Michèle Dartiguenave

Crystal and molecular structures of transition metal complexes with N- and C-bonded diazoalkane ligands

Abstract The review covers structural and physicochemical studies on diazoalkanes N-coordinated to transition metals and encompasses all collected crystal structures. Our goal is to provide a classification of the complexes based on the metal, ranging from early to late transition metals, the nuclearity of the complex (mono, dinuclear, clusters), the electronic configuration of the metal (d 0 to d 10 ) and the bonding mode of the diazoalkanes. Interestingly, the variety of structures may be rationalized within the valence bond formalism, the reactions being essentially oxidative addition of diazoalkane on the metal complexes giving hydrazonido (-2- ligand). C-coordinated diazoalkyl complexes are still restricted to a few metals and a few diazosubstituents and their chemistry is not well developed.

Bidentate phosphinophenol R2POH ligands. Oxo and imido Re(V) complexes of 2-diphenylphosphinomethyl-4-methylphenol (POH). Crystal structure of ReOCl(PO)2

Abstract The PPh 3 ligands were displaced and ReOCl 3 (Pue5f8OH) 2 ( 1 ) was formed when ReOCl 3 (PPh 3 ) 2 and 2 equiv. of the title ligand (Pue5f8OH) were refluxed in acetonitrile. In the presence of the proton quencher NEt 3 , ligand deprotonation took place and the bis-chelate complex ReOCl(Pue5f8O) 2 ( 2 ) was isolated. Under similar conditions, ReO(OEt)(Pue5f8O) 2 ( 3 ) was obtained from ReO(OEt)Cl 2 (PPh 3 ) 2 . NMR data are consistent with the trans -O–Reue605O- cis -P,P ‘twisted’ octahedral geometry for these species. The corresponding phenylimido complex Re(NPh)Cl(Pue5f8O) 2 ( 4 ), similarly prepared from Re(NPh)Cl 3 (PPh 3 ) 2 , adopts the trans -O–Re–NPh- trans -P,P arrangement. The structure of 2 was confirmed by X-ray diffraction. The methylene group in the side-arm imparts flexibility to the chelate ring and allows the bond angles to be closer to the ideal octahedral values than in the corresponding diphenylphosphinophenolato compound. The six-membered rings adopt a flattened boat conformation bringing the phenolate unit out of the coordination plane and making the overall van der Waals envelope substantially different from that of the diphenylphosphinophenol-based complex.

Bidentate phosphinophenol ligands. Preparation and electrochemistry of the Re(III) complexes of 2-(diphenylphosphinomethyl)-4-methylphenol (P1OH) and 2-diphenylphosphinophenol (P2OH). Crystal and molecular structure of mer-Re[P1O]3

Abstract The reaction of 2-(diphenylphosphinomethyl)-4-methylphenol (P1ue5f8OH) and 2-diphenylphosphinophenol (P2ue5f8OH) on ReCl3(MeCN)(PPh3)2 in a 3:1 ratio leads to the formation of the homoleptic Re(III) complexes Re(P1ue5f8O)3 (1) and Re(P2ue5f8O)3 (2) in high yield. 1 is reasonably stable in air in the solid state and in solution, which is not the case for 2. Orange–red crystals of 1 contain distorted octahedral Re entities in which the metal is coordinated to three bidentate phosphinophenolato ligands in the mer configuration. Cyclic voltammetry of 1 and 2 shows two well defined monoelectronic quasi-reversible redox waves, one reductive attributed to the Re(III)/Re(II) couple and one oxidative due to the Re(III)/Re(IV) one. A second oxidative wave, attributed to the Re(IV)/Re(V) couple, is reversible only for 1, indicating the lower stability of 2 toward oxidation. In agreement with this, 2 gives, in air, the Re(V)-oxo species ReO(Oue5f8P2ue605O)(P2ue5f8O)2 (3) quantitatively, whose structure is confirmed by X-ray diffraction.

Bidentate phosphinophenol ligand: synthesis and characterization of oxo and phenylimido rhenium(V) complexes of 2-diisopropylphosphinophenol

Abstract Six-coordinate, monosubstituted and disubstituted phosphinophenol complexes ReYX2(PPh3)(P∼O) and ReYX(P∼O)2 (Y=O, NPh; X=Cl, Br, I) were obtained by reacting 2-diisopropylphosphinophenol (P∼OH) with ReOX3(PPh3)2 and Re(NPh)X3(PPh3)2 in toluene. A mixture of the monosubstituted and disubstituted complexes ReYX2(PPh3)(P∼O) and ReYX(P∼O)2 was precipitated when the reactions were performed with a 2:1 ligand to metal ratio. Excess ligand (4 equiv.) was needed to obtain quantitatively the disubstituted complexes. 1H and 31P{1H} NMR show that all monosubstituted and disubstituted complexes exist as single isomers with a trans-P,P ‘twisted’ octahedral geometry, the site trans to the multiple bond being filled by the oxygen donor of one P∼O ligand. The compounds were also characterized by microanalysis, IR and mass spectrometry.

A simplified route to the synthesis of new 99mTc-specific tetradentate ligands

Abstract The synthesis of two new N 2 S 2 or N 2 SO tetradentate ligands and the preparation of their technetium-99m complexes are reported. Each ligand leads to a unique 99m Tc-complex with an excellent radiochemical yield. The in vivo stability of these complexes was determined by serum stability and cysteine challenge studies.

N-(2-pyridyl)-3-phenyl-2-propene amide (O-N) complexes fo copper(II), nickel(II), cobalt(II) and palladium(II). Crystal and molecular structure of Cu(O-N)2(CF3SO3)2

Abstract The reaction of the title ligand N-(2-pyridyl)-3-phenyl-2-propene amide (O-N) with MX2 salts yields compounds of the type M(O-N)2X2 and [M(O-N)2(H2O)2]X2, which were characterized by elemental analysis, magnetic moments and IR and EPR spectroscopies. From the IR spectra the ligand is found to be bidentate via the pyridyl nitrogen and the amide oxygen, except in [Pd(O-N)2Cl2] where only the pyridyl ring is coordinated. The magnetic moments, IR spectra and thermograms of the M(O-N)2(NO3)2·3H2O compounds [M = nickel(II), cobalt(II)] are consistent with the presence of trans-[M(O-N)2(H2O)2]2+ ions, similar to the trans-[Zn(O-N)2(CH3OH)2]2+ species observed earlier. The EPR spectra of the trans-Cu(O-N)2X2 compounds (X = NO3−, CF3SO3−) indicate an elongated octahedral coordination with equatorial bidentate (O-N) ligands and solvent molecules or anions in axial sites. The solid-state spectra reveal the presence of more than one type of copper(II) centre. The crystal structure of trans-Cu(O-N)2(CF3SO3)2 was determined by X-ray diffraction. The unit cell contains two types of discrete trans-Cu(O-N)2(CF3SO3)2 molecules, in which bidentate (O-N) ligands are strongly bonded to the equatorial sites of a tetragonally distorted octahedron. The axial positions are filled by

Chlorobis-[2-(diphenylphosphino)-phenolato-O,P]oxorhenium(V)

The title compound, [ReClO(C 18 H 14 OP) 2 ], contains severely distorted octahedra with a cis,cis,cis configuration. One of the phenolate O atoms is trans to the Re=O bond, whereas the two P atoms occupy cis sites. Departure from octahedral geometry can be interpreted in terms of the steric hindrance between the phosphine groups, the small bite of the P-O chelating agent and the tendency of the Re=O bond to repel the adjacent bonds. Bond lengths are Re=O 1.686(4), Re-Cl 2.394(2), Re-P 2.443 (2) and 2.451 (2), and Re-O(phenolate) 2.003 (4) (trans to Re=O) and 1.987 (4) A (trans to P).

Methylnickel compounds containing bridging and monodentate carboxylate ligands

Abstract Dinuclear methylnickel carboxylates [NiMe(OOCR)(PMe3)]2 (R=cyclohexyl (1); CH(C6H5)2 (2); C(C6H5)3 (3); 9-anthracenyl (4); bicyclo[3.2.2]nonane-1-yl (5); C6H5 (6); 2-NH2-C6H4 (7); 4-OH-C6H4 (8); 1-naphthyl (9); 2-naphthyl (10); CF3 (11); CH2Cl (12); CHCl2 (13); CH2Br (14)) were prepared by reacting [NiMe(OMe)(PMe3)]2 and the corresponding carboxylic acid. Spectroscopic data indicate μ-carboxylato ligands in eight-membered metallocycles (NiOCO)2, while mononuclear methylnickel carboxylates NiMe(OOCR)(PMe3)2 (1a, 2a, 4a–10a, 12a–14a) contain unidentate carboxylate anions. Upon reaction with trimethylphosphine 11 forms an ionic methylnickel complex [NiMeL4]+CF3COO− (15) rather than 11a. Compound 6 crystallizes in the monoclinic space group C2/c with a=12.327(3), b=12.885(4), c=16.495(6) A,β=102.93(2)°, V=2553(2) A3, Z=4. Final discrepancy indices are R = 0.0631 and Rw=0.0659. The molecule 6 contains two square planar nickel centres (Niue5f8C=1.907(7), Niue5f8P=2.119(2), Niue5f8O=1.955(5) and 1.919(6) A) with parallel coordination planes (non-bonding Niue5f8Ni=2.865(2) A).

Synthesis and structural characterization of new oxorhenium and oxotechnetium complexes with XN2S-tetradentate semi-rigid ligands (X = O, S, N)

Twelve novel oxo-technetium and oxo-rhenium complexes based on N2S2-, N2SO- or N3S-tetradentate semi-rigid ligands have been synthesised and studied herein. By reacting the ligands with a slight excess of suitable [MO]3+ precursor (ReOCl3(PPh3)2 or [NBu4][99gTcOCl4]), the monoanionic complexes of general formula [MO(Ph-XN2S)]- could be easily produced in high yield. The complexes have been characterized by means of IR, electrospray mass spectrometry, elemental analysis, NMR and conductimetry. The crystal structures of [PPh4][ReO(Ph-ON2S)] 1b and [NBu4][99gTcO(Ph-ON2S)] 1c have been established. The [MO]3+ moiety was coordinated via the two deprotonated amide nitrogens, the oxygen and the terminal sulfur atoms in 1b and 1c. In both compounds, the ON2S coordination set is in the equatorial plane, and the complexes adopted a distorted square-pyramidal geometry with an axial oxo-group. The chemical and structural identity of the different prototypic complexes (rhenium, 99gTc complexes and their corresponding 99mTc radiocomplexes) have been also established by a comparative HPLC study.

Synthesis and physicochemical characterization of oxo and phenylimido Re(V), Re(III) and Ni(II) complexes with the 2-[bis(ethoxyethyl)phosphino]phenolato ligand and derivatives

2-[Bis(ethoxyethyl)phosphino]phenol P1–OH reacts in basic refluxing solvents with ReOCl3(PPh3)2, in a 2/1 molar ratio, to give the green ReOCl(P1–O)2 complex. Structure elucidation by 31P NMR is consistent with a cis-PP “twisted” octahedral complex, which is the preferred conformation on electronic grounds. The complex is unique in toluene while several species were present in ethanol. When the reaction is performed with Re(NPh)Cl3(PPh3)2, a mixture of trans-PP (major) and cis-PP(minor) species in a 3/1 ratio is obtained. These geometric isomers were distinguished by their 2JPP coupling constants. Only cis-PP-Re(NPh)Cl(P1–O)2, less soluble, could be isolated and its molecular structure determined by physicochemical measurements. This is the first example of cis-PP phosphinophenolato complex with the [ReNPh]3+ core, thus illustrating the importance of the steric demand of the phosphine substituent. Reaction of P1–OH with NiCl2 gives Ni(P1–O)2 as an orange oily solid with a cis-PP square planar structure. This structure is the most probable based on the 31P, 13C NMR data.