Rhodium cationic complexes using dithioethers as chiral ligands. Application in styrene hydroformylation

Addition of the dithioethers (−)-DIOSR2 (R=Me, iPr) (2,3-O-isopropylidene-1,4-dimethyl (and diisopropyl) thioether-L-threitol) to a dichloromethane solution of [Rh(COD)2]ClO4 (COD=1,5-cyclooctadiene) yielded the mononuclear complexes [Rh(COD)(DIOSR2)]ClO4. X-ray diffraction methods showed that the [Rh(COD)(DIOSiPr2)]ClO4 complex had an square-planar coordination geometry at the rhodium atom with the iPr groups in anti position. Cyclooctadiene complexes react with carbon monoxide to form dinuclear tetracarbonylated complexes [(CO)2Rh(μ-DIOSR2)2(CO)2](ClO4)2. [Rh(COD)(DIOSR2)]ClO4 are active catalyst precursors in styrene hydroformylation at 30 atm and 65°C which give conversions of up to 99% with a regioselectivity in 2-phenylpropanal as high as 74%. In all cases enantioselectivities are low.

9,10-Dimetallatriptycenes of group 14: a structural study

From ortho-phenylenemagnesium (1), 9-phenyl-9-germa-10-silatriptycene (5) was prepared via a simple one pot procedure. The previously prepared 9-methyl-10-phenyl-9,10-digermatriptycene (4) and 5 are the first germanium-containing 9,10-dimetallatriptycenes to be structurally characterised. The availability of these structural data allows a comparative discussion of 9,10-dimetallatriptycenes of Group 14.

Metal complexes with atropisomeric sulfur ligands in asymmetric hydroformylation X-ray structure of [Rh2(μ-biphes)(cod)2] (H2biphes = 4,4′-biphenanthrene-3,3′-dithiol)

The addition of the atropisomeric racemic sulfur compound 4,4′-biphenanthrene-3,3′-dithiol (H2 biphes) to a dichloromethane solution of [{M(μ-OMe)(cod)}2] (M = Rh, Ir, cod = cycloocta-1,5-diene) afforded the dithiolate-bridged complexes [{Rh2(μ-biphes)(cod)2}n] (n = 2 5 or n = 1 6) and [{Ir2(μ-biphes)(cod)2}n]·nCH2Cl27. When 1,1′-binaphthalene-2,2′-dithiol (H2 binas) reacted with [{Ir(μ-OMe)(cod)}2], complex [Ir2(μ-binas)(cod)2] 8 was obtained. Complexes 5 and 6 reacted with carbon monoxide to give the dinuclear tetracarbonyl complex [Rh2(μ-biphes)(CO)4] 9. The reaction of 9 with PR3 provided the mixed-ligand complexes [{Rh2(μ-biphes)(CO)2(PR3)2}2] · xCH2Cl2 (R = Ph, x = 2 10, C6H11, x = 1 11) and [{Rh2(μ-biphes)(CO)3(PR3)}2] · CH2Cl212 (R = OC6H4But-o). The crystal structure of 6 was determined by X-ray diffraction. Reaction of the dithioether ligand Me2biphes with [Rh(cod)2]ClO4 in CH2Cl2 solution afforded the cationic complex [Rh(cod)(Me2biphes)]ClO4 · CH2Cl213. Asymmetric hydroformylation of styrene was performed using the complexes described. The extent of aldehyde conversion ranges from 53 to 100%, with selectivities towards branched aldehydes in the range 51 to 96%. The enantioselectivities were quite low and did not exceed 20%.

Mononuclear Pt(II) and Pd(II) 1,4-dithiolato complexes. Crystal structures of [Pt((−) DIOS) (PPh3)2] and [Pd(S(CH2) 4S)(Ph2P(CH2) 3PPh2)]. Application in styrene hydroformylation

Addition of 1,4-dithiols to dichloromethane solutions of [PtCl2(P-P)] (P-P = (PPh3)2, Ph2P(CH2)3PPh2, Phd2P(CH2)4PPh2; 1,4-dithiols = HS(CH2)4SH, (−)DIOSH2 (2,3-O-isopropylidene-1,4-dithiol-l-threitol), BINASH2 (1,1′-dinaphthalene-2,2′-dithiol)) in the presence of NEt3 yielded the mononuclear complexes [Pt(1,4-dithiolato)(P-P)]. Related palladium(II) complexes [Pd(dithiolato)(P-P)] (P-P=Ph2P(CH2)3PPh2, Ph2P(CH2)4PPh2; dithiolato = −S(CH2)4S−, (−)-DIOS) were prepared by the same method. The structure of [Pt((−)DIOS)(PPh3)2] and [Pd(S(CH2)4S)(Ph2P(CH2)3PPh2)] complexes was determined by X-ray diffraction methods. Pt—dithiolato—SnC12 systems are active in the hydroformylation of styrene. At 100 atm and 125°C [Pt(dithiolate)(P-P)]/SnCl2 (Pt:Sn = 20) systems provided aldehyde conversion up to 80%.

Fulvalene titanium and zirconium complexes: synthesis and NMR study of phosphanido-, alkyl-, and alkynyl-derivatives. X-ray crystal structures of [{Ti(η5−C5H5)(μ−PPH2)}2{μ−(η5−C5H4−η5−C5H4)}] and [{Zr(η5−C5H5)(μ−C≡CSiMe3)}2{μ−(η5−C5H4−η5−C5H4)}]

Reaction of with one or two equivalents of LiPPh2 afforded the new phosphanidometal(III) complexes . Reaction of 2 with LiC≡CSiMe3 led to the diamagnetic zirconium(III) alkynyl derivative [{Zr(C5H5)(μ−C≡CSiMe3)}2(μ−η5−C5H4−η5−C5H4], 7. Alkylation of 6 with LiCH2CMe2Ph gave [{Zr(η5−C5H5)(CH2CMe2Ph)2}2{μ−(η5−C5H4)}], 8. A detailed NMR study of complexes 3 and 4 allowed the observation of the spectral behaviour of the eight different fulvalene protons through their coupling to the 31P nucleus. The fluxional behaviour of complex 7 was studied by dynamic DNMR, and kinetic parameters for the σ-π-conversion of the alkynyl ligand were determined. The molecular structures of complexes 3 and 7 were determined by X-ray diffraction methods.

Synthesis and structure of Ir4Sn3(CO)6{CH(SiMe3)2}5O3; a heterometallic ‘raft’ with sail hoisted!

Heterometallic raft clusters have been obtained previously for a variety of metals but none for tin and iridium, and more significantly none to date have had metal groups bonded above the raft plane. We report a hexametallic Ir4Sn2 raft to which a third tin group is attached by a single short IrSn bond and three IrOSn bridges.

Fulvalene cyclopentadienyl titanium and zirconium(III) and -(IV) complexes. X-Ray crystal structure of [{Ti(η5-C5H5) Cl}2 (μ-O)(μ-η5-η5-C10H8)]

The reaction of the fulvalene titanium(III) hydride [{Ti(η5-C5H5)(μ-H)}2(μ-η5-η5-C10H8)] (1) with chlorine leads to [{Ti(η5-C5H5)(μ-Cl)}2(μ-η5-η5-C10H8)] (3) and [{Ti(η5-C5H5)Cl2}2(μ-η5-η5-C10H8)] (4). The reaction of 3 with azobenzene, in wet toluene, gives [{Ti(η5-C5H5)Cl}2(μ-O)(μ-η5-η5-C10H8)] (5) and 1,2-diphenyl hydrazine. The alkylation of 4 and the analogous zirconium complex [{Zr(η5-C5H55)Cl2}2(μ-η5-η5-C10H8)] (2) with LiCH2SiMe3 or LiCH3 permits isolation of the tetraalkyl derivatives [{M(η5-C5H5)(CH2SiMe3)2}2(μ-η5-η5-C10H8)] (M  Ti (6); Zr (8)) and [{Ti(η5-C5H5)(CH3)2}2(μ-η5-η5C10H8)] (7). All the new fulvalene compounds were characterized by IR, and 1H and 13C NMR spectroscope, and mass spectra and 5 by X-ray diffraction. The structure of 5 is very similar to that of the comparable TiIV compound [{Ti(η5-C5H5)2Cl}2(μ-O)] except for the smaller TiOTi angle (159.4° against 173.81°) and a significant deviation from linearity.

A simplified, high-yield synthesis, and crystal structure of [tris{bis(2,4,6-triisopropylphenyl)tin}]

The species [{Sn(C2H2iPr3-2,4,6)2}3] has been obtained in a simple, essentially quantitative, synthesis from SnCl2 and ArLi in diethyl ether at low temperature. The crystal structure analysis confirms the trimeric nature of the molecular units but reveals some unusual features. The crystal contains the unusual feature of an asymmetric unit that consists of three units of [{SnAr2}3] in P21/c; the molecular unit is a scalene triangle, showing high consistency between the three molecules, in contrast to analogous trimeric species of silicon or germanium. The SnSn bonds are lengthened (average value 2.942 Å) owing to steric crowding.

Synthesis, structure and reactivity of the novel tetratin species bromoheptakis(2,6-diethylphenyl)-cyclotetrastannabutane

Metallation of ArBr (Ar = 2,6-diethylphenyl) with Li powder in diethyl ether, followed by addition of stannous chloride at low temperature does not give the expected oligomeric diarylstannane but an essentially quantitative yield of the novel tetrastannabutane [{SnAr2}3SnArBr]. Some reactions of the new species are reported.

Synthesis of the first-membered ring compound containing three tin atoms and one oxygen. The crystal structure of the species [O{Sn(C6H3Et2-2,6)2}3]

Aerial oxidation of the novel homocyclic tetratin species [{SnAr2}3SnArBr] (1) [1] (Ar  C6H3Et2-2,6) affords the tritin heterocycle [O{Sn(C6H3Et2-2,6)2}3] (2), which has been crystallographically characterised; 2 is the first reported oxatristannacyclobutane, and the first heterocyclic tin species having both tintin and tinheteroatom bonds.

The synthesis and properties of [Fe3(CO)11(RCN)] derivatives, and a high-yield general route to mono- and di-substituted derivatives of [Fe3(CO)12]; the crystal and molecular structure of [Fe3(CO)11(NCC6H4-2-Me)]

The clusters [Fe3(CO)11(RCN)] (1: R = Me, C3H5, C6H5, or C6H4-2-Me) have been prepared at low temperature from [Fe3(CO)12] and RCN in the presence of Me3NO. Compounds 1 react essentially quantitatively with a wide range of two-electron donors, L, (viz.: CO, PPh3, P(OMe)3, PPh2H, PPh2Me, PF3, CyNC (Cy = cyclohexyl), P(OEt)3, SbPh3, PBu3, AsPh3, or SnR2 (R = CH(SiMe3)2)) to give [Fe3(CO)11L] (2). In some cases (2), on treatment with Me3NO and then L′ (L′ = a second two-electron donor) yields [Fe3(CO)10LL′] in high yield. The crystal and molecular structures of 1 (L = NCC6H4Me-2) have been determined by a full single crystal structure analysis, and shown to have an axial nitrile coordinated at the unique iron atom, with two CO groups bridging the other two metal atoms.

Metal cluster expansion by addition of low valent group 14 reagents: III. Reaction of bis[bis(trimethylsilyl)methyl]tin with M3(CO)12 or its derivatives (M = Fe, Ru, or Os): the crystal and molecular structures of M3(μ-SnR2)2(CO)10(R = CH(SiMe3)2; M = Ru or Os)

The stannylene [SnR2] (R = CH(SiMe3)2) reacts in different ways with the three dodecacarbonyls of the iron triad: [Fe3(CO)12] gives [Fe2(CO)8(μ-SnR2)], [Ru3(CO)12] gives the planar pentametallic cluster [Ru3(CO)10(μ-SnR2)2], for which a full structural analysis is reported, while [Os3(CO)12] fails to react. Different products are also obtained from three nitrile derivatives: [Fe3-(CO)11(MeCN)] gives [Fe2(CO)6(μ-SnR2)2], which has a structure significantly different from that of known Fe2Sn2 clusters, [Ru3(CO)10(MeCN)2] gives the pentametallic cluster described above, while [Os3(CO)10(MeCN)2] gives the isostructural osmium analogue, which shows the unusual feature of a CO group bridging two osmium atoms.

A hydrogen-1 nuclear magnetic resonance, mass spectral and extended Hückel study of some olefin complexes of rhodium(I) and iridium(I) and the crystal and molecular structure of η4-2,4-dimethylpenta-1,4-diene(η5-formylcyclopentadienyl)rhodium(I)

A 1H NMR study of monosubstituted η-cyclopentadienyl-rhodium(I) complexes of type LLRh(C5H4X) and -iridium(I) complexes of type L2Ir(C5H4X) (L = ethene, LL = 1,3- or 1,5-diolefin; X = C(C6H5)3, CHO, or COOCH3) has been carried out. For complexes of both metals in which the neutral ligand is ethene or a non-conjugated diolefin the NMR spectra of the cyclopentadienyl protons are unusual in that H(2), H(5) resonate to high field either at room temperature or below. The corresponding NMR spectra for the cyclopentadienyl ring protons of complexes where the neutral ligand is a conjugated diene are, with one exception, normal. A single crystal X-ray structural analysis of (η4-2,4-dimethylpenta-1,4-diene)(η5-formylcyclopentadienyl)rhodium(I) (which exhibits an abnormal 1H NMR spectrum) reveals substantial localisation of electron density in the C(3)C(4) Cp ring bond (1.283(33) Å) which may be consistent with a contribution from an ‘allyl-ene’ rotamer to the ring—metal bonding scheme. An extended Hückel calculation with self consistent charge iteration was performed on this complex. The results predict a greater Mulliken overlap population for the C(3)C(4) bond in the cyclopentadienyl ring and show that the localisation is dependent on both the Cp ring substituent and the nature of the diolefin. The mass spectral fragmentation patterns of some representative diene complexes of iridium(I) and rhodium(I) are presented.

Homoleptic alkenyls of the early transition metals and related compounds

The first stable homoleptic alkenyls of the early transition metals, MRn, (R = C(Ph)=CMe2; M = Ti, Zr, Hf, n = 4; and M = Cr, n = 3) and the related species (C5H5)2MR2 (M = Ti, Zr) and (C5H5)2Zr(Cl)R have been prepared using appropriate organolithium reagents. Cleavage and insertion reactions are reported for the new compounds.

The synthesis, structure, and reactions of some simple unsaturated σ-hydrocarbylplatinum(II) complexes

Trimethyltin compounds Me3SnR(R = CHCH2, CFCF2, or CCPh) are selective reagents for the synthesis of unsaturated hydrocarbyl derivatives such as trans-PtCl(R)(PPhEt2)2, by R/Cl exchange or oxidative addition (e.g., to Pt(PPh3)3); single crystal X-ray analyses of two such compounds (R = CHCH2 or CCPh) show that the trans-influence of R has only a low sensitivity to hybridisation at carbon, with sp3 > sp ⩾ sp2.