Lesley E. Smart

Reactions of co-ordinated ligands. Part 22. The reactivity of bis-(ethylene)(η5-indenyl)rhodium in displacement reactions with olefins, dienes, and acetylenes; crystal structure of η5-indenyl{l–2 :3–4-η4–[6-endo-propen-2-yl-1,2,3,4-tetrakis(trifluoromethyl)cyclohexa-l,3-diene]}rhodium formed in a cyclo-cotrimerisation reaction

In contrast to the η5-cyclopentadienyl analogue, both of the ethylenes in the compound bis(ethylene)(η5-indenyl)-rhodium are readily displaced by isoprene, cyclo-octatetraene, trans-penta-1,3-diene, trans,trans-hexa-2,4-diene, methylenecyclopropane, or acrylonitrile to afford respectively η5-isoprene-, l–2 : 5–6-η4cyclo-octatetraene-,η4-trans-penta-1,3-diene-, η4-trans,trans-hexa-2,4-diene-, bis(methylenecyclopropane)-, or bis(acrylonitrile)-(η5-indenyl)rhodium. Reaction (room temperature) of hexafluorobut-2-yne with η5-indenyl(η5-isoprene)-rhodium leads to a cyclo-cotrimerisation reaction and the formation of η5-indenyl{l–2: 3–4η4-[6-endo-propen- 2-yl-1,2,3,4-tetrakis(trifluoromethyl)cyclohexa-l,3-diene]}rhodium, the structure in the solid state being established by a single-crystal X-ray diffraction study. Crystals are orthorhombic, space group Pbca(no. 61), with eight molecules in a cell of dimensions a= 16.962(3), b= 29.618(5), and c= 8.596(4)A. The 1,3-diene part of the C6 ring is planar, and is η4-bonded to the rhodium atom, but the two carbon atoms originating from the isoprene bend away from the metal to produce a fold in the C6 ring at a dihedral angle of ca. 132°. The propenyl substituent lies on the same side of the C6 ring as the metal, i.e. is in an endo configuration. An 18-electron configuration for the rhodium is achieved by η5-attachment of the indenyl group, but two of these five carbon atoms are less strongly bonded than the other three. A similar reaction of hexafluorobut-2-yne with η5-indenyl(η4-trans-penta-1,3-diene)rhodium affords related isomeric complexes. A cyclo-cotrimerisation reaction has also been observed between hexafluorobut-2-yne and a co-ordinated ethylene of bis(ethylene)(η5-indenyl)rhodium. Related reactions between 3,3-dimethylbut-1-yne and bis(ethylene)(η5-indenyl)rhodium or bis(acrylonitrile)-(η5-indenyl)rhodium afford respectively [η4-1,4-bis(t-butyl)cyclohexa-1,3-diene]- and [η4-5 cyano-1,4-bis(t-butyl)cyclohexa-l,3-diene]-η5-indenylrhodium. In all of these reactions competitive cyclotrimerisation of the acetylenes occurs to give arenes. The mechanisms of these reactions are discussed.

A quantitative study of the aluminium trichloride–acetonitrile system using X-ray crystallography, electrical conductivity, aluminium-27 and chlorine-35 nuclear magnetic resonance and Raman spectroscopy. The characterization of the pentakis(acetonitrile)chloroaluminium(III) ion in the solid state and in solution

The compounds MCl3(M = Al, Ga, or In) yield electrically conducting solutions in acetonitrile. Boron trichloride gives non-conducting solutions and, contrary to previous work, this is interpreted as due to the presence of a molecular solute BCl3·MeCN. The electrical-conductivity data for AlCl3 in acetonitrile are discussed in detail and it is shown that from the results obtained it is not possible to differentiate between 1 : 1 and 1 : 2 electrolyte behaviour. Quantitative Raman and 27Al n.m.r. spectra demonstrate that ca. 70% of the aluminium in solutions of AlCl3 in acetonitrile is present in the form of [AlCl4]–. An X-ray single-crystal study of the solid adduct AlCl3·2MeCN crystallizing from such a solution shows that this adduct is correctly formulated as the auto-complex [AlCl(NCMe)5]2+2[AlCl4]–·MeCN. Further 27Al n.m.r. studies on solutions of Al[ClO4]3 in acetonitrile and of the solute AlCl[ClO4]2, in conjunction with the work on AlCl3 demonstrate that [AlCl(NCMe)5]2+ is the major cationic constituent of aluminium trichloride solutions in acetonitrile. The electrical-conductivity, Raman, and n.m.r. data on these solutions are all satisfactorily interpreted by the principal ionization scheme [AlCl(NCMe)5]2+2[AlCl4]– which is the formulation found for the crystal. The ionization of AlCl3, but the non-ionization of BCl3, in solution in acetonitrile is attributed principally to the ability of aluminium to adopt a co-ordination number of greater than four in ions such as [AlCl(NCMe)5]2+.

Evidence for the ready insertion of rhodium into a carbon–hydrogen bond of ethylene; crystal and molecular structure of µ-but-2-ene-µ-ethylene-bis-(η5-1-methylindenyl)dirhodium

But-2-yne reacts with [Rh(C2H4)2(η5-C9H7)] or [Rh(C2H4)2(η5-1-MeC9H6)] to give respectively [Rh2(CHCH2)(CMeCHMe)(η5-C9H7)2], [Rh2(C4Me4)(η5-C9H7)2], [Rh2(CHCH2)(CMeCHMe)(η5-1-MeC9H6)], and [Rh2-(C4Me4)(η5-1-MeC9H6)2] the structure of the 1-methyl analogue of the divinyl complex being established by X-ray crystallography; treatment of the dirhodium divinyl complex with carbon monoxide affords [Rh(CO)2(η5-C9H7)] and the ketone CH2CH·COC(Me)C(H)Me.

Reactions of co-ordinated ligands. Part 21. Reaction of 3,3,3-trifluoroprop-1-yne with methyl- and benzyl-dicarbonyl(η-cyclopentadienyl)iron and of hexafluorobut-2-yne with tricarbonyl(1—3-η-2-methylallyl)cobalt. Crystal and molecular structure of [1—5-η-exo-1-acetyl-2,4,6-tris(trifluoromethyl)cyclohexadienyl](η-cyclopentadienyl)iron

The u.v. irradiation of a hexane solution of 3,3,3-trifluoroprop-1-yne and [FeR(CO)2(η-C5H5)](R = Me, CH2C6H5, or C3H5) affords the vinyl complexes [Fe{C(CF3)C(H)R}(CO)2(η-C5H5)](R = Me, CH2C6H5), or C3H5) arising from cis insertion of the acetylene, and η5-pyranyl complexes [Fe{[graphic ommitted](CF3)}(–(η-C5H5)](R = Me or CH2C6H5). In the case of the methyl and benzyl system, [1–5-η-exo-1-acyl-2,4,6-tris(trifluoromethyl)cyclohexadienyl](η-cyclopentadienyl) iron complexes are also formed. An X-ray determination of the molecular structure of the acetyl compound shows that the 3,3,3-trifluoroprop-1-yne molecules have linked head to tail to form a six-membered ring of envelope conformation, with five atoms coplanar and η5-bonded to the iron atom. The cyclopentadienyl ring is likewise η5-bonded to the iron and completes a parallel-plane sandwich. The sixth carbon atom of the C6 ring bends away from the metal, and the acetyl group completes a tetrahedral arrangement around this atom, again bending away (exo configuration) in the same sense. The bond lengths in the planar portion of the C6 ring suggest extensive delocalisation. The crystals are monoclinic, space group P21/n(no. 14) with Z= 4 in a unit cell of dimensions a= 13.025(3), b= 10.432(2), c= 12.503(2)A, and β= 101.93(5)°. The structure has been solved by heavy-atom methods from 3 236 independent intensities measured on a fourcircle diffractometer and refined to R 0.056. The possible reaction paths available for the formation of these products are discussed. A reinvestigation of the reaction of hexafluorobut-2-yne with [Co(CO)3(η3-2-MeC3H4)] has afforded only the two compounds [[graphic ommitted]CH2}(CO)3] and [[graphic ommitted]CH2}(CO)3] there being no evidence for the formation of a bis-insertion product.

Reaction of low-valent metal complexes with fluorocarbons. Part 30. Bis(cyclo-octa-1,5-diene)platinum with hexafluoroacetone, 1,1 -dicyano-2,2- bis(trifluoromethyl)ethylene and N-methylhexafluoroisopropylideneamine; crystal and molecular structures of [Pt2{(CF3)2CO}(1,5-C8H12)2] and [Pt·C(CF3)2·O·C(CF3)2O·(1,5-C8H12)]

Reaction of [Pt(1,5-C8H12)2] with hexafluoroacetone affords, depending on reaction conditions, the complexes [Pt2{(CF3)2CO}(1,5-C8H12)2], [P[graphic omitted](1,5-C8H12)], and [P[graphic omitted]H- 1,5-C8H12)] and [P[graphic omitted](1.5-C8H12)]. The structural identities of the first two complexes have been established by the analysis of single-crystal X-ray data. The dinuclear complex is monoclinic, space group P21/c with four molecules in a unit cell of dimensions a= 9.917(3), b= 14.957(6). c= 13.358(3)A; β= 102.18(2)°. The structure has been solved by conventional heavy-atom methods from 2 083 diffracted intensities and refined to R 0.038 (R′ 0.044). The molecule contains an approximate mirror plane formed by the two platinum atoms [Pt–Pt 2.585(1)A] and the carbon and oxygen atoms of the hexafluoroacetone molecule, with the cyclo-octa-1,5- diene molecules symmetrically bonded to each platinum atom in the tub configuration.Crystals of the second complex are triclinic, space group P with two molecules in a unit cell of dimensions a= 8.212(3), b= 9.329(2), c= 12.610(3)A: α= 91.87(2). β= 102.10(2). γ= 111.25(3)°. The structure has been solved from 2 659 diffracted intensities to R 0.029 (R′ 0.035) by conventional methods. The platinum atom forms part of a five-membered condensed (head-to-tail) ring P[graphic omitted], and is co-ordinated by a cyclo-octa- 1,5-diene molecule in a tub configuration. In both compounds the platinum atoms show essentially square-planar co-ordination.In a third complex the hexafluoroacetone forms part of a five-membered ring, in which it links the platinum and an olefin carbon atom of cycle-octa-1,5-diene. A similar complex, [P[graphic omitted]H(1,5-C8H12)], is a minor product from the reaction of [Pt(1,5-C8H12)2] with 1,1 -dicyano-2,2-bis(trifluroromethyl)ethylene. N-Methylhexafluoroisopropylideneamine and [Pt(1,5-C8H12)2] afford [P[graphic omitted]Me(1,5-C8H12)].

New mode of ‘benzyne’ co-ordination. Crystal and molecular structure of Os3(CO)9(PEt)(C6H4)

The benzyne ligand in Os3(CO)9(PEt)(C6H4) is shown by X-ray crystallography to be asymmetrically bound with one carbon atom σ-bonded to one osmium while a second bridges the two other metal atoms; a low energy process interchanges these two sites in solution.

A platinum-promoted ring-opening reaction of hexakistrifluoromethylbenzene involving carbon–carbon bond cleavage; crystal and molecular structure of bis(t-butyl isocyanide)platinacyclohepta-cis-2,cis-4,cis-6-triene

Reaction of hexakis(trifluoromethyl)benzene with triangulo-[Pt3(ButNC)6] or trans-stilbenebis(trimethyl-phosphine)platinum affords the metallacyclohepta-cis,cis,-cis-trienes [[grphic omitted](CF3)L2]; the bis(t-butylisocyanide) complex has been identified structurally by X-ray crystallography.

Reaction of hexafluorobut-2-yne with halogenodicarbonyl(η7-cycloheptatrienyl)-molybdenum complexes; crystal and molecular structure of [Mo2(µ-Cl)3(η7-C7H7)2]+[MoCl(CF3C2CF3)3]–

Reaction between the acetylene CF3C2CF3 and [MoX(CO)2(η7-C7H7)](X = Cl, Br, or I) affords dynamic ionic complexes [(η7-C7H7)Mo(µ-X)3Mo(η7-C7H7)]+[MoX(CF3C2CF3)3]–, the bridged trichloro-species being identified by single crystal X-ray diffraction studies.

The reaction of cyclopentadiene with dodecacarbonyltriruthenium: the isolation and crystal structure of tetracarbonylbis[dicarbonyl(η-cyclopentadienyl)ruthenio]ruthenium, [{Ru(η-C5H5)(CO)2}2Ru(CO)4]

The new title compound (1) has been isolated, in addition to the normal product [{Ru(η-C5H5)(CO)2}2](2) from the reaction of cyclopentadiene and [Ru3(CO)12] in refluxing heptane. Its formation, which may represent an early stage of the reaction of the diene with the triruthenium cluster, is enhanced by short reaction times and by a low relative concentration of cyclopentadiene. Crystals of (1) are monoclinic, space group P21/c, with Z= 2 in a unit cell of dimensions a= 6.819(3), b= 11.757(3), c= 13.085(5)A, and β= 110.84(2)°. The molecules are therefore centrosymmetric. The structure has been determined by heavy-atom methods from diffractometer data and refined to R 0.027 for 1 563 independent reflections. The three ruthenium atoms form a linear array [Ru–Ru 2.889(1)A] with the cyclopentadienyl rings in a mutually trans relationship on the terminal metal atoms. The central metal atom has four equatorial carbonyl groups, while the terminal metal atoms each carry two carbonyl groups which are eclipsed relative to those on the central atom. The metal–carbonyl distances on the central atom are significantly longer than those on the terminal atoms.

Reactions of low-valent metal complexes with fluorocarbons. Part 33. Bis(cyclo-octa-1,5-diene)platinum with hexafluorobut-2-yne; crystal and molecular structures of bis(cyclo-octa-1,5-diene)tetrakis(hexafluorobut-2-yne)triplatinum and bis(cyclo-octa-1,5-diene)bis(hexafluorobut-2-yne)diplatinum

Reaction of [Pt(cod)2](cod = 1,5-C8H12) with hexafluorobut-2-yne (hfb) affords [[graphic omitted](CF3)}(cod)], which reacts with triphenylphosphine, carbon monoxide, or hexafluorobut-2-yne to afford [[graphic omitted](CF3)}(PPh3)2], [[graphic omitted](CF3)}(CO)2(cod)], and [[graphic omitted](CF3)}(cod)2] containing three-, four-, six-, and eight-membered rings. The triplatinum species has been structurally identified by X-ray crystallography. The crystals are orthorhombic, space group Pbca, Z= 8 in a unit cell of dimensions a= 16.513(10), b= 28.536(30), and c= 15.429(8)A. This complex Is also the major product in the reaction of [Pt(C2H4)3] with hfb in the presence of cod. A minor product in this reaction, [[graphic omitted](CF3)}(cod)2], is formed in high yleld on treatment of [[graphic omitted](cod)2] with hfb. A crystal-structure determination has established the presence in this molecule of a six-membered ring containing two platinum atoms. Crystals are triclinic, space group PZ= 2 in a unit cell of dimensions a= 11.099(5),b= 9,413(2), and c= 14.317 (4)A, α= 110.72(2), β= 93.50(3), and γ= 113 08(3)°.