Javier Borge

On the fitting of model electron densities into EM reconstructions: a reciprocal-space formulation

A fast method for fitting model electron densities into EM reconstructions is presented. The methodology was inspired by the molecular-replacement technique, adapted to take into account phase information and the symmetry imposed during the EM reconstruction. Calculations are performed in reciprocal space, which enables the selection of large volumes of the EM maps, thus avoiding the bias introduced when defining the boundaries of the target density.

Novel ruthenium(II) complexes containing imino- or aminophosphine ligands for catalytic transfer hydrogenation

Five- and six-coordinate ruthenium(II) complexes containing imino- and aminophosphines have been prepared by ligand exchange processes. Thus, reactions of [RuCl2(PPh3)3] with 2-Ph2PC6H4CHNR (R = Ph (1a); 2′,6′-C6H3Me2 (1b); 2′-C6H4OMe (1c)) lead to the chelate iminophosphine complexes [RuCl2(κ2-P,N-2-Ph2PC6H4CHNR)(PPh3)] (R = Ph (3a); 2′,6′-C6H3Me2 (3b)) and [RuCl2(κ3-P,N,O-2-Ph2PC6H4CHN-2′-C6H4OMe)(PPh3)] (3c), respectively. Similarly, reactions with aminophosphine ligands 2-Ph2PC6H4CH2NHR (R = Ph (2a); iPr (2d); (S)-CHMeCy (2e)) afford the 16-electron complexes [RuCl2(κ2-P,N-2-Ph2PC6H4CH2NHR)(PPh3)] (R = Ph (5a); iPr (5d); (S)-CHMeCy (5e)). The iminophosphines 2-Ph2PC6H4CHNR (R = iPr (1d); (S)-CHMeCy (1e)) react with [RuCl2(DMSO)4] to lead to the bis-iminophosphine complexes [RuCl2(κ2-P,N-2-Ph2PC6H4CHNR)2] (R = iPr (4d); (S)-CHMeCy (4e)). The crystal structure of 4d has been determined by X-ray diffraction. Complexes 3a–c, 4d,e and 5a,d,e are active in catalytic transfer hydrogenation of acetophenone. All of them are more efficient than the precursor [RuCl2(PPh3)3].

Chlorophosphines as auxiliary ligands in ruthenium-catalyzed nitrile hydration reactions: application to the preparation of β-ketoamides

The catalytic hydration of nitriles into amides, in water under neutral conditions, has been studied using a series of arene–ruthenium(II) complexes containing commercially available chlorophosphines as auxiliary ligands, i.e. compounds [RuCl2(η6-p-cymene)(PR2Cl)] (R = aryl, heteroaryl or alkyl group). In the reaction medium, the coordinated chlorophosphines readily undergo hydrolysis to generate the corresponding phosphinous acids PR2OH, which are well-known “cooperative” ligands for this catalytic transformation. Among the complexes employed, best results were obtained with [RuCl2(η6-p-cymene){P(4-C6H4F)2Cl}]. Performing the catalytic reactions at 40 °C with 2 mol% of this complex, a large variety of organonitriles could be selectively converted into the corresponding primary amides in high yields and relatively short times. The application of [RuCl2(η6-p-cymene){P(4-C6H4F)2Cl}] in the preparation of synthetically useful β-ketoamides is also presented.

Gold-Catalyzed Intermolecular Formal Insertion of Aryldiazo Esters into Cp−H Bonds of Iron and Ruthenium Metallocenes

The reaction of ferrocene and ruthenocene with aryldiazo acetates in the presence of gold catalysts produced new functionalized metallocenes resulting from a C-H bond functionalization process. This process is believed to proceed through initial decomposition of the diazo component and formation of an electrophilic gold-carbene intermediate, which is subsequently involved in an electrophilic aromatic substitution. The gold-catalyzed functionalization of ruthenocene exhibited a broad scope and a notable functional-group tolerance. Interestingly, the functionalized ferrocene derivatives were found to react with molecular oxygen to yield α-aryl-α-ferrocenyl-α-hydroxyacetates. Adsorption on silica gel was found to be essential for this dioxygen activation/C(sp3 )-H bond functionalization sequence. The methodologies reported herein provide a simple and efficient approach to functionalized metallocene derivatives that are difficult to access through conventional organic functional group transformations.

Allenylidene indenyl ruthenium(II) complexes as sources of highly functionalized alkynyl complexes: synthesis of the first bimetallic derivatives containing a vinylidene–carbene bridge

The alkynylphosphonioruthenium(II) complex [Ru{–CC–C(PMe3)(H)Ph}(PPh3)2(η–C9H7)][PF6] reacts with aldehydes, ketones and phenylisocyanate via a Wittig process to afford either enynyl or keteniminyl complexes; [Ru(CCCPh2)(P-Ph3)2(η-C9H7)][PF6] undergoes regioselective necleophilic attacks at Cγ by the anionic species [M(CO5)C(OMe)CH2]-(M Cr, Mo, W) to yield binuclear alkynyl-carbene complexes [(η-C9H7)(PPh3)2Ru-CC-CPh2-CH2-C(OMe)M(CO)5] which are the precursors of the first vinylidene–carbene bimetallic cationic derivatives [(η-C9H7)(PPh3)2RuCC(H)–CPh2–CH2–C(OMe)M(CO)5]+.

Butadiene dyes based on 3-(dicyanomethylidene)indan-1-one and 1,3-bis(dicyanomethylidene)indane: synthesis, characterization and solvatochromic behaviour

Novel donor–acceptor butadiene chromophores were synthesized by Knoevenagel condensation of different diaryl-substituted enals with 3-(dicyanomethylidene)indan-1-one and 1,3-bis(dicyanomethylidene)indane. The structures of two of these compounds were unambiguously confirmed by means of single-crystal X-ray diffraction. The absorption spectra of these dyes, as well as their solvatochromic behaviour, were studied in detail. In addition, DFT and TD-DFT quantum chemical calculations were performed to assess information regarding the topologies and absolute energies of their frontier molecular orbitals, as well as their absorption spectra.

η5-Indenylruthenium(II) hydride complexes: synthesis and protonation reactions

Hydride complexes [RuH(η5-1,2,3-C9R3R′4)LL′] (R=R′=H, LL′=dppm (1), dppe (2); L=L′=PMe2Ph (3); L=PPh3, L′=PMe3 (4), PMe2 Ph (5), PMePh2 (6); L=CO, L′=PiPr3 (7); R=Me, R′=H, LL′=dppm (8); L=CO, L′=PPh3 (9), PiPr3 (10); R=R′=Me, L=CO, L′=PiPr3 (11)) have been prepared by the reaction of complexes [RuX(η5-1,2,3-C9R3R′4)LL′] (X=Cl, Br) with an excess of NaOMe in methanol (reflux or room temperature). Protonation of the hydride complex [RuH(η5-C9H7)(PPh3)L] (L=PPh3 (12), PMe3 (4)) with HBF4·OEt2 in Et2O yields the dihydride complexes [RuH2(η5-C9H7)(PPh3)L][BF4] (L=PPh3 (13), PMe3 (14)). Crystal structures of [RuH(η5-C9H7)(PPh3)2] (12) and [RuH2(η5-C9H7)(PPh3)2][BF4]·CH2Cl2 (13) have been determined by X-ray crystallography.

Combining image-seeking functions and a subtraction strategy : A vector-space procedure to improve many-body searches in molecular replacement

Many-body searches in molecular replacement are usually carried out sequentially and each step benefits from the structural information obtained in previous rotational and translational stages. In this context, the incorporation of known structural information has proved to enhance the discrimination of a rotation function in Patterson space when many independent molecules have to be located in the asymmetric unit of the crystal cell. This improvement is achieved by subtraction of the contributions of already positioned molecules from the observed Patterson map, which makes the determination of the correct orientation of the remaining molecules easier. The quality of the resultant difference Patterson map is greatly influenced by the application of a bulk-solvent correction to the structure-factor amplitudes of the molecules that are being subtracted. The results obtained in the rotation search benefit both from the availability of high-resolution data and from the combination of the subtraction strategy and the refinement of a great number of the peaks of the rotation function.

OVIONE: a new vector-search rotation-function program for macromolecular crystallography

A computer program (OVIONE) that uses a new vector-search rotation function for crystal-structure determination by the molecular-replacement method has been developed. Image-seeking functions have proved to be useful rotation functions in macromolecular crystallography, provided that some conditions on the statistical parameters of both the crystal and the model Patterson maps are fulfilled. An appropriate selection of the vectors involved in the calculation of the image-seeking functions is crucial for the success of the proposed procedure. This selection relies on certain parameters, a careful analysis of which has been performed in order to establish optimal ranges in which the discrimination of the rotation function is enhanced. Finally, the refinement of the highest peaks of the rotation function is carried out by making use of a simple and quick minimization algorithm.

A new vector-search rotation function: image- seeking functions revisited in macromolecular crystallography

A new rotation function in Patterson space is described. An image-seeking function can be defined as a criterion of fit between the observed Patterson map and a suitable vector set extracted from a specially calculated Patterson map of the search model. The behaviour of image-seeking functions has appeared to be heavily dependent on certain relations between some statistical parameters of both maps. A new algorithm, which carries out the crucial step of selecting the appropriate vector set from the search model, has been established. As a consequence of the combination of these two preceding results, a new vector-search rotation function has been proposed and tested.