Roberto Rossi

Synthesis and Characterisation of tetrahedro-Tetraphosphorus Complexes of Rhenium – Evidence for the First Bridging Complex of White Phosphorus

Reaction of white phosphorus with [(triphos)Re(CO)2(OTf)] (1) in dichloromethane affords the new tetraphosphorus complex [(triphos)Re(CO)2(η1-P4)](OTf) (2) [triphos = MeC(CH2PPh2)3; OTf = OSO2CF3]. Compound 2 reacts with a second equivalent of 1 to give the binuclear complex [{(triphos)Re(CO)2}2(μ,η1,η1-P4)](OTf)2 (3) in which a tetrahedro-P4 ligand behaves as tethering unit between two [(triphos)Re(CO)2]+ moieties. Complexes 2 and 3 represent the first soluble metal complexes of the tetraphosphorus molecule where the P4 ligand has not undergone any major modification.

Reactivity of oxotetrachlororhenate(V) with bidentate and tetradentate schiff bases containing oxygen and nitrogen donors

Abstract The five-coordinated rhenium(V) [(C 6 H 5 ) 4 As][ReOCl 4 ] compound reacts with bidentate and tetradentate Schiff bases containing oxygen and nitrogen donors to give six-coordinated complexes. With the ligands (LH) (L = N-methylsalicylidene-iminate, N-phenylsalicylideneiminate, half N, N′-ethylenebis(salicylideneiminate) and 8-hydroxyquinolinate), the complexes [(C 6 H 5 ) 4 As][ReOCl 4 (LH)], [(C 6 H 5 ) 4 As][ReOCl 3 (L)] or ReOCl(L) 2 are obtained. The complexes were characterized by elemental analysis and conductivity measurements. Their stereochemistries were postulated on the basis of infrared spectra and X-ray data previously reported for analogous oxo-rhenium(V) compounds.

Reactivity of the ReOX3(PPh3)2 complexes (X = Cl or Br) with Schiff bases

SummaryThe reactions of ReOX3(PPh3)2 (X = CI or Br) withN-methylsalicylideneimine (Me-saIH),N-phenylsalicylideneimine (Ph-saIH),N,N′-ethylenebis(salicyli(leneimine) [(SaIH)2en] and 8-hvdroxyquinoline (Oxinell) are here reported. They give rise to the ReOX2(Me-sal)PPh2. ReOX-(Me-sal)2, ReOX2(Ph-sal)PPh3, ReOX(Ph-sal),, Re2O2X4-(Sal2en)(PPh3)2, ReOX2(Oxine)PPh, and ReOX(Oxine)2 complexes.

Structure oftrans-dichlorooxobis(triphenylphosphine)rhenium(V), ReCl2O(OEt)(Ph3P)2

C38H35Cl2O2P2Re,Mr=842, triclinic,P¯1,a=17.71(2),b=11.33(1),c=9.82(1) Å,α=114.60(3),β=90.84(3), γ=78.05(3),V=1747(2) Å3,Dm(flotation)=1.60,Dx=1.60 Mg m−3 forZ=2, MoKα, λ=0.7107 Å,μ=41.6 cm−1,F(000)=836, room temperature. The structure was solved by standard methods from diffractometer data and refined to a conventionalR of 3.4% for 5412 observed reflections. The Re atom is six coordinate octahedral withtrans-Cl atoms andtrans-Ph3P groups. Relevant bond distances are: Re-P 2.533(1) and 2.535(1) Å, Re-O(ethoxo) 1.888(4) Å, and Re-O(oxide) 1.699(4) Å. The ethyl chain is partially disordered.

Synthesis and characterization of new formamidino and triazenidocomplexes of rhenium(I): [Re(CO)2(PPh3)2(ArNxxxXxxxNAr)] (X = CH,N)

Abstract [Re(CO) 3 (PPh 3 ) 2 Cl] reacts with Li(ArNxxxXxxxNAr) (X = CH, N; Ar = p -CH 3 C 6 H 4 , C 6 H 5 , p -ClC 6 H 4 , p -FC 6 H 4 in boiling THF to yiled[[Re(CO) 2 (PPh 3 ) 2 - (ArNxxxXxxxNAr)]. The structure of these new complexes and the mode of coordination of the organonitrogen ligand are discussed on the basis of i.r. and 1 H n.m.r spectra

A new uranium(IV) organometallic tetrahydroborate complex. The preparation and characterization of the bis(cyclopentadienyl)uranium (iv) bis(tetrahydroborate):(η5c5h5)2u(bh4)2 ☆

The synthesis and characterization of (η 5 -C 5 H 5 ) 2 U(BH 4 ) 2 are reported. I.r. and room temperature Hnmr data support a tridentate ligation and themagnetic equivalence of the bridge and terminal BH − 4 hydrogen atoms. Preliminary X-ray analysis results suggest a structure consisting of the uranium atom in an approximately tetrahedral configuration surrounded by two pentahaptocyc o pentadienyl rings and two tetrahydroborate groups.

New rhenium complexes with phosphinite PPh2OR or phosphonite PPh(OR)2(R = Me, Et or Pri) ligands: synthesis and protonation of various polyhydrides

The rhenium complexes [ReOCl3L2] and [ReCl3L3][L = PPh2OMe, PPh2OEt, PPh2OPri, PPh(OEt)2 or PPh(OPri)2] were prepared by allowing [ReOCl3(AsPh3)2] to react with the appropriate amount of phosphinite or phosphonite. Treatment of [ReCl3L3] with CO and p-MeC6H4NC afforded the mer-trans-[ReCl(CO)3L2] and [ReCl2(p-MeC6H4NC)4L]BPh4 complexes, respectively. Treatment of [ReOCl3L2] with NaBH4 gave [Re2H8L4], but in the presence of phosphinite or phosphonite the trihydrides [ReH3L4] were obtained. Treatment of [ReCl3L3] with NaBH4 gave instead pentahydride complexes [ReH5L3]. All the multihydrides were characterised as ‘classical’ species by variable-temperature NMR spectroscopy (1H and 31P) and T1 measurements. Protonation of [Re2H8L4] and [ReH3L4] with HBF4·Et2O gave the classical hydride cations [Re2H9L4]+ and [ReH4L4]+, respectively, while similar treatment of [ReH5L3] gave a species formulated as containing an η2-H2 ligand, [ReH4(η2-H2)L3]+ on the basis of T1(min) evidence.

Synthesis, properties and X-ray crystal structure of schiff base organoimido complexes of rhenium(V)

Abstract Re(NR)Cl 3 (PPh 3 )( 2 (R = p-CH 3 C 6 H 4 , CH 3 ) react with polydentate ligands (LH = N-methyl-, N-phenyl-, N-tolyl-salicylideneimine, half, N,N′-ethylenebis-, half N,N′-propylenebis-(salicylideneimine), 8-hydroxyquinoline and LH 2 = N-2-hydroxyphenylsalicylideneimine) to yield complexes of the type Re(NR)Cl 2- (L)PPh 3 . With 8-hydroxyquinoline the bisubstituted Re(NR)Cl(L) 2 complexes are also obtained. The compounds were characterized by elemental analysis, molecular weight, and i.r. spectra. The crystal and molecular structures of two arylimido complexes, Re(p-CH 3 C 6 H 4 N)Cl 2 )RNue5fbCHC 6 H 4 O)PPh 3 with R = C 6 H 5 or CH 3 , were determined from X-ray crystallography based on diffractometer data. The phenyl compound crystallizes in space group P2 1 /c of the monoclinic system, with a = 15.340(5) A, b = 21.115(6) A, c = 10.605(5) A, β = 91.36(5)°, and D x = 1.59 g cm −3 for four formula units in the cell. The structure has been refined by least-squares to the final R factor of 4.7% for the 3931 reflexions above background. The methyl compound crystallizes in space group P 1 of the triclinic system, with a = 13.457(5) A, b = 11.795(5) A, c = 10.997(5) A, α = 112.16(5)°, β = 108.17(5)°, γ = 86.36(5)°, and D x = 1.64 g cm −3 for two formula units in the cell. The structure has been refined by least-squares to the final R factor of 8.0% for the 4891 reflexions above background. The overall molecular structure is the same for both complexes. The Re atom is in a distorted octahedral configuration with two Cl atoms trans to one another, the arylimido group (bonded to Re via the N atom) trans to the O atom of the bidentate ligand, and the PPh 3 group trans to the N atom of the bidentate ligand. Bond distances and angles in the two molecules agree well. Mean values for some bond distances involving rhenium are: Reue5f8Cl 2.418 A; Reue5f8P 2.44 A; Reue5f8O 1.98 A; Reue5f8N(arylimido) 1.73 A; Reue5f8N 2.14 A.

Synthesis, Characterization, and Interconversion of the Rhenium Polyhydrides [ReH3(η4-NP3)] and [ReH4(η4-NP3)]+ {NP3 = tris[2-(diphenylphosphanyl)ethyl]amine}

The rhenium(III) dichloride complex [ReCl2(η4-NP3)]Cl (1) was prepared from [ReCl3(CH3CN)(PPh3)2] by treatment with the tripodal tetradentate ligand N(CH2CH2PPh2)3 (NP3) in ethanol. The reaction of 1 with LiAlH4 in THF gave the rhenium(III) trihydride [ReH3(η4-NP3)] (2), which was converted into the rhenium(V) tetrahydride [ReH4(η4-NP3)]BPh4 (3) by protonation in CH2Cl2 with HBF4·OMe2, followed by a metathetical reaction with NaBPh4. The classical polyhydride nature of 2 and 3, as well as the overall molecular structures in solution, were determined by NMR spectroscopy, 1H NMR relaxation, and IR spectroscopy. The polyhydride complexes 2 and 3 are stereochemically nonrigid in solution, and the thermodynamic parameters associated with the fluxional processes were determined by variable-temperature NMR studies. A single-crystal X-ray analysis of 3 has shown the complex cation [ReH4(η4-NP3)]+ to be eight-coordinated by the four donor atoms of NP3 and by four terminal hydride ligands in a distorted dodecahedral geometry. An in situ IR study in CH2Cl2 has shown that the protonation of 3 occurs regioselectively at the metal center with no formation of a dihydrogen complex. Kinetic hydrogen bond products of the formula [(η4-NP3)H3Re···HOR] (ROH = C2H5OH, CFH2CH2OH, CF3CH2OH) were intercepted by IR spectroscopy at low temperature. The thermodynamic parameters associated with the formation of the hydrogen bond adducts were determined by either IR spectroscopy applying the Iogansen equation or van’t Hoff plots of the formation constant vs. temperature.

Rhenium(III) and rhenium(V) complexes stabilized by the potentially tetradentate ligand tris(2-diphenylphosphinoethyl)amine

The reaction of the rhenium(V) nitrido complex [Re(N)Cl2(PPh3)2] with the tripodal ligand N(CH2CH2PPh2)3 (NP3 )i n THF gave [Re(N)Cl2( 2 -P,P-NP3)] (1) in which NP3 acts as a tridentate ligand using the nitrogen and two phosphorus donors for coordination. Refluxing 1 in a polar solvent such as ethanol produced [( 4 -NP3)Re(N)Cl]Cl (2) in which NP3 acts as a tetradentate ligand. Treatment of complex [Re(O)Cl3(AsPh3)2] containing the [ReO] 3 + core with NP3 in THF yielded [ReCl3{ 3 -N,P,P(N{CH2CH2Ph2}2{CH2CH2P(O)Ph2})}] (3). Complexes 1 and 3 have been characterized by single-crystal X-ray analyses.