Olivier Blacque

Synthesis and X-ray Crystal Structures of (C5HiPr4)Ln(BH4)2(THF)(Ln = Nd and Sm), Versatile Precursors for Polymerization Catalysts

The new half metallocenes [(C5HiPr4)Ln(BH4)2(THF)] [Ln = Sm (1) and Nd (2)], and [(C5HiPr4)U(BH4)3] (3) have been synthesized. The crystal structures of 1 and 2 and of the metallocenes [(C5HiPr4)2Ln(BH4)] [Ln = Sm (4) and Nd (5)] have been determined. The substitution of the BH4 groups of 1 and 2 by a nitrogen-based ligand is possible. In the presence of butyllithium, these complexes show an activity in isoprene and styrene polymerization.

New 1,1%- or 1,2- or 1,3-bis(diphenylphosphino)ferrocenes

The syntheses of ferrocenyl phosphines with bulky substituents are reported using the reaction between FeCl2 and the suitably substituted cyclopentadienyl salts, LiC5H3-1,3-(PPh2)2, LiC5H3-1-PPh2-3- t Bu, LiC5H2-1,2-(PPh2)2-4- t Bu. This strategy leads to bi-, tri- and tetraphosphines, which cannot be obtained by the other access paths used to prepare substituted ferrocenes. [C5H3-1,3(PPh2)2](C5H5)Fe, [C5H3-1-PPh2-3- t Bu]2Fe racemic and meso and [C5H2-1,2-(PPh2)2-4- t Bu](C5H5)Fe have been characterized by single-crystal X-ray diffraction studies.

Investigation into the reactivity of oxoniobocene complexes [Cp*2Nb(O)R] (Cp*=η5-C5Me5; R=H, OH, OMe) towards heterocumulenes: formation of carbamato and thiocarbamato complexes and catalytic cyclization of PhNCO

Abstract The reaction of [Cp*2NbCl2] (Cp*=η5-C5Me5) with KOH or Ba(OH)2·8H2O in THF was investigated under slightly modified conditions. In addition to the known complex [Cp*2Nb(O)H] (1), the new compound [Cp*2Nb(O)OH] (2) was formed. The reaction of 2 with PhNCS gave yellow [Cp*2Nb(O){SC(O)NHPh}] (3), while PhNCO formed yellow [Cp*2Nb(O){OC(O)NHPh}] (4). Complexes 3 and 4 were analytically and spectroscopically characterized. X-ray diffraction analyses of both compounds show that they contain either η1-S-thiocarbamato (3) or η1-O-carbamato ligand (4) along with a terminal NbO group. The reaction of 1 with one equivalent of PhNCO mainly gave orange [Cp*2NbH{OC(O)NPh}] (5) along with some 4. The molecular structure of 5 contains a niobocene unit comprising η2-N,O-carbamato chelate, which formally is a [2+2] cycloaddition product of the NbO group and the heterocumulene. A hydride ligand completes the coordination sphere around Nb. Reaction of 1 with excess PhNCO gave a mixture of heterocycles (PhNCO)2 (6) and (PhNCO)3 (7) in the approximate ratio 3:2. By contrast, the reaction of [Cp*2Nb(O)OMe] with PhNCO in molar ratios from 1:3 to 1:100 gave nearly pure triphenylisocyanurate 7.

Desulfurization and ring opening of thiirane induced by tantalocene trihydride complexes: synthesis, reactivity and X-ray structure of Cp′2Ta(S)(S-iPr) with Cp′=η5-C5H4tBu

The reaction of the tantalocene trihydride complexes Cp′ 2 TaH 3 1 (Cp′= η 5 -C 5 H 4 t Bu) or Cp″CpTaH 3 1′ (Cp″= η 5 -C 5 H 2 -1,2-Me 2 -4- t Bu) with propylene sulfide was found to proceed via an unprecedented sulfur transfer and regioselective ring opening reaction at once to yield sulfido-thiolato tantalocene complexes Cp′ 2 Ta(S)(S- i Pr) 2a whose structure has been determined by X-ray crystallography or Cp″CpTa(S)(S- i Pr) 2′a . Complex 1 reacts with ethylene sulfide to give Cp′ 2 Ta(S)(S–Et) 2b . The reactivity of 2a towards a variety of electrophilic moities has been investigated: protonation (with HBF 4 ) and alkylation (with MeI) reactions occur at the terminal sulfur ligand, leading to [Cp′ 2 Ta(SH)(S- i Pr)]BF 4 4a , [Cp′ 2 Ta(SMe)(S- i Pr)]I 5a ; the reaction of 2b with EtI was found to yield [Cp′ 2 Ta(S–Et) 2 ]I 6b . Complex 2a (or 2 ′) binds the unsaturated organometallic fragments [W(CO) 5 ] and [W(CO) 4 ]; the new heterobimetallic complexes Cp′ 2 Ta(S- i Pr)( μ -S)W(CO) 5 7a (or 7 ′ a ) and Cp′( μ -S,S- i Pr)]W(CO) 4 8a (or 8′a ) were formed. Inversion of configuration at the bridging μ -S atoms has been observed at low temperature for 8a and has been studied by dynamic 1 H-NMR spectroscopy.

REACTION OF DIPHENYLDIAZOMETHANE WITH N-METHYLOXY- AND N-ETHYLOXYCARBONYL-N-(2,2,2-TRICHLOROETHYLIDENE)AMINES

Reaction of the title imines with diphenyldiazomethane gives a Δ3-1,3,4-triazoline, which leads, after loss of dinitrogen, to a transient azomethine ylide. Subsequent elimination of ethyl or methyl chloroformate gives the unexpected 1,1-diphenyl-4,4-dichloro-2-aza-1,3-butadiene.

Tantalocenehydridephosphorus chemistry.: Some new complexes and crystal structures of [CpCp′TaH2(PMe2H)]PF6 (Cp=C5H5, Cp′=C5H2tBu(Me)2) and Cp2Ta(H)(μ-PPh2,H)Fe(CO)3

Abstract The aim of this paper is to look for a better knowledge of the behaviour of bent tantalocenes that bear hydrides, phosphorus PR2X (R=Me, Ph; X=H, lone pair) and cyclopentadienyl (Cp=C5H5, Cp′=C5H2tBu(Me)2, Cp*=C5Me5) ligands. An orbital control of regioselectivity of insertion of the PR2 phosphide fragment of chlorophosphines PR2Cl into the central TaH bond of trihydrides Cp2TaH3 leading to the formation of metallophosphonium cations is discussed. Neutralisation of cationic complexes with strong bases leads either to the Ta(V)–phosphide or to the Ta(III)–phosphine species depending on the nature of the cyclopentadienyl ligand; good electron donor Cp′ and Cp* rings favour the formation of Ta(V)–phosphide species, while C5H5 orients neutralisation towards Ta(III)–phosphine ones. These trends are roughly confirmed by DFT calculations. The X-ray structure of the first tantalocene phosphonium ionic compound [CpCp′TaH2(PMe2H)]PF6 (Cp′=C5H2tBu(Me)2) as well as that of the bimetallic complex Cp2Ta(H)(μ-PPh2,H)Fe(CO)3 are also reported.

Synthesis and Complexation of the Metalloligand {(η5‐C5H5)[η5‐C5Me3‐1,2‐(PPh2)2]TiCl2} (TiPHOS): The First Example of a 1,2‐Bis(diphenylphosphanyl)titanocene Derivative

The reaction of lithium 1,2-bis(diphenylphosphanyl)trimethylcyclopentadienide (1) with CpTiCl3 leads to the formation of the titanocene diphosphane {(η5-C5H5)[η5-C5Me3-1,2-(PPh2)2]TiCl2} (TiPHOS, 2). This metalloligand reacts readily with (NBD)Cr(CO)4 and W(CO)5(THF) to give, in both cases, the bimetallic chelate complexes (TiPHOS)Cr(CO)4 (3) and (TiPHOS)W(CO)4 (4). The structure of 4 has been determined by X-ray diffraction. The synthesis of a new early-late heterobimetallic complex (TiPHOS)Rh(CO)Cl (5) is reported.

Nucleophilic Additions of Sodium Alkoxides to 4,4‐Dichloro‐1,1‐diphenyl‐2‐azabuta‐1,3‐diene

The reaction of some sodium alkoxides with 4,4-dichloro-1,1-diphenyl-2-azabuta-1,3-diene is described. Whereas sodium methoxide, ethoxide or isopropoxide leads to 1,3-bis(alkoxy)- and/or 1,3,4-tris(alkoxy)-2-azabut-2-enes, the sodium salt of ethyl glycolate gives a Δ2-oxazoline. Mechanisms for the formation of these products are proposed.

Syntheses and properties of tetrathio- and tetraseleno metalates [(C5Me4R)2NbE2]2M (E=S, Se; M=Cr, Mo; R=Me, Et) with peripheric niobocene ligands

Abstract Reactions of Cp*2Nb(η2-S2)H 1 (Cp*=C5Me5 (a), C5Me4Et (b)) and Cp*2Nb(η2-Se2H) 3 with 0.5 equivalents of M(CO)6 (M=Cr, Mo) in boiling toluene give the CO free complexes [Cp*2NbE2]2M 4–7. X-ray diffraction analyses have been carried out for the Mo complexes 5a (E=S) and 7a (E=Se) showing that the structures contain ME4 tetrahedral cores with two attached niobocene ligands thus forming a nearly linear trimetallic unit. Absorption spectra and electrochemical studies of complexes 4–7 are described. Characteristic of the novel CrSe4 chromophor are four reversible one electron redox steps. Chemical oxidation of 4a and 5a with [(C5H5)2Fe]PF6 gives the salts {[Cp*2NbS2]2M}PF6 (M=Cr, Mo) 10 and 11. A qualitative EHMO analysis provides evidence for a strong delocalisation of electron density over the whole metal–ligand system.

New insights into the reactivity of the tantalocene hydride Cp′2TaH3 (Cp′=η5-tBuC5H4). Synthesis and characterisation of cationic Ta(V) complexes with 0,0 and S,N chelating ligands

Abstract Reaction of various neutral LXH bidentate ligands (2-aminobenzoic acid, acetylacetone, dibenzoylmethan and 2-aminobenzenethiol) with [Cp′2TaH2]+, obtained in situ from Cp′2TaH3 treated with triphenylmethan cation, affords after dihydrogen elimination the corresponding cationic species [Cp′2Ta(H)(LX)]+ in BF4 or PF6 salts. Complexes [Cp′2TaH(η2-O2CC6H4-o-NH2O,O′)]PF6 (3), {Cp′2Ta[η2-OC(Me)CHC(Me)OO,O′]}BF4 (4a), {Cp′2TaH[η2-OC(Ph)CHC(Ph)OO,O′]}BF4 (4b) and [Cp′2TaH(η2-SC6H4-o-NH2S,N)]PF6 (5) are characterised by analytical and spectroscopic methods. With thiopyridine, the kinetic (6) and the thermodynamic (6′) isomers [Cp′2TaH(η2-2-SC5H4NS,N)]PF6 are identified. Crystal structures are reported for complexes 3, 5 and 6′.