 (CO) 11 (MeCN)], and [Os 3 (CO) 10 (MeCN) 2 ] react with selenophene and tellurophene ( cyclo -C 4 H 4 X, X = Se or Te) under mild conditions to give compounds containing the open-chain ligands CHCHCHCHX or the fragments X, C 4 H 4 , C 4 H 3 , or H as bridging ligands. The following compounds were isolated and characterised: [Os 3 (CO) 10 (C 4 H 4 X)], 1 where X = Se (X-ray structure reported previously) and 8 where X = Te, [Os 6 H(Se)(C 4 H 3 )(CO) 20 ], 2 , [Os 2 (CO) 6 (C 4 H 4 Se)], 3 , [Ru 2 (CO) 6 (C 4 H 4 )], 4 , [Ru 4 (CO) 6 (C 4 H 4 )], 4 , [Ru 4 (Se)(CO) 11 (C 4 H 4 )], 5 , [Fe 2 (CO) 6 (C 4 H 4 )], 6 , and [Fe 2 (CO) 6 (C 4 H 4 Se)], 7 . The clusters 2 and 5 were shown by single-crystal X-ray diffraction methods to have had both SeC bonds broken to give μ 3 -Se ligands in each case. Compound 2 contains an interesting μ 4 -C 4 H 3 ligand linking two Os 3 units through a μ-alkylidyne bridge, a σ-OsC bond, and an η 3 -allyl component. Compound 5 has a μ-C 4 H 4 ligand of a type previously found to be formed by alkyne coupling. The other compounds were characterised spectroscopically.

Conversion of the clusters [Os3(1,3-diyne)(CO)10] into bis(alkynyl) clusters by carboncarbon bond cleavage

Abstract The symmetrical 1,3-diynes, RC2C2R (RMe, Et, Ph, But, SiMe3), react with [Os3(CO)10(MeCN)2] to give the clusters [Os3(μ3,η2-RC2C2R)(μ-CO)(CO)9]. The μ3,η2-coordinated alkyne group does not exchange with the non- coordinated one. As a consequence the unsymmetrical diyne, PhC2C2SiMe3, gives non-interconverting and separable isomers of [Os3(μ3η2-PhC2C2SiMe3)(μ-CO)(CO)9] which differ only in which of the two alkyne groups is coordinated. Thermal decarbonylations of the compounds containing RC2C2R (RPh, But or SiMe3) and the isomers containing the unsymmetrical diyne, PhC2C2SiMe3, lead by carboncarbon bond cleavage to bis(alkynyl) clusters of the type [Os3(μ,η1-C2R1)(μ3,η2-C2R2)(CO)9] where R1R2Ph, But SiMe3 and only one isomer from the mixed diyne with R1Ph and R2SiMe3. XRD studies on this isomer established that C2SiMe3 is in the triply-bridging position and C2Ph in the doubly-bridging position. Although the C2Ph ligand is only bonded through the α- carbon atom, we consider it to be σ, π-bonded and a three-electron donor. It spans two osmium atoms that are not bonded (Os…OS=3.297(2) A). Thermolysis of the EtC2C2Et complex leads to carbon-hydrogen rather than carboncarbon cleavage to give the allenyl cluster [Os3H(μ3,η2,η2-MeCHCCC2Et)(CO)9], while the MeC2C2Me cluster decarbonylates to [Os3(C4Me2)(CO)9] of unknown structure but which may be [Os3(CMe)(CC2Me)(CO)9].

Triosmium clusters containing diphosphine and triphosphine ligands

Abstract The isomeric butadiene compounds 1,1- and 1,2-[Os 3 (C 4 H 6 )(CO) 10 ] and the acetonitrile compound 1,2-[Os 3 (CO) 10 (MeCN) 2 ] react with the diphosphines Ph 2 P(CH 2 ) n PPh 2 ( n = 2, 3 or 4) to give separable isomers of [Os 3 (CO) 10 (diphosphine)] in which the diphosphine is either bridging or chelating, whereas dppm ( n = 1) gives only the 1,2-isomer. The mono-acetonitrile compound [Os 3 -(CO) 11 (MeCN)] reacts to give two series of compounds: [Os 3 (CO) 11 (diphosphine)], containing one coordinated and one free phosphorus atom, and [Os 6 (CO) 22 (diphosphine)] with two Os 3 (CO) 11 groups bridged by the diphosphine. The triphosphine, Ph 2 PCH 2 CH 2 PPhCH 2 CH 2 PPh 2 (triphos), reacts similarly to give two separable isomers of [Os 3 (CO) 11 (triphos)] and two inseparable isomers of [Os 6 (CO) 22 (triphos)]. Whereas [Os 3 (CO) 11 (dppm)] readily undergoes decarbonylation to give 1,2-[Os 3 (CO) 10 (dppm)], other compounds of the type [Os 3 (CO) 11 (diphosphine)] are not decarbonylated under the same conditions, but react with Me 3 NO to give the 1,2-but not the 1,1-isomers of [Os 3 (CO) 10 (diphosphine)].

Ortho-metallation reactions of 2-substituted pyridines, 1,2-, 1,3-, and 1,4-diazines, and 2,2′-bipyridyl with triosmium clusters. Crystal and molecular structure of nonacarbonyl-µ-(2,2′-bipyridyl-6-yl)-µ-hydrido-triangulo-triosmium(3Os–Os)

2-Methyl- or 2-benzyl-pyridine, and 1,2-, 1,3-, and 1,4-diazines all react like pyridine itself with [Os3(CO)10-(C8H14)2](C8H14= cycle-octene) to give complexes of the type [Os3H(CO)10(µ-L)] where Lisa 2-metallated heterocycle. The 1H n.m.r.spectrum of the 2-benzylpyridine complex shows that µ-L is in a locked configuration on the n.m.r. time-scale and does not alternate its bonding between the two Os atoms it bridges. 2,2′-Bipyridyl reacts with [Os3(CO)12] to give the related red complex [Os3H(CO)9(C10H7N2)] which contains the chelating bridging 6-metallated bipy ligand as established by a single-crystal X-ray structure determination. The crystals are monoclinic, space group P21/c, with a= 9.113(2), b= 13.157(2), c= 18.209(2)A, β= 91.59(2)°, and Z= 4. The structure was refined to R= 0.0427 for 3 550 observed reflections. The structure of [Os3H(CO)9-(C10H7N2)] is rather like those of compounds [Os3H(CO)10,X] and in particular where X = 2-pyridyl except that in the nonacarbonyl complex described here the ortho-metallated pyridine ring is part of a 2,2′-bipyridyl chelating ligand.