Antonio Romerosa

Coordination chemistry and functionalization of white phosphorus via transition metal complexes

The chemistry of phosphorus is nowadays rivaling that of carbon in terms of complexity and diversity. This tutorial review highlights the state-of-the-art in the field of metal-mediated activation and functionalization of white phosphorus. Particular attention is given to an illustration of the coordination abilities of the intact molecule as well as the disaggregating and reaggregating metal-mediated processes resulting in different polyphosphorus ligands from P(1) to P(12). The metal-promoted P-C and P-H bond forming processes are also reviewed showing that an ecoefficient catalytic protocol for transforming P(4) into high value organophosphorus compounds is a concrete possibility for chemical companies. This tutorial review deals with the activation and functionalization of white phosphorus in the coordination sphere of transition metal complexes. Particular attention is given to the coordination abilities of the intact molecule as well as to the disaggregating and reaggregating metal-mediated processes yielding various polyphosphorus ligands from P(1) to P(12). The metal-promoted processes for P-C and P-H bond formation are also reviewed showing that an ecoefficient catalytic protocol for transforming P(4) into high value organophosphorus compounds offers good opportunities for chemical companies.

Structure and magnetic properties of a syn-anti carboxylate bridged linear trinuclear copper(II) complex with ferromagnetic exchange interaction

Abstract The synthesis, crystal structure and magnetic properties are reported for the trinuclear compound [Cu(H2O)4{Cu(HL)(H2O)(ClO4)}2][ClO4]2·2H2O, where HL is the monodeprotonated form of 6-methylamino-1,3-dimethyl-5-[(2′-carboxyphenyl)azo]uracil. The compound crystallizes in the triclinic system, space0 group P 1 , with cell constants a=7.824(3), b=12.278(3), c=13.705(9) A, α=104.34(3), β=91.80(3), γ=103.37(5)° and Z=1. The structure was solved and refined to R=0.071 (Rw=0.064). The structure consists of trinuclear [Cu(H2O)4{Cu(HL)(H2O)(ClO4)}2]2+ cations, non-coordinated perchlorate anions and crystal water molecules, held together by a network of hydrogen bonds. The central copper is in an elongated octahedral CuO6 chromophore and the terminal copper atoms in distorted square-pyramidal CuNO4 chromophores. Adjacent copper atoms are linked by carboxylate groups in a syn-anti conformation. From the magnetic susceptibility measurements, the complex is found to exhibit weak ferromagnetic interaction between nearest-neighbour copper(II) ions. The magnitude and nature of the exchange coupling are discussed on the basis of the structural data.

Metal-mediated degradation and reaggregation of white phosphorus

A critical survey of the coordination chemistry of white phosphorus illustrating the metal-mediated degradation of the P4 tetrahedron is presented. The underlying principles to account for the activation and stepwise fragmentation of this molecule in the presence of transition metal complexes are presented with emphasis given to mechanistic aspects. A collection of 31P-NMR spectral data for the known polyphosphorus Px compounds (x ≤ 4) is also presented and briefly commented.

A water soluble diruthenium-gold organometallic microgel.

Selection of the combination of metal, ligand set, and spacer groups that are most appropriate to form a coordination complex with a desired function are of paramount importance in supramolecular chemistry. In particular, the establishment of reproducible methods to accomplish controlled selforganization of molecules to form polymers and homoor heterometallic coordination aggregates is an important field of research. Although important advances have already been made, few metallopolymers, which are one of the most exciting classes of functional materials, are water soluble. An important example of a water-soluble polymer is the polyferrocenylsilane-b-polyaminomethacrylate copolymer described by Manners and co-workers, as part of their ongoing study on metallocene-based polymers. Recent examples also include the water-soluble metallopolymer obtained by reaction of bipyridyl-appended poly(p-phenyleneethynylene) (PPEs) with metal ions in organic and aqueous solution. Other examples of ligands that afford coordination polymers with various topologies and applications are ferrocenyl groups bearing bipyridine (bpy) or carboxylate moieties. A recent example of a non-water-soluble multimetallic polymer is [Sm(H2O)5][Ru2(bpy)2(CN)7], in which the CN ligands bridge the samarium and ruthenium metal centers. The first air-stable water-soluble multimetallic polymer that includes mixed P,N ligands as metal-coordinating spacers has been recently reported by us. This heterobimetallic complex is based on two metal-containing moieties, [CpRu] (Cp= cyclopentadienyl) and [AgCl2] , and is bridged by the cagelike water-soluble monodentate phosphine 1,3,5-triaza-7phosphaadamantane (pta) in an unprecedented P,N coordination mode. More recently, the synthesis of silver coordination polymers containing pta bridging molecules in a tridentate P,N,N’ coordination mode has been reported and several examples of pta N coordination have been presented. Therefore the pta molecule could be an excellent ligand from which to obtain water-soluble Ru–Au polymers which could have interesting and useful properties for a variety of applications such as magnetism, nonlinear optics, electrocatalysis, photocatalysis, photovoltaic, template formation of ordered networks, advanced electrode materials, and conjugated coordination polymers. Herein, we describe the first water-soluble, air-stable heterobimetallic polymeric structure based on two metalcontaining moieties [CpRuCNRuCp] and [Au(CN)4] , bridged by pta in the P,N coordination mode. Interestingly, this complex display gel-like properties in water, specifically a thermally controlled volume transition. To the best of our knowledge, this is the first example of an coordination polymer network that is sensitive to its environment. The physical and chemical properties of this complex make it a promising material for industrial and biological applications, for example, smart catalysis, drug delivery, or chemical sensing. The first strategy we attempted to obtain a water soluble Ru–Au polymer was similar to that used for the synthesis of [{CpRu(pta)2(DMSO-kS)}{AgCl2}]1. [8] The complex [CpRuCl(pta)2] (1) was reacted in a straightforward manner with AuCl3 in water, EtOH, and DMSO, and in the presence of NaBF4 and NaCF3SO3. This resulted in the swift formation of a stoichiometric amount of metallic gold. A second strategy, in which the [Au(CN)4] moiety (which is very stable under a wide variety of conditions) was used, was then tested. The reaction of 1 with K[Au(CN)4] led to the partial reduction of gold together with the formation of several new species. A careful analysis of the reaction products suggested that the presence of the chloride ion in 1 could give rise to the formation of unstable gold species which finally decompose to metallic gold. To avoid the presence of the chloride ion in the reaction, the complex [RuCp(CN)(pta)2] (2) was prepared by substitution of 1 with KCN at room temperature in water (Scheme 1). Slow crystallization of a diluted H2O solution of [Ru(CNkC)Cp(pta)2] (2) in air give colorless crystals suitable for Xray diffraction. The X-ray crystal structure of complex 2 shows that it is a mononuclear complex in the solid state and is similar to 1, except that the chloride ligand has been

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.

Macrocycles incorporating closo- and nido-carbaborane cages: molecular structure of 1,2-(3′-oxapentane-1′,5′-dithiolato-SS′)-1′,2′-dicarba-closo-dodecaborane

Reaction of 1,2-dimercapto-1,2-dicarba-closo-dodecaborane under basic conditions with appropriate dihalogenated organic compounds results in the formation of macrocycles incorporating 7,8-dicarbaundecaborate or 1,2-dicarba-closo-dodecaborane units. Polymers are obviated by using high dilution. The crystal structure of 1,2-(3′-oxapentane-1′,5′-dithiolato-SS′)-1′,2′-dicarba-closo-dodecaborane has been determined. It crystallizes in space group P21/a with four formula units in a cell of dimensions a= 11.708(2), b= 10.209(3), c= 12.613(3)A, and β= 109.04(2)°.

Metal-Assisted P−H Bond Formation: A Step towards the Hydrogenation of White Phosphorus

An overview of the chemistry of transition metal complexes containing P−H bonds is presented. Central to this microreview are those compounds in which the P−H bond is assembled by reactions entailing the transfer of one or more hydrogen atoms to white phosphorus or to Px fragments resulting from P4 activation and degradation within the coordination sphere of a transition metal complex. The relevance of these processes to the as yet unaccomplished hydrogenation of white phosphorus is briefly discussed.

Synthesis and Structural Characterization of (Carbene)ruthenium Complexes Binding Nucleobases

The new (carbene)ruthenium(II) nucleobase derivatives fac,cis-[(PNP)RuCl{C(NHC4H3N2O2)(CH2Ph)}]Cl (5) and fac,cis-[(PNP)RuCl{C(NHC5H3N4)(CH2Ph)}]Cl (6) [PNP = CH3CH2CH2N(CH2CH2PPh2)2] were synthesised by treating (vinylidene)ruthenium(II) complex fac,cis-[(PNP)RuCl2{C=C(H)Ph}] (1) with 5-aminouracil or adenine, respectively. Both complexes were characterized by spectroscopic techniques (IR and NMR) and elemental analyses, which confirmed the formation of the aminocarbene moieties incorporating 1 equiv. of the nucleobase in the complex framework. Crystal and molecular structure determination by X-ray diffraction analysis of the uracil derivative 5 revealed a very unusual O-coordination of the exocyclic C=O group on the C(4) atom of the uracil ring to the ruthenium atom leading to an unprecedented six-membered aminocarbene metallacycle. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Dinuclear copper(II) complexes containing nitroso-oximato bridges: two different copper(II)-bridging entities from the same precursor

The complexes [Cu(μ-L)Cu(bipy)(EtOH)](ClO4)2 2a and [Cu(μ-1L)Cu(bipy)(H2O)](ClO4)2·H2O 2b [where H2L = N,N′-bis(1,3-dimethyl-5-nitrosopyrimidine-2,4-(1H,3H)-dion-6-yl)propylenediamine; H21L arises from H2L by elimination of a CO molecule from one of the pyrimidine rings] have been obtained from the reaction of the precursor [Cu(μ-HL)Cu(H2O)2(CH3CH2OH)](ClO4)3 1 with bipy and Cu(ClO4)2 · 6H2O, respectively. The structures of 2a and 2b have been solved by X-ray crystallographic methods. The structure of 2a is made up of [Cu(μ-L)Cu(bipy)(EtOH)]2+ cations and two semi coordinated perchlorate anions. The [Cu(I)L] fragment coordinates to the external Cu(2) ion through the two deprotonated oximate oxygens to afford a dinuclear structure with double syn-syn nitroso-oximate bridge and an intramolecular CuCu distance of 3.731(1) A. The Cu(1) exhibits a CuN4O2 pseudoctahedral coordination polyhedron whereas the geometry around the Cu(2) ion is distorted square-pyramidal CuN2O2O. The structure of 2b consists of [Cu(μ-1L)Cu(bipy)(H2O)]2+ cations, two perchlorate anions and one lattice water molecule. The coordination of the [Cu(1L)] unit to the external Cu(2) ion takes place through the two nitroso-oximate groups, one of them disordered on two sets of crystallographic positions, one with a 63% occupancy and the other with a 37% occupancy. The intramolecular Cu(l)Cu(2) distance is 3.655(3) A. The Cu(l) occupying the inner site of the 1L2− ligand exhibits a 4+1 CuN4O (63%) [CuN3O2(37%)] coordination environment whereas the Cu(2) atom is in a distorted square-pyramidal CuN2O3(63%)[CuN3O2(37%)] environment. The dinuclear fragments of 2a and 2b are almost planar with dihedral angles between the mean basal coordination planes of 4.1(2)° and 4.6°, respectively. Both 2a and 2b are diamagnetic at room temperature, so that J < −1000 cm−1. The structural and magnetic data for these complexes have been compared with those of similar compounds, but no correlation between the magnitude of the exchange interaction and the degree of deviation from planarity is evident. In view of this and to rationalize the influence of the distortion from planarity on the magnetic properties in oximate-bridged complexes, MO Extended Huckel calculations have been performed.

exo-Dithio and monothio carborane derivatives: a mechanism for their partial degradation. Molecular structure of tetramethylammonium 7,8-(3′,6′,9′-trioxaundecane-1′, 11′-dithiolato-SS′)-7,8-dicarba-nido-undecaborate

Abstract The reaction of 1,2-dithiol-o-carborane, under basic conditions, with appropriate organic dihalogenated compounds results in the formation of macrocycles incorporating 7,8-dicarba-nido-undecaborate or 1,2- dicarba-closo-dodecaborane units. The synthesis of some non-cyclic dicarborane compounds containing only one sulfur per cage directly bonded to the cluster is described. On the basis of the different behavior of the dithiolato compounds versus the monothiolato, a mechanism that explains the formation of partially degraded and non-degraded compounds is proposed. The molecular structure of tetramethylammonium 7,8-(3′,6′,9′-trioxaundecane-1′,11′ -dithiolato-SS′)-dicarba-nido-undecaborate has been determined. It crystallizes in space group P21/c with 4 formula units per cell. The cell dimensions are a=14.058(7), b=7.536(2), c=22.980(9) A, β=99.41°.