Kwok W. Chiu

Interaction of organic azides with methyl compounds of cobalt, rhodium, iridium, ruthenium and zirconium to give azido or 1,3-triazenido complexes. The crystal structures of tris-trimethylphosphineazido-dimethylcobalt(III) and bis(carbonyl)trimethylphosphineazidocobalt(I)

Abstract The interaction of azidotrimethylsilane with mer-CoMe3(PMe3)3, fac-RhMe3(PMe3)3, fac-IrMe3(PMe2Ph)3, cis-RuMe2(PMe3)4 and (η5-C5H5)2ZrMe2 gives tetramethylsilane and, respectively, the azido compounds MMe2(N3)(PMe3)3, M = Co, Rh, IrMe2(N3)(PMe2Ph)3, cis-Ru(N3)2(PMe3)4 and (η5-C5H5)2ZrMe(N3). The crystal structures of CoMe2(N3)(PMe3)3 and of the derived complex Co(N3(CO)2(PMe3)2 have been determined by X-ray diffraction. The dimethyl cobalt(III) compound has an octahedral structure with a mer arrangement of the three PMe3 groups. The CoIII-N distance is rather long, at 2.071(4) A. The cobalt(I) carbonyl compound has a trigonal bypyramidal structure with the two phosphines occupying the axial sites. The CoI-N distance is 2.03(1) A. The interaction of PhN3 with (η5-C5H5)2ZrR2, R = Me, Ph, gives the 1,3-triazenido complexes (η5-C5H5)2ZrR(RNNNPh) while mer-CoMe3(PMe3)3 and p-MeC6H4N3 react to give CoMe2(MeNNNp-tol)(PMe3)2. In all three cases the triazenido group appears to be bidentate.

Reactions of phenylimidotrichlorobis(triphenyl-phosphine)rhenium(V). Reaction with trimethyl-phosphine and reduction of trimethylphosphine complex to phenylamido complexes of rhenium(I, III). The X-ray crystal structures of phenylamido-(dinitrogen)tetrakis(trimethylphosphine)-rhenium(I) and phenylamido(buta-1,3-diene)-tetrakis-(trimethylphosphine)rhenium(I)

Abstract The interaction of Re(NPh)Cl3(PPh3)2 with PMe3 gives Re(NPh)Cl3(PMe3)(PPh3) or Re(NPh)Cl3(PMe3)2 depending on conditions. In the presence of excess PMe3 the phenylimido compounds in tetrahydrofuran are reduced by sodium amalgam giving products whose nature depends on the atmosphere (Ar, N2, H2 CO, butadiene) used. The following compounds have been characterised: Re(NHPh)(N2)(PMe3)4, ReH(NHPh)(η′-CH2PMe2)(PMe3)4, Re(H)2(NHPh)(PMe3)4, Re(NHPh)(CO)2(PMe3)3, Re(NHPh)(CO)3(PMe3)2, Re(NHPh)(η4-C4H6)(PMe3)3 and Re(NPh)Cl2(PMe3)3. The structures of Re(NHPh)(N2)(PMe3)4 (3) and Re(NHPh)(C4H6)(PMe3)3, (8) have been confirmed by single-crystal X-ray diffraction studies. (3) is monoclinic, space group P21/n with a = 9.574(2), b = 19.528(3), c = 14.385(3)A and β = 99.06(2)°; (8) is orthorhombic, space group Pbc21, with a = 12.207(2), b = 13.884(2), c = 14.242(2)A. The structures were solved via the heavy atom method and refined by least squares to R values of 0.065 and 0.062 for 3249 and 2009 observed diffractometer data, respectively. In the dinitrogen complex the N2 and NHPh ligands adopt a cis configuration with ReN bond lengths of 1.955(13) and 2.200(14)A, respectively. In the butadiene complex, whose structure is not well defined due to disorder and/or pseudo symmetry correlation effects, the ReN (amido) distance is 2.13(3)A.

Interaction of t-butyl isocyanide with methyl compounds of tungsten, rhenium, zirconium, titanium, and tantalum. The X-ray crystal structures of W–N(But)CMe2(Me)(NBut)[N(But)CMeCMe2] and its hydrogen chloride adduct. t-Butyl isocyanide complexes of molybdenum(0), ruthenium(II), and rhodium(I)

The interaction of t-butyl isocyanide with the following methyl compounds leads to the formation of insertion products in which methyl groups are transferred to the isocyanide ligand: hexamethyltungsten, hexamethylrhenium, tetraneopentylzirconium, bis(η-cyclopentadienyl)dimethyltitanium, and dichlorotrimethyltantalum. For WMe6, a unique transfer of five methyl groups occurs to give the complex [graphic omitted]Me2(Me)(NBut)[N(But)CMeCMe2](1) whose structure has been determined by X-ray crystallography. Crystals of (1) are triclinic, space group P, with a= 8.829(2), b= 10.265(1), c= 14.324(5)A, α= 90.87(2), β= 101.47(2), γ= 82.44(2)°, and Z= 2. The structure was solved by the heavy-atom method and refined to R= 0.057 for 4 069 observed [l > 1.5σ(l)] diffractometer data. The W–N and W–C bond lengths in the azatungstacyclopropane unit are 1.91(1) and 2.20(1)A, the W–C(Me) distance is 2.10(1)A, and the remaining W–N distances are 1.76(1)A to the t-butylamide, and 1.94(1)A to the alkylalkeneamide. All W–N bonds are presumed to be strengthened by π-bonding. The complex (1) reacts with three mol of hydrogen chloride to give the salt (2) whose structure has also been determined by X-ray methods and shown to be [Me2CC(Me)NH2But][[graphic omitted]Me2(Me)(NBut)Cl3]. Crystals of (2) are also triclinic, space group P, with a= 11.178(2), b= 12.730(2), c= 12.155(2)A, α= 84.21 (2), β= 111.31 (2), γ= 97.59(2)°, and Z= 2. The structure was solved by the heavy-atom method and refined to R= 0.077 for 4 559 observed data. The identification of the components of the structure was complicated by disorder. The main points of interest in the structure are the protonation of the N atom of the azatungstacyclopropane ring leading to an increase in the W–N bond length in the ligand and the shortening of the ButN(1)→W bond relative to that in compound (1). The t-butyl isocyanide complexes Mo(CNBut)6, RuH2(PMe3)2(CNBut)2, and RhMe(CnBut)4 were also synthesised. Infrared and 1H, 13C, and 31P n.m.r. spectra of the compounds are reported.

t-Butyl isocyanide complexes of rhenium(I), chromium(O), tungsten(O,I) and platinum(II); X-ray crystal structures of bis(t-butylisocyanide)- tris(trimethylphosphine)chlororhenium(I) and tris(t-butylisocyanide)bis(trimethyl- phosphine)chlororhenium(I)

Abstract The reduction of ReCl 4 (THF) 2 in the presence of excess t -butylisocyanide by sodium amalgam produces pentakis ( t -butylisocyanide)chlororhenium(I), which has been converted to the corresponding methyl and ethyl derivatives. The reaction of pentakis(trimethylphosphine)chlororhenium(I) with Bu t NC gives partially substituted complexes, ReCl(CNBu t ) 2 (PMe 3 ) 3 and ReCl(CNBu t ) 3 (PMe 3 ) 2 . The structures of both compounds have been determined by X-ray methods. Octahedral ReCl(CNBu t ) 2 (PMe 3 ) 3 has trans isocyanide groups with one linear [C N C = 175(1)°] and one slightly bent [C N C = 159(1)°]. The Re C bond lengths are equal within experimental error [2.004(7), 2.003(7)A]. In the octahedral ReCl(CNBu t ) 3 (PMe 3 ) 2 , for which the structure is not well defined, due to disorder, the unique isocyanide trans to chlorine is considerably bent at the nitrogen atom [C Nˆ C = 141(6)°] and appears to show the shortest Re C bond length, 1.94(5) vs 2.02(5)Afor the other two isocyanides which are mutually trans . Protonation of these two isocyanide complexes with fluoroboric acid gives, respectively, the salts [ReCl(CNBu t )CNHBu t (PMe 3 ) 3 ]BF 4 and [ReCl(CNBu t ) 2 CNHBu t (PMe 3 ) 2 ]BF 4 , whose configurations have been determined by NMR spectroscopy. The reduction by sodium amalgam of Cr 2 (CO 2 Me) 4 in tetrahydrofuran in presence of Bu t NC gives a high yield of Cr(CNBu t ) 6 while similar reduction of the dimeric tungsten(II) complex of the anion (mhp) of 2-methyl-6- hydroxypyridine gives W(CNBu t ) 6 . Interaction of W 2 (mhp) 4 in methanol-ether with Bu t NC gives a tungsten(I) complex W 2 (η-mhp) 2 (Bu t NC) 4 , which may be an intermediate in the reductive cleavage reaction. Interaction of cis -PtMe 2 (PMe 3 ) 2 with Bu t NC leads only to replacement of one PMe 3 group to give the complex cis -PtMe 2 (PMe 3 )(CNBu t ).

Bis(dimethylphosphino)methane complexes of iron and ruthenium

Abstract The interaction of iron(II) acetate in presence of bis(dimethylphosphino)methane (dmpm) with dimethyl- and diethylmagnesium leads to cis-FeMe2(

Electrophilic attack on the [µ3-acetyl-C1(Fe1 : Fe2)O(Fe1 : Fe3)]nonacarbonyl-triangulo-triferrate(1–) anion by fluoroboric acid and methyl fluorosulphate. Carbon–oxygen bond cleavage to give µ3-ethylidyne and µ-methoxo-groups. X-Ray crystal structures of Fe3(CO)9(µ3-MeCO)(µ-H), Fe3(CO)9(µ3-CMe)(µ3-OMe), and Fe3(CO)9(µ3-CMe)(µ3-COMe)

The (µ3-acetyl)-nonacarbonyltriferrate(1–) ion, [Fe3(CO)9(µ3-MeCO)]–, reacts with fluoroboric acid to give the neutral clusters Fe3(CO)9(µ3-MeCO)(µ-H)(1), Fe3(CO)10(µ-CMe)(µ-H)(2), and in small yield, Fe3(CO)9(µ3-MeCOH)(3). With methyl fluorosulphate the anion reacts to give either Fe3(CO)9(µ3-CMe)(µ3-OMe)(4) or Fe3(CO)9(µ3-CMe)(µ3-COMe)(5), depending upon the reaction conditions. The crystal structures of (1), (4), and (5) have been determined by X-ray diffraction studies. Mechanisms for the electrophilic attacks and for the C–O bond cleavage of the µ3-acetyl group are discussed.

Synthesis and reactions of phenylimidotrimethyl-bis(trimethylphosphine)-rhenium(V). Synthesis and X-ray crystal structure of bis(trimethylsilylmethyl)oxo-rhenium(V)-μ-oxo-tetrakis(trimethylphosphine)rhenium (I)-(trimethylsilylmethyl)dioxorhenium(V), (ReRe)

Abstract The interaction of phenylimidotrichloro bis(trimethylphosphine) with dimethylmagnesium gives the trimethyl compound, Re(NPh)Me3(PMe3)2. Exchange reactions between the trichloro and trimethyl compounds are studied by 1H nuclear magnetic resonance and the intermediates Re(NPh)Me2Cl(PMe3)2 and Re(NPh)MeCl2(PMe3)2 isolated. The trimethyl reacts with fluoroboric acid to give a phenylamido complex [Re(NHPh)Me2F(PMe3)2]BF4, with acetic acid to give Re(NPh)Me(CO2Me3)2, and with trityltetrafluoroborate to give [Re(NPh)Me2(PMe3)2]BF4. The interaction of Re(NPh)Cl3(PMe3)2 with excess of bis(trimethylsilylmethyl)magnesium and of trimethyl-phosphine in tetrahydrofuran gives an unusual tri-rhenium compound, (Me3SiCH2)3(O)Re-μ-O-Re(PMe3)4Re(O)2(CH2SiMe3) whose structure as a thf solvate, has been determined by X-ray crystallography. Crystals of the latter are monoclinic, space group P21/n with a = 15.512(3), b = 15.392(2), c = 21.506(4) A, β = 100.19(2)°, Z = 4. The structure has been refined to an R of 0.07 for 5028 observed diffractometer data. The molecule is tri-nuclear with the central rhenium carrying four PMe3 groups being bound to the second rhenium by a short ReRe bond and to the third by an asymmetric oxygen bridge. The end rhenium bound to the bridge oxygen carries two CH2SiMe3 groups and an oxygen atom, while the other has one CH2SiMe3 group and two oxygen atoms.

Alkyl complexes of palladium (II) with trimethylphosphine and 1,2-bis(dimethylphosphino) ethane ligands

Abstract A number of neutral, mononuclear dialkylpalladium(II) tertiary phosphine complexes of geneal formula cis or trans -PdR 2 (PMe 3 ) 2 and cis -PdR 2 (dmpe) [dmpe = 1,2-bis(dimethylphosphino)ethane], R = Me, CH 2 Ph, CH 2 CMe 2 Ph, CH 2 SiMe 3 have been obtained by interaction of magnesium reagents with palladium(II) acetate or trans -Pd(O 2 CMe) 2 (PMe 3 ) 2 .

Bis(dimethylphosphino)methane (dmpm) complexes of iron, molybdenum and chromium: X-ray crystal structures of FeCr(CO)6(μ-dmpm)2 and Fe2(CO)4(μ-CO)(μ-dmpm)2

Abstract The photolysis of Fe(η1-dmpm)(dmpm)2 [dmpm = bis(dimethylphosphino) methane) with Cr(CO)6 and Fe(CO)5 under UV irradiation produces FeCr(CO)6(μ-dmpm)2, Fe2(CO)6(μ-CO)(μ-dmpm) and Fe2(CO)4(μ-CO)(μ-dmpm)2 respectively. The interaction of Mo(CO)3(MeCN)3 and (C7H8)Cr(CO)3 with dmpm produces Mo2(CO)6(μ-dmpm)3 and cis-Cr(CO)2(dmpm)2 respectively. The X-ray crystal structure of FeCr(CO)6(μ-dmpm)2 shows the molecule to contain a trigonal bipyramidal Fe(CO)3P2 unit plus a square pyramidal Cr(CO)3P2 unit held closely together by the methylene bridges of the dmpm ligands with steric compression between the CO groups causing distortions from ideal geometry in each case. The Cr … Fe distance is 3.111(6) A and there seems to be little structural evidence of any form of interaction between the 16e Cr(O) centre and the Fe-containing unit. The structure of Fe2(CO)4(μ-CO)(μ-dmpm)2 contains a symmetrical μ2-carbonyl and a single bond between the two symmetry related (m) iron atoms. The Fe … Fe distance is 2.719(4) A.

Chemistry of metallacyclobutanones. Part 4. The synthesis of 1,3-diphenyl-substituted oxodimethylenemethane complexes of platinum(II) and palladium(II)via the dianion [PhCHC(O)CHPh]2–, and the X-ray crystal structure of [Pt{η3-CHPhC(O)CHPh}(AsPh3)2]·2CH2Cl2

Treatment of the complexes cis-[PtCl2L2] or trans-[PdCl2L2] with the organopotassium reagent K2[PhCHC(O)CHPh] in tetrahydrofuran affords the η3-oxodimethylenemethane (puckered metallacyclobutan-3-one) complexes [M{η3-CHPhC(O)CHPh}L2](M = Pt, L = AsPh3 or PPh3; L2= cyclo-octa-1,5-diene (cod); M = Pd, L = PPh3 or PEt3). X-Ray data indicate that these complexes contain highly non-planar metal–oxodimethylenemethane systems with both phenyl substituents adopting equatorial positions. In the synthesis of [Pt{η3-CHPhC(O)CHPh}(PPh3)2] a small amount of a trans diphenyl-substituted isomer is formed, along with the principal cis diequatorial isomer. N.m.r. data for the oxodimethylenemethane complexes are reported.