Domenico C. Cupertino

Preparation and purification of metal alkyls for use in the MOCVD growth of II/VI compound semiconductors

Abstract The preparation of adducts of Me 2 Cd and Me 2 Zn with a range of nitrogen donor ligands has been investigated. Those with two nitrogen atoms, which cannot for geometrical reasons bind to the same metal atom, are shown to give involatile polymeric adducts, which dissociate on heating at one atmosphere or in vacuo below the sublimation temperature of the adduct or the Lewis Base. These adducts may be suitable for the purification of Me 2 Cd or Me 2 Zn. Those that dissociate Me 2 Zn or Me 2 Cd below the melting point of the adduct may be suitable precursors for the delivery of these alkyls by the MEM method. A new preparation of Et 2 Te based on the two phase reactions of aqueous Na 2 Te with EtBr is also reported. This gives high yields of Et 2 Te which is polytellurium-free.

Synthesis of cobalt(II) complexes of derivatised salicylaldoxime ligands; X-ray crystal structures of DMSO adducts of bis(3-nitro-5-methylsalicylaldoximato)cobalt(II) and bis(3-nitro-5-phenylsalicylaldoximato)cobalt(II)

Abstract A total of five salicylaldoxime ligands, (HL1–5), analogues of commercial metal extractants were synthesised and characterised. The cobalt(II) complexes [CoL2] (L=L1–5) of these ligands were synthesised and characterised by microanalysis, atomic absorption, infra and mass spectroscopy. X-ray structure analysis was carried out on the adducts [Co(L)2(dmso)2] (L=L4,5). These are the only structurally characterised cobalt salicylaldoxime complexes apart from three five-coordinate nitroso complexes [CoL2(NO)] reported in the 1980s (J. Crystallogr. Spectrosc. Res. 13 (1983) 413; J. Crystallogr. Spectrosc. Res. 16 (1986) 6). The structures of the two adducts characterised show octahedral coordination with two dmso molecules occupying axial positions and two salicylaldoxime units in each molecule occupying equatorial positions. The introduction of nitro groups on the two ligands has been found to stabilise oxidation (II) in preference to (III) in both cobalt complexes. These groups were found to have what appears to be a significant contribution to intra-ligand hydrogen bonding resulting in three-centre H bonds on either side of the molecules, which in turn adopt unusual chair conformations.

Diazopyrazolones as weak solvent extractants for copper from ammonia leach solutions

Potentially bidentate 4-diazopyrazol-5-one ligands carrying a range of substituents can readily be prepared by coupling arene diazonium salts on to the appropriate pyrazolones. Hydrocarbon-soluble versions are shown to be suitable reagents for the recovery of copper by solvent extraction from ammoniacal leach solutions, and potentially have greater resistance to chemical degradation than the β-diketones which have been used. Cobalt(III), nickel(II), copper(II) and zinc(II) complexes with 4-(4-tert-butylphenylazo)-3-methyl-1-phenyl-5-pyrazolone (HL) have been characterised by X-ray crystallography. The significant deviations from planar coordination geometry which are observed in [CuL2] and [CuL′2], where HL′ is 3-methyl-1-phenyl-4-phenylazo-5-pyrazolone, arise from interligand repulsion, and account for the relatively weak complexation and ease of stripping of copper from this class of extractant. The cobalt(III) complex [CoL3]·3MeOH and the high spin nickel(II) complex [NiL2(MeOH)2]·2MeOH both have approximately octahedral geometries, but show significantly different bite distances in the chelate rings. The zinc complex [ZnL2] has a pseudo-tetrahedral structure.

Camphor-derived β-ketophosphine complexes of rhodium(III) and iridium(III); x-ray crystal structure of cis,mer-trichlorobis[(1R)-endo-(+)-3-diphenylphosphinocamphor]rhodium(III) chloroform()

Reaction of (1 R )- endo -(+)-3-diphenylphosphinocamphor (L) with RhCl 3 ·3H 2 O in ethanol gives trans,mer -[RhCl 3 L 2 ] and in THF gives cis,mer -[RhCl 3 L 2 ]. L reacts with IrCl 3 ·3H 2 O to give trans,mer -[IrCl 3 L 2 ]. On reaction with excess AgBF 4 , trans,mer -[IrCl 3 L 2 ] gives cis,trans -[IrCl 2 L 2 ]BF 4 . The complexes were characterized by IR, 1H and 31 P NMR spectroscopy. Trans,mer -[MCl 3 L 2 ] (M = Rh or Ir) and cis,mer -[RhCl 3 L 2 ] show both unidentate and bidentate binding of L (through phosphorus and carbonyl oxygen atoms) and cis,trans -[IrCl 2 L 2 ]BF 4 , shows only bidentate binding. The compound cis,mer -[RhCl 3 L 2 ] has been characterized crystallographically. The complex is a distorted octahedron about rhodium with the three chloride ligands having meridional geometry, and the ligand phosphorus atoms being cis to one another. The RhP bond length for the bidentate ligand is 2.339(6) A and for the unidentate ligand is 2.268(6) A. The bite angle for the bidentate ligand is 81.8(4)°.

Camphor-derived β-ketophosphine complexes of palladium(II) and platinum(II)

Reaction of chlorodiphenylphosphine with the lithium enolate derived from the treatment of (1R)-endo-(+)-3-bromocamphor (camphor = bornan-2-one) with n-butyl-lithium gives (1R)-endo-(+)-3-diphenylphosphinocamphor (L). This new chiral β-ketophosphine ligand reacts with [Pd(CH3CN)2Cl2] to give trans-[PdL2Cl2], and in a 1 : 1 ratio to give the chloro-bridged dimer [{PdL(µ-Cl)Cl}2]. The ligand L reacts with [Pt(CH3CN)2Cl2] to give trans-[PtL2Cl2]. Thermolysis of [ML2Cl2](M = Pd or Pt) in refluxing xylene gives mixed phosphine–phosphinite complexes with mutually cis chlorides. The complex [PdL2Cl2] reacts with an excess of AgBF4 to give [PdL2][BF4]2 which is shown to contain bidentate binding through the phosphorus and keto-oxygen atoms. All complexes are characterised by i.r., 1H and 31P n.m.r. spectroscopy.

Camphor-derived β-ketophosphonate complexes of molybdenum (VI) and titanium (IV); crystal and molecular structure of dichloro [(1R)-endo-(+)-3-(diethoxyphosphoryl)camphor]dioxomolybdenum(VI)

Reaction of (1R)-endo-(+)-3-(diethoxyphosphoryl)camphor (L) with MoO2Cl2 gives [MoO2Cl2L] with cis oxygen and trans chloro ligands if the stoicheiometry is 1 : 1 whilst 2 equivalents of L give [MoO2Cl2L2]. On reaction with 1 equivalent of L, TiCl4 gives [TiCl4L]. The complexes were characterised by i.r., 1H, and 31P n.m.r. spectroscopy, and shown to contain bidentate binding (through the phosphoryl and carbonyl oxygen atoms) except for [MoO2Cl2L2], where binding is only through the phosphoryl oxygen. The compound [MoO2Cl2L] has been characterised crystallographically. Crystals are orthorhombic (space group P212121) with a= 15.528(2), b= 13.721(2), c= 9.777(1)A, and Z= 4. The structure was obtained from 1 664 observed intensities measured on a diffractometer and refined to an R value of 0.043. The complex is distorted octahedral about molybdenum with mutually cis oxygen atoms and mutually trans chlorine atoms although the O–Mo–O angle is 102.8 (5)° and the Cl–Mo–Cl angle is only 158.0(1)°. The organic ligand is bound through the phosphoryl and carbonyl oxygen atoms and the geometry of the ligand is little distorted from that of e.g. 3-bromocamphor. The bite angle for the bidentate ligand is 78.6 (3)° and the Mo–O (phosphoryl) bond length [2.183(7)A] is significantly shorter than to the cabonyl oxygen [2.402(7)A]. The known absolute configurations of the chiral centres have been confirmed as (1R), (3S), and (4S).

A high activity molybdenum containing epoxidation catalyst and its use in regioselective epoxidation of polybutadiene

MoO2CI2[3-(diethoxyphosphinyl)camphor] is a highly active catalyst for the epoxidation of alkenes by ButOOH; for polybutadiene containing cis-1,4-trans-1,4-, and 1,2-polymerised units, very high selectivity to the backbone double bonds is observed.

Co-ordination of highly substituted alkenes to transition-metal complexes: preparation and crystal and molecular structures of the complexes [{RhCl(Ph2PO2CCHCMe2)}2] and [{RhCl(Ph2PO2CCHCHCHCHMe)}2]

Reaction of Ph2PCl with RR′CCR″C(X)OH in the presence of triethylamine produces Ph2POC(X)CR″CRR′(X = O; R = R′= Me, R″= H; R = R″= H, R′= Me; R = R″= H, R′= CHCHMe; R = Ph, R′= H, R″= Me; X = H2, R = R′= Me, R″= H) in high yield. These ligands react with [(RhClL2)2](L = C2H4 or cyclo-octene) to give high yields of [{RhCl(Ph2POC(X)CR″CRR′)}2] in which the ligands are bound through phosphorus and the double bond. The new compounds have been fully characterised by spectroscopic means, as well as by the crystal structures of [{RhCl(Ph2PO2CCHCMe2)}2] and [{RhCl(Ph2PO2CCHCHCHCH-Me)}2]. Crystal data: for [{RhCl(Ph2PO2CCHCMe2)}2], monoclinic, a= 8.485(1), b= 28.070(3), c= 14.253(1)A, β= 93.96(1)°, space group P21/n; for [{RhCl(Ph2PO2CCHCHCHCHMe)}2], monoclinic, a= 17.372(2), b= 22.070(1), c= 9.986(2)A, β= 104.51(1)°, space group P21/a. Both complexes contain dimeric structures with bridging chlorine atoms. Each rhodium atom is in an approximately square-planar configuration, and is bonded to two chlorine, one phosphorus atom, and one π-bonded CC double bond, the phosphorus and π system being part of a chelate ring structure. In [{RhCl(Ph2PO2CCHCHCHCHMe)}2] the α,β unsaturated linkage is bonded to the rhodium only, the γ,δ double bond being free.

Linkage isomerism in rhodium(I) complexes of mixed anhydrides of diphenylphosphinous and acrylic acids: crystal and molecular structure of [RhCl(PPh3)(Ph2PO2CCHCHMe)]

Reactions of [RhCl(PPh3)3] with mixed anhydrides Ph2PO2CCRCR′R″(R = R′= H, R″= Me or CHCHMe; R = H, R′= R″= Me; R = Me, R′= H, R″= Ph) give complexes [RhCl(PPh3)n(Ph2PO2CCRCR′R″)](n= 1, R = R′= H, R″= Me or CHCHMe; n= 2, R = H, R′= R″= Me; R = Me, R′= H, R″= Ph; R = R′= H, R″= CHCHMe). For n= 1, the mixed anhydride is bound to the metal via the phosphorus atom and the double bond, whilst for n= 2 binding is through phosphorus alone. Treatment of [RhCl(PPh3)n(Ph2PO2CCRCR′R″)] with TlPF6 or AgSbF6 leads in all cases to complexes [Rh(PPh3)2(Ph2PO2CCRCR′R″)]+ in which the mixed anhydride is bound through the phosphorus atom and the carbonyl oxygen atom. Spectroscopic diagnostics for the various different bonding modes are discussed, whilst their occurrence is rationalised largely on steric grounds. The X-ray crystal structure of [RhCl(PPh3)(Ph2PO2CCHCHMe)] is described along with its curious fluxional behaviour. Crystals of this complex are monoclinic (space group P21/n), with a= 19.954(4), b= 13.250(4), c= 11.425(1)A, β= 91.66(2)°, and Z= 4. The structure was obtained from 3 721 observed intensities measured on an automatic diffractometer and refined to an R value of 0.0358. The complex is distorted square planar about rhodium with the co-ordination sites being occupied by the two phosphorus atoms, the chloride, and the CC of the mixed anhydride. The two phosphorus atoms are mutually cis. The CC bond length is 1.393(9)A, and there is significant pyramidalisation at the carbon atoms of the double bond, suggesting a fairly strong interaction between the double bond and the rhodium atom.

A 2,3-naphthoquinodimethane complex of ruthenium

Abstract Treatment of 2,3-dimethylnaphthalene with BuLi·TMED (TMED = tetramethylethylenediamine) gives 2-lithiomethyl-3-methyl-naphthalene·TMED, which in tu