Juan Granifo

Mononuclear and binuclear rhenium(I) carbonyl complexes of 2,4,6-tris(2-pyridyl)-1,3,5-triazine (TPT), [{ReCl(CO)3}n(TPT)] (n=1, 2), and the formation of mixed-metal compounds with Re–TPT–M (M=MnII, CoII, CuII) bonds

Abstract The novel mononuclear complex [ReCl(CO) 3 (TPT)] has been isolated where the triazine ligand is acting in a didentate chelate mode. The metalloligand properties of this Re(I) complex were demonstrated when it reacts didentally either with the {ReCl(CO) 3 } fragment or with the [M(hfac) 2 ] (M=Mn, Co, Cu; hfac=hexafluoroacetylacetonate ion) complexes, producing the homobinuclear [{ReCl(CO) 3 } 2 (TPT)] and the heterobimetallic [(CO) 3 ClRe(TPT)M(hfac) 2 ] substances, respectively. In methanol solution the binuclear Re–TPT–Re complex forms the [{ReCl(CO) 3 } 2 (TPT)]·MeOH complex, where a methoxide group seems to be interacting with the acidic triazine ring and the nitrogen atom of the uncoordinated pyridyl group is protonated. In general, the studies in solution of the dirhenium Re–TPT–Re complex show evidence of its interaction with the solvent molecules apparently in an acid-base fashion. On the other hand, the mixed-metal Re–TPT–M derivatives show dissociation reactions in solution generating the parent mononuclear [ReCl(CO) 3 (TPT)] compound and the [M(hfac) 2 ] complexes. The systems under study were characterized through IR, 1 H NMR and electronic spectroscopy, electrochemical and magnetic moment measurements.

Coordination mode of some polypyridyl ligands towards the platinum(II) complexes [Pt(dppf)(H2O)2](CF3SO3)2 (dppf=1,1′-bis(diphenylphosphino)ferrocene) and [Pt(Me2SO)2Cl2]. Crystal structure of the seven-membered chelate ring complex [Pt(dpq)Cl2] (dpq=2,3-di(2-pyridyl)quinoxaline)

Abstract A series of novel platinum(II) complexes were isolated through the reaction of the polypyridyl ligands 2,3,7,8-tetra(2-pyridyl)pyrazino[2,3-g]quinoxaline (tpq), 2,3-di(2-pyridyl)pyrazine (dpp), 2,3-di(2-pyridyl)quinoxaline (dpq) and 6,7-dimethyl-2,3-di(2-pyridyl)quinoxaline (ddpq) with the heterobimetallic complex [Pt(dppf)(H2O)2](CF3SO3)2 or with the dimethyl sulfoxide complex [Pt(Me2SO)2Cl2]. The di-platinum complex [{Pt(dppf)}2(tpq)](CF3SO3)4 and the mono-platinum compounds [Pt(dppf)(L)](CF3SO3)2 (L=dpp, ddpq) and [Pt(L)Cl2] (L=dpq, ddpq) were synthesized. As shown by 1H NMR spectroscopy, in these complexes the bridging tpq and the mononucleating ligands dpp, dpq and ddpq present an uncommon bidentate chelate mode; they are bonded to the Pt(II) centres only by the means of their pyridyl nitrogen atoms. This behaviour was corroborated through the X-ray crystallographic study of the [Pt(dpq)Cl2] derivative. The redox properties of the three new dppf-based complexes, in dichloromethane solution, show in all cases that they undergo ferrocene-based (dppf) oxidations and that the primary cathodic processes are tpq-centered in the tpq complex and platinum(II)-centered in the dpp and ddpq complexes.

Synthesis and dynamic NMR studies of stereochemical non-rigidity in rhenium(I) complexes of 2,6-bis[1-(phenylimino)ethyl]pyridine derivatives

Abstract The complexes fac -[ReCl(CO) 3 L] [L= ortho or para substituted methyl or t butyl aromatic derivatives of 2,6-bis[1-(phenylimino)ethyl]pyridine (BIP)] were synthesised. In solution all complexes exist as bis-imine E , E and E,Z isomers, with the former greatly predominating (>85% in most cases). 1,4-Metallotropic shifts of the ReCl(CO) 3 moiety between the ligand N donor pairs occur in all cases. In the 1 H NMR spectra of the methyl- and the para - t Bu aromatic derivatives of BIP these shifts were detected as exchange between equivalent E , E forms of the complexes. In the case of the ortho - t Bu derivative, where the E , Z -isomer was more in evidence (21% at 303 K), E , E ⇌ E , Z isomerisation occurs rather more readily than the accompanying metallotropic shifts. Rates and activation energies for the detected dynamic processes were based on NMR bandshape analysis. The results indicated that Me and t Bu substitution of the phenyl rings in BIP had a negligible effect on the Re I N 1,4-metallotropic shifts, whereas ortho substitution of the rings, particularly by t Bu had a considerable influence on the relative proportions of E,E and E,Z conformers, presumably because of steric effects.

Synthesis and characterization of [ReCl(CO)3(L)] [L = 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine (dppt) or 3,5,6-tri(2-pyridyl)-1,2,4-triazine (tpt)] and the bidentate coordination of the metalloligand [ReCl(CO)3(tpt)] to [M(hfac)2] (M = Mn, Fe, Co, Ni, Cu, Zn; hfac = hexafluoroacetylacetonate ion)_

Abstract The synthesis and characterization of the novel mononuclear species [ReCl(CO)3(L)], where L is 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine (dppt) or 3,5,6-tri(2-pyridyl)-1,2,4-triazine (tpt), is reported. The coordination mode of the dppt and tpt ligands to the ReCl(CO)3 fragment apparently occurs through a pyridyl nitrogen and a triazine nitrogen. In addition, the tpt based monomer [ReCl(CO)3(tpt)] behaves as a bidentate metalloligand, reacting with the [M(hfac)2] (M = Mn, Fe, Co, Ni, Cu, Zn; hfac = hexafluoroacetylacetonate ion) complexes to produce the heterobimetallic substances [(CO)3ClRe(tpt)M(hfac)2]. In these RetptM complexes the tptM binding is atypical, since only the two free pyridyl nitrogen atoms of the chelating [ReCl(CO)3(tpt)] complex are involved. The new compounds were characterized by IR, 1H NMR and electronic spectroscopy, electrochemical and magnetic moment measurements.

Synthesis of the mononuclear Mo(CO)4(L) [L = 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine (dppt) or 3,5,6-tri(2-pyridyl)-1,2,4-triazine (tpt)] complexes and the chelating action of the Mo(CO)4(tpt) derivative towards M(hfac)2 (M = Mn, Fe, Co, Ni, Cu Zn; hfac = hexafluoracetylacetonate ion)

Abstract The novel mononuclear tetracarbonyl complexes Mo(CO) 4 (L), where L is 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine (dppt) or 3,5,6-tri(2-pyridyl)-1,2,4-triazine (tpt), have been synthesized and characterized. The ligands dppt and tpt seem to be coordinated to the metal centre via a pyridyl nitrogen and a triazine nitrogen. The tpt complex Mo(CO) 4 (tpt) is effective as a bidentate chelating system toward the acidic M(hfac) 2 (M = Mn, Fe, Co, Ni, Cu, Zn) species producing the bimetallic (CO) 4 MO(tpt)M(hfac) 2 compounds. In these Mo -tpt-M products the ligating Mo(CO) 4 (tpt) complex is coordinated in an unusual mode involving only pyridyl nitrogen atoms. The new substances were characterized by IR, 1 H NMR, electronic spectroscopy, electrochemical and magnetic moment measurements.

Reactivity of [M(CO)3(NN)(thioureas)] (M = Mo, W; NN = 2,2′bipyridine, 1,10-phenanthroline) complexes towards systems with mercury-halides bonds. Trimetallic compounds with XMHgM′X (M′ = Mo, W; X = Cl, Br, I) bondings

Abstract New heterotrimetallic complexes were isolated by reaction of M(CO)3(NN)L (M = Mo, W; NN = bipy, phen; L = thioureas) either with HgX2 (X = Cl, Br, I) giving complexes of the formula [M(CO)3(NN)(X)]2Hg or with M′(CO)3(NN′)(Cl)(HgCl) (M′ = Mo, W; NN′ = bipy, phen) producing compounds of the type (Cl)(NN)(CO)3MHgM′(CO)3(NN′)(Cl). These new photosensitive substances were characterized through IR spectroscopy and conductivity measurements. Structures involving XMHgM′X bonding are proposed and the reactions are discussed in terms of an insertion of the fragment M(CO)3(NN) into the HgX bonds.

Stereoisomers of palladium(II) complexes with the dipyridyl ligands 2,3-di(2-pyridyl)pyrazine (dpp), 2,3-di(2-pyridyl)quinoxaline (dpq) and 6,7-dimethyl-2,3-di(2-pyridyl)quinoxaline (ddpq). Crystal structure of [Pd(dpq)2](PF6)2

Abstract A solid-state and solution study to characterize the possible configurations of the [Pd(L)2]2+ cations (L=dpp, dpq, ddpq) has been carried out. To accomplish this objective the homoleptic complexes [Pd(L)2](hfac)2 (L=dpp, dpq, ddpq; hfac=hexafluoroacetylacetonate ion) were isolated. The syntheses were performed in diethyl ether by reacting [Pd(hfac)2] with a two molar equivalent of the respective L ligand. Besides, X-ray quality crystals were obtained by metathesis with NH4PF6 to derive the hexafluorophosphate species [Pd(dpq)2](PF6)2. The X-ray crystallographic study shows that the coordination sphere of the [Pd(dpq)2]2+ cation is square planar and that the bidentate chelating dpq ligands are linked via their N-pyridine atoms. Furthermore, the cation structure reveals an intramolecular π–π stacking between the two quinoxaline rings in a ‘pincer-like’ configuration. In CDCl3 solution, the 1H NMR spectra of the [Pd(L)2](hfac)2 complexes permit to infer the presence of a mixture of two isomeric forms with different populations. The results suggest that the predominant form being that of the solid-state ‘pincer-like’. For the less abundant species a configuration with the quinoxaline groups (dpq, ddpq) or pyrazine groups (dpp) in opposite side respect to the plane of the Pd(II) centre, ‘step-like’, is suggested. The preponderance of the ‘pincer-like’ configuration was attributed to the influence of the aromatic π–π stacking interactions.

Reactions of pentacarbonyliron(0) and hexacarbonylmolybdenum(0) complexes with thiocyanogen

The reactions of pentacarbonyliron(0) and hexacarbonylmolybdenum(0) with thiocyanogen yield the polymeric complexes [Fe(CO)2(SCN)2] and [Mo(CO)4(SCN)2] respectively. The complexes are thermally and hydrolytically unstable, I.r. spectra are reported.

Coordination of a polyfunctional cyclic ligand containing a PP bond to the fragment [Mo(CO)3(NN)] (NN = 2,2′-bipyridine, 1,10-phenanthroline). Spectroscopic and electrochemical characterization

Abstract The reaction of 1,3,4,6-tetramethyl-1H,4H-1,3,4,6-tetraaza-3a, 6a-diphosphapentalen-2,5(3H,6H)-dithion-3a-sulphide (TDP) with the derivatives of metal carbonyls [Mo(CO) 3 (NN)(CH 3 CN)] (NN = 2,2′-bipyridine, 1, 10-phenanthroline) leads to fac -Mo(CO) 3 (NN)(TDP) complexes with the ligand coordinated through the trivalent phosphorus atom. The IR and visible spectra of the new complexes as well as their electrochemical and general properties are discussed.

Synthesis of mono- and binuclear [{Mo(CO)3L}n(dpq)] [n = 1,2; L = CO, MeCN, PPh3; dpq = 2,3-bis(2-pyridyl)quinoxaline] complexes and heterobimetallic adduct formation with hexafluoroacetylacetonatecobalt(II)

Abstract The new compounds [{Mo(CO) 4 } n (dpq)] [ n = 1,2; dpq = 2,3-bis(2-pyridyl) quinoxaline] on refluxing in MeCN produce the acetonitrile complexes [{Mo(CO) 3 (NCMe)} n (dpq)] ( n = 1,2). These acetonitrile derivatives behave as precursors for the tricarbonyl-based fragments [{Mo(CO) 3 } n (dpq)] ( n = 1,2); they react in CH 2 Cl 2 at room temperature with PPh 3 to afford the [{Mo(CO) 3 }(PPh 3 ) n (dpq)] ( n = 1,2) complexes. In addition, the ligating properties of the novel mononuclear products [Mo(CO) 4 (dpq)] and [Mo(CO) 3 (PPh 3 )(dpq)] towards [Co(hfacac) 2 ] are also reported. The new substances were characterized by IR and electronic spectroscopy.