Claudio Mendicute-Fierro

Efficient hydridoirida-β-diketone-catalyzed hydrolysis of ammonia- or amine-boranes for hydrogen generation in air

The dihydridoirida-β-diketone [IrH2{(PPh2(o-C6H4CO))2H}] (2) has been used as a homogeneous catalyst for the hydrolysis of ammonia- or amine-boranes to generate up to 3 equivalents of hydrogen in the presence of air. When using 0.5 mol% loading of 2, dimethylamine-borane is hydrolysed completely within 8 min at 30 °C and maintains its activity in consecutive runs. Ammonia-borane or tert-butylamine-borane is hydrolysed completely within 32 or 25 min respectively. Triethylamine-borane fails to be hydrolysed. Kinetic studies suggest a sequence of two consecutive first-order reactions, in which an intermediate builds up and finally falls, with the first step being the rate controlling step. ΔH1(‡) are in the range 65-85 kJ mol(-1) and negative values of ΔS1(‡) are obtained. A multinuclear NMR study of the catalyzed reaction shows the formation of a resting state (A) of the active catalyst proposed to be of the hydridodiacyl type [IrH(PPh2(o-C6H4CO))2(solvent)] with a hydride trans to the acyl group. In the absence of substrate a dormant species (B) is formed. By the reaction of hydridoirida-β-diketones with ammonia, the hydridoirida-β-ketoimine [IrHCl{(PPh2(o-C6H4CO))(PPh2(o-C6H4CNH))H}] (3) and the hydridobis(acylphosphane)aminoiridium(III) complex [IrH(PPh2(o-C6H4CO))2(NH3)] (4), with a hydride trans to phosphane, are formed. Aromatic amines such as aniline or anisidines afford cationic [IrH{(PPh2(o-C6H4CO))2H}(C6H4RNH2)]ClO4 (R = H (6); p-MeO (7); o-MeO (8)) hydridoirida-β-diketones with a coordinated amine group trans to the hydride. The dormant species B is proposed to be of the hydridobis(acylphosphine)aminoiridium(III) type with a hydride trans to the amine group.

Effect of π–π stacking interactions on the emission properties of cadmium metal–organic frameworks based on 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene

Five multidimensional cadmium metal–organic frameworks based on the luminescent 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene linker and flexible dicarboxylate ligands have been synthesized by conventional routes. These MOFs show fascinating structures and display, in the solid state and at room temperature, intense and hypsochromic photoluminescence properties when packed as a 3D network and bathochromic photoluminescence properties when arranged as 2D networks, as compared to the emission properties of the free luminescent 4-bpdb ligand. DFT calculations have revealed the establishment of destabilizing π–π stacking interactions between pyridyl rings of neighbouring 4-bpdb aromatic linkers on the 3D networks synthesized, responsible for the unexpected hypsochromic emission. The absence of π–π stacking interactions in the 2D MOFs yields the expected bathochromic photoluminescence arising from metal coordination with the aromatic ligand.

A pentacoordinated norbornenyl-acyl-rhodium(III) complex as a likely intermediate in the catalytic hydroacylation of norbornadiene

[RhCl(NCO)(nbyl)(PR3)] (nbyl = σ-norbornenyl; NCO = quinoline-8-acyl; R = p-F-C6H4) (1) has been synthesized by the reaction of [Rh(nbd)Cl]2 (nbd = norbornadiene) with 2 equivalents of NCHO (quinoline-8-carbaldehyde) and 2 equivalents of PR3. Compound 1 has been fully characterized in solution and also in the solid state by X-ray diffraction. Compound 1 shows low stability in solution and undergoes slow ring closure isomerization to [RhCl(NCO)(ntyl)(PR3)] (ntyl = σ-nortricyclyl) (2) after 12 hours. Reaction of 1 with an extra equivalent of aldehyde (NCHO) and PR3 led to the formation of [RhCl(H)(NCO)(PR3)2] (3) and an equivalent of ketone, which is a hydroacylation product. The catalytic activity of 3 in the hydroacylation of nbd with NCHO is reported as well as the catalytic activity of compound 1. Compounds 1 and 3 are proposed as intermediate species in the catalytic hydroacylation of norbornadiene with NCHO.

Secondary Oxide Phosphines to Promote Tandem Acyl–Alkyl Coupling/Hydrogen Transfer to Afford (Hydroxyalkyl)rhodium Complexes. Theoretical and Experimental Studies

Acyl(σ-norbornenyl)rhodium(III) dimer [Rh(μ-Cl)(C9H6NCO)(C7H9)L]2 (1) (C7H9 = σ-norbornenyl; L = 4-picoline, isoquinoline) reacts with diphenylphosphine oxide (SPO) to undergo a one-pot reaction involving (i) cleavage of the chloride bridges and coordination of the phosphine, (ii) C-C bond coupling between acyl and norbornenyl in a 18e species, and (iii) ligand-assisted outer-sphere O(P)-to-O(C) hydrogen transfer, to afford mononuclear 16e species [RhCl{(C9H6NC(O)C7H9)(Ph2PO)H}(L)] (2) containing a quinolinyl-(norbornenylhydroxyalkyl) fragment hydrogen-bonded to a κ1- P-phosphinite ligand. Pentacoordinated 2, which adopt a distorted trigonal bipyramidal structure, are kinetic reaction products that transform into the thermodynamic favored isomers 3. Structures 3 contain an unusual weak η1-C anagostic interaction involving the rhodium atom and one carbon atom of the olefinic C-H bond of the norbornenyl substituent in the chelating quinolinyl-hydroxyalkyl moiety. Their structure can be described as pseudoctahedral, through a 5 + 1 coordination, with the anagostic interaction in a trans disposition with respect to the phosphorus atom of the phosphinite ligand. Complexes were characterized in solution by NMR spectroscopy and electrospray ionization mass spectrometry. Complex [RhCl{(C9H6NC(O)C7H9)(Ph2PO)H}(4-picoline)] (3a) was also identified by X-ray diffraction. Density functional theory calculations confirm the proposed structures by a plausible set of mechanisms that accounts for the 1 (monomer) → 2 → 3 transformation. Lowest-energy pathways involve reductive elimination of quinolinylnorbornenylketone, still coordinated in the rhodium(I) species thus formed, followed by O-to-O hydrogen transfer from κ1- P-SPO to the sp3 hybridized carbonyl group (formal alkoxide) avoiding the otherwise expected classical release of ketone. Theoretical 13C NMR studies also confirm the experimental spectral data for the considered structures.

CCDC 1475418: Experimental Crystal Structure Determination

Related Article: Itziar Zumeta, Claudio Mendicute-Fierro, Itxaso Bustos, Miguel A. Huertos, Antonio Rodriguez-Dieguez, Jose M. Seco, Eider San Sebastian, and Maria A. Garralda|2016|Inorg.Chem.|55|10284|doi:10.1021/acs.inorgchem.6b01550

CCDC 1475416: Experimental Crystal Structure Determination

Related Article: Itziar Zumeta, Claudio Mendicute-Fierro, Itxaso Bustos, Miguel A. Huertos, Antonio Rodriguez-Dieguez, Jose M. Seco, Eider San Sebastian, and Maria A. Garralda|2016|Inorg.Chem.|55|10284|doi:10.1021/acs.inorgchem.6b01550

CCDC 1475415: Experimental Crystal Structure Determination

Related Article: Itziar Zumeta, Claudio Mendicute-Fierro, Itxaso Bustos, Miguel A. Huertos, Antonio Rodriguez-Dieguez, Jose M. Seco, Eider San Sebastian, and Maria A. Garralda|2016|Inorg.Chem.|55|10284|doi:10.1021/acs.inorgchem.6b01550

2D-cadmium MOF and gismondine-like zinc coordination network based on the N-(2-tetrazolethyl)-4′-glycine linker

This work was supported by the MEC of Spain (Project CTQ2011-24478) and the Junta de Andalucia (FQM-1484). D. F.-J. thanks the Royal Society for a University Research Fellowship.