Graeme Douglas

Metal-promoted alkyne trimerisation leading to novel metallacycles. The molecular structures of [Mo{η3-C(CF3)C(CF3)C(Me)C(Ph)SPri}(CF3CCCF3)(η5-C5H5)], [WSPri{η5-C(CF3)C(CF3)C(CF3)C(CF3)C(Me)C(Ph)}(η5-C5H5)], and [W(SC6H4Me-4){η4-C(CF3)C(CF3)C(CO2Me)C(CO2Me)C(CF3)C(CF3)}(η5-C5H5)]

Addition of alkynes to isomeric η2-C,C-vinyl [M{η3-C(CF3)C(CF3)SR′}(CF3CCCF3)(η5-C5H5)](M = Mo, W; R′= Pri) and bis-alkyne complexes [MSR′(CF3CCCF3)2(η5- C5H5)](M = W, R′= 4-MeC6H4) gives new metallacycles formed by linking of two or three alkynes; X-ray analyses reveal two modes of bonding for the tris alkyne (CR)6 ligands.

Synthetic, spectroscopic and structural studies of metallacyclopentadiene complexes of tungsten; the crystal structure of [WC(CF3)C(CF3)C(CF3)C(CF3)(SPri)-(4-MeC6H4NC)2(η5-C5H5)]

Abstract Reactions of the η2-vinyl complex [W {η3-C(CF3)C(CF3)SPri}(CF3CCCF3)(η5C5H5)] with isocyanides RNC give metallacyclopentadiene derivatives [ WC(CF 3 )C(CF 3 )C(CF 3 )C (CF3)(SPri)(CNR)2 (η5-C5H5)] (R = Me, Ph or 4-MeC6H4) via coordinatively unsaturated intermediates [ WC(CF 3 )C(CF 3 )C(CF 3 )C (CF3)(SPri)(CNR)(η5-C5H5)] isolated and characterised in the case R = 4-MeC6H4. The crystal structure of the d2 complex [ WC(CF 3 )C(CF 3 )C(CF 3 )C (CF3)(SPri)-4-MeC6H4NC)2(η5-C5H5)] has been determined by X-ray methods. The WC4(CF3)4 ring system is approximately planar, with single WC bonds, mean length 2.210(4) A, and localised CC double bonds.

Synthesis and characterization of complexes with Pt3(µ3-SnX3) groups including the first SnF3– complex; possible models for heterogeneous Pt–Sn catalysts

Novel complexes containing Pt3(µ3-SnX3) groups have been prepared by reaction of [Pt3(µ3-CO)(µ-dppm)3][PF6]2(dpmm = Ph2PCH2PPh2) with organotin hydrides or with SnX3– and are of intrest as possible models for heterogeneous Pt–Sn/support catalysts; the structures of [Pt3{µ3-SnMe2(PO2F2)}(µ-dppm)3]+ and disordered {[Pt3(µ3-SnF3)(µ3-CO)(µ-dppm)3][PF6]}0.75[Pt3(µ3-SnF3)(µ3-Cl)(µ-dppm)3]0.25 are determined, the latter being the first SnF3– complex to be crystallographically characterized.

A fluxional tetraplatinum cluster: solution and solid state structure of the cation [Pt4(µ-H)(µ-CO)2(µ-Ph2PCH2PPh2)3(Ph2PCH2PPh2)]+

The 58-electron cationic cluster complex [Pt4(µ-H)(µ-CO)2(µ-dppm)3(dppm-P)]+, dppm = Ph2PCH2PPh2, has been characterized in solution by n.m.r. spectroscopy and in the solid by X-ray analysis of the PF6– salt; the cation displays novel fluxionality with rapid rotation of a µ-H below and a µ-Pt(CO)2(dppm-P) unit above a Pt3(µ-dppm)3+ triangle.

Mechanisms of alkyne trimerisation at molybdenum and tungsten centres leading to novel metallacycles: crystal and molecular structures of two isomeric forms of [Mo{C(CF3)C(CF3)C(CF3)C(CF3)C(CO2Me)C(CO2Me)(SPri)}(η5-C5H5)]

The η2-C,C vinyl complexes [M{η3-C(CF3)C(CF3)SR}(CF3CCCF3)(η5-C5H5)]1(M = Mo, R = Pri; M = W, R = Me, Et or Pri) reacted with dimethyl acetylenedicarboxylate R′CCR′(R′= CO2Me) to give products of alkyne trimerisation containing two different oligomerisation sequences depending on whether R′CCR′ occupies a terminal or central position in the alkyne trimer chain, i.e. C(CF3)C(CF3)C(CF3)C(CF3)C(R′)C(R′) and C(CF3)C(CF3)C(R′)C(R′)C(CF3)C(CF3). With M = Mo, kinetic 19F NMR studies established a reaction sequence proceeding above ca.–30 °C via two different butadienyl complexes [M{η2-C(CF3)C(CF3)C(R′)C(R′)SPri}(CF3CCCF3)(η5-C5H5)]2 and 3 to give isomeric trienyl derivatives [Mo{η6-C(CF3)C(CF3)C(CF3)C(CF3)C(R′)C(R′)SPri}(η5-C5H5)]4 and [Mo{η5-C(CF3)C(CF3)C(CF3)C(CF3)C(R′)SPriC(R′)}(η5-C5H5)]5 which were isolated at room temperature. X-Ray diffraction studies established that in each case the trienyl ligand is bound to the metal via an η2-C,C alkenyl linkage, and two σ carbon–metal bonds. In 4 this is accompanied by co-ordination of a CO unit of a carbomethoxy carbonyl whereas in 5 the thiolate sulfur is bonded to the metal. Above room temperature 5 isomerises to give species 6 and ultimately 7 which appears to result from thiolate transfer to the metal to give a seven-membered metallacycle. With M = W, the reactions also proceed via a butadienyl complex 2 but this isomerises via two other intermediates to give trienyl products [W{η6-C(CF3)C(CF3)C(R′)C(R′)C(CF3)C(CF3)SR}(η5-C5H5)] and [WF{η5-C(CF2)C(CF3)C(R′)C(R′)C(CF3)C(CF3)SR}(η5-C5H5)]. X-Ray diffraction studies established that the trienyl ligand in the former is co-ordinated via one σ, two π alkene linkages and a thiolate sulfur. Two isomeric forms were structurally characterised which differ only in the orientation of the thiolate isopropyl substituent which can adopt syn or anti positions. In the fluoride a CF3 fluorine has been transferred to the metal and this has generated a hexatrienyl attachment via a quasi π-allylic interaction and through W–C and W–S σ bonds.

The mechanism of isomerisation of the CC bond in ethenethiolato ligands co-ordinated to molybdenum and tungsten. The molecular structures of (E)-exo-[W{η3-SC(CF3)C(CF3)H}(CF3CCCF3)(η5-C5H5)] and (Z)-endo-[W{η3-SC(CF3)C(CF3)H}(CF3CCCF3)(η5-C5H5)]

Thermolysis of the η2-vinyl complex [W{η3-C(CF3)C(CF3)SBut}(CF3CCCF3)(η5-C5H5)] gives the η3-ethenethiolato derivative (E)-exo-[W{η3-SC(CF3)C(CF3)H}(CF3CCCF3)(η5-C5H5)], which undergoes concomitant exo→endo and E→Z isomerisation to give (Z)-endo-[W{η3-SC(CF3)C(CF3)H}(CF3CCCF3)(η5-C5H5)], thus providing evidence for a ring-flip mechanism in metal-promoted alkene isomerisations.

Synthesis and reactions of tungsten(II) norbornadiene (nbd) complexes. The crystal and molecular structure of [WBr(SC6F5)(CO)2(nbd)]

The reaction of [WBr2(CO)2(nbd)]1(nbd norbornadiene) with TI(C5H5) gave a monocarbonyl derivative [WBr(CO)(nbd)(η5-C5H5)]2. With TI(O2CMe) and TI[O(S)CMe]. complex 1 gave monosubstituted derivatives[WBr(O2CMe)(CO)2(nbd)]3a and [WBr{O(S)CMe}(CO)2(nbd)]3b which appear to be seven-co-ordinate according to IR data. In contrast 1 and TI(SC6F5)(1:1 molar ratio) gave the six-co-ordinate complex [WBr(SC6F5)(CO)2(nbd)]4. An X-ray diffraction study of 4 established that it has a distorted-octahedral structure with trans W–CO bonds approximately perpendicular to a plane containing the W. Br and S atoms and the midpoints of the nbd CC bonds. Simple electronic arguments provide a rationalisation of many of the structural features of 4. Reaction of 1 with 2 molar equivalents of TI(SC6F5) gave the bis(thiolate) derivative [W(SC6F5)2(CO)2(nbd)]5 again with a trans arrangement of CO ligands. The reactions of 5 with L =PEt3. PMe2Ph or P(OMe)3 gave the six-co-ordinate complexes [W(SC6F5)2(CO)2L2]6 which exist in two isomeric forms, red or green. Dynamic NMR studies have been used to characterise the isomeric behaviour and fluxional processes in the complexes.

Synthesis of sulphimide complexes of palladium and platinum. Crystal and molecular structure of cis-dichloro[S,S-dimethyl-N-(2-pyrimidinyl)sulphimide](triphenyiphosphine)pailadium(II)

Reactions of [MCl2(PhCN)2](M = Pd or Pt) and K2[PtCl4] with S,S-dimethyl-N-heteroaromatic sulphimides Me2SNR (R = 2-pyridyl, 4-methyl-2-pyridyl, 2-pyrimidinyl, 4-methyl-2-pyrimidinyl, or 2-pyrazinyl) give 1 : 1 adducts trans-[M2Cl2(µ-Cl)2(Me2SNR)2](1) in which the sulphimide appears to co-ordinate through the ylide nitrogen according to 1H n.m.r. studies. Reaction of [MCl2(PhCN)2] with Me2SNPh gives a bis(sulphimide) complex trans-[MCl2(Me2NSPh)2](2) when M = Pd but when M = Pt a phenylnitrene derivative cis-[PtCl2(Me2SNPh)(NPh)](3) is obtained. Reactions of complexes (1) with phosphines L = PEt3, PMe2Ph, PMePh2, or PPh3, give 1 : 1 adducts [MCl2L(Me2SNR)][M = Pd; R = 2-pyridyl, L = PEt3, PMe2Ph, PMePh2, or PPh3, (4a)–(4d); M = Pt, R = 2-pyridyl, L = PEt3(4e); M = Pd, R = 2-pyrimidinyl, L = PPh3(4f)]. An X-ray analysis of cis-[PdCl2(PPh3)(Me2SNC4H3N2)]·CH2Cl2(4f) revealed that the pyrimidine rather than the sulphimide N atom is the point of attachment of the sulphimide ligand to Pd. Conformational energy calculations suggest that electronic rather than steric factors determine which N atom acts as donor to Pd. The crystals are monoclinic, space group P21/n, with a= 17.307(6), b= 9.182(1), c= 17.960(2)A, β= 97.15(2)°, R= 0.024 for 1 999 independent reflections with I > 3σ(I). N.m.r. studies suggest a trans structure for complex (4e) with sulphimide co-ordination via the pyridyl nitrogen. The isomerism and fluxional behaviour of (4c) and (4d) was studied by variable-temperature n.m.r. spectroscopy.