• I. Reviejo, J. Vinueza, J. Ramos, M. E. G. Mosquera, V. Tabernero, G. Jiménez
    Stereospecific Synthesis of Chiral Titanium Complexes Bearing a Bifunctionalized Cyclopentadienyl-Terpenoid Ligand Derived from α-Pinene, Organometallics, 2021, DOI: 10.1021/acs.organomet.1c00421
  • S. Ghosh, G. Amariei, M. E. G. Mosquera, R. Rosal
    Conjugated Polymer Nanostructures Displaying Highly Photoactivated Antimicrobial and Antibiofilm Functionalities, J. Mater. Chem. B, 2021, 9, 4390-4399, DOI: 10.1039/D1TB00469G
  • M. E. G. Mosquera, G. Jiménez, V. Tabernero, J. Vinueza-Vaca, C. García-Estrada, K. Kosalková, A. Sola-Landa, B. Monje, C. Acosta, R. Alonso, M. Á. Valera
    Terpenes and Terpenoids: Building Blocks to Produce Biopolymers, Sustain. Chem., 2021, 2, 467-492, DOI: 10.3390/suschem2030026
  • M. Palenzuela, L. Valenzuela, G. Amariei, J. F. Vega, M. E. G. Mosquera, R. Rosal
    Poly(glycidyl methacrylate) Macromolecular Assemblies as Biocompatible Nanocarrier for the Antimicrobial Lysozyme, Int. J. Pharm., 2021, 603, 120695, DOI: 10.1016/j.ijpharm.2021.120695
  • L. Álvarez-Miguel, J. Damián Burgoa, M. E. G. Mosquera, A. Hamilton, C. J. Whiteoak
    Catalytic Formation of Cyclic Carbonates using Gallium Aminotrisphenolate Compounds and Comparison to their Aluminium Congeners: A Combined Experimental and Computational Study, ChemCatChem., 2021, DOI: 10.1002/cctc.202100910
  • S. Ghosh, G. Amariei, M. E. G. Mosquera, R. Rosal
    Polymeric Ruthenium Precursor as a Photoactivated Antimicrobial Agent, J. Hazard. Mater., 2021, 402, 123788, DOI: 10.1016/j.jhazmat.2020.123788
  • V. Sessini, B. Haseeb, A. Boldizar, G. Lo Re
    Sustainable Pathway Towards Large Scale Melt Processing of the New Generation of Renewable Cellulose–polyamide Composites, RSC Advances, 2021, 11, 637-656, DOI: 10.1039/D0RA07141B
  • E. L. Henly, K. Norris, K. Rawson, N. Zoulias, L. Jaques, P. G. Chirila, M. Kadirvel, C. J. Whiteoak, T. J. Smith, M. M. Lacey, S. Forbes.
    Impact of Long-term Quorum Sensing Inhibition on Uropathogenic Escherichia Coli, J. Antimicrob. Chemother., 2021, 76, 909-919, DOI: 10.1093/jac/dkaa517
  • A. Hamilton, C. J. Whiteoak
    Applied Organometallics: Cp*Co(III)-catalysed C–H Functionalisation as a Maturing Tool for the Synthesis of Heterocyclic Compounds, Organomet. Chem., 2021, 43, 186-228, DOI: 10.1039/9781788017077-00186
  • M. Palenzuela, D. Sánchez-Roa, V. Sessini, J. Damián, M. E. G. Mosquera
    Polymerization of Terpenes and Terpenoids using Metal Catalysts, Adv. Organomet. Chem., 2021, 75, 55-93, DOI: 10.1016/bs.adomc.2021.01.004


  • M. Mateos, J. Vinueza, M. E. G. Mosquera, V. Tabernero, T. Cuenca, G. Jimenez
    Cyclopentadienyl-silsesquioxane Titanium Compounds as Suitable Candidates for Immobilization on Silica-based Supports, Inorganica Chim. Acta, 2020, 501, 119275, DOI: 10.1016/j.ica.2019.119275
  • F. M. García-Valle, T. Cuenca, M. E. G. Mosquera, S. Milione, J. Cano
    Ring-Opening Polymerization (ROP) of Cyclic Esters by a Versatile Aluminum Diphenoxyimine Complex: From Polylactide to Random Copolymers, Eur. Polym. J., 2020, 125, 109527, DOI: 10.1016/j.eurpolymj.2020.109527
  • A. M. Londaitsbehere, M. Sudupe, M. E. G. Mosquera, T. Cuenca, J. Cano
    MMA Polymerization with Group 4 Alkyl-Free 14-Electron d0 Species, Eur. J. Inorg. Chem., 2020, 17, 1589-1595, DOI: 10.1002/ejic.202000052
  • M. E. G. Mosquera, S. Dortez, F. Fernandez-Palacio, J. Damian, C. Gaiteiro, J. Ramos, P. Gomez-Sal
    Halogen Bonding (HaB) in E-I···X-M Systems: Influence of the Halogen Donor on the HaB Nature, CrystEngComm., 2020, 22, 870-877, DOI: 10.1039/c9ce01449g *Selected as Front Cover*
    Supramolecular & Polymorphism and 1st International Conference on Noncovalent Interactions.
  • M. Fernandez-Millan, M. Temprado, J. Cano, T. Cuenca, M. E. G. Mosquera
    Alkali-Metal Compounds with Bio-Based Ligands as Catalysts for Isoselective Lactide Polymerization: Influence of the Catalyst Aggregation on the Polymerization Control, Organometallics, 2020, 39, 2278-2286, DOI: 10.1021/acs.organomet.0c00237
  • S. Ghosh, D. Suparna, M. E. G. Mosquera
    Conducting Polymer-Based Nanohybrids for Fuel Cell Application. Polymers, 2020, 12, 2993, DOI: 10.3390/polym12122993.
  • V. Sessini, M. Palenzuela, J. Damián, M. E. G. Mosquera
    Bio-based Polyether from Limonene Oxide Catalytic ROP as Green Polymeric Plasticizer for PLA, Polymer, 2020, 210, 123003, DOI: 10.1016/j.polymer.2020.123003
  • T. L. Wootton, J. A. Porter, K. S. Grewal, P. G. Chirila, S. Forbes, S. Coles, P. N. Horton, A. Hamilton, C. J. Whiteoak
    Merging Cu-Catalysed C-H Functionalisation and Intramolecular Annulations: Computational and Experimental Studies on an Expedient Construction of Complex Fused Heterocycles, Org. Chem. Front., 2020, 7, 1235-1242, DOI: 10.1039/D0QO00283F
  • M. Chu, O. Planas, A. Company, X. Ribas, A. Hamilton, C. J. Whiteoak
    Unravelling the Mechanism of Cobalt-Catalysed Remote C-H Nitration of 8-Aminoquinolinamides and Expansion of Substrate Scope Towards 1-naphthylpicolinamide, Chem. Sci., 2020, 11, 534-542, DOI: 10.1039/C9SC05076K


  • F. G. García-Valle, V. Tabernero, T. Cuenca, J. Cano, M. E. G. Mosquera
    Intramolecular C–F Activation in Schiff-base Alkali Metal Complexes, Organometallics, 2019, 38, 894-904, DOI: 10.1021/acs.organomet.8b00868
  • M. Palenzuela, M. T. Muñoz, J. F. Vega, A. Gutiérrez-Fernández, T. Cuenca, M. E. G. Mosquera
    Heterobimetallic Aluminate Derivatives with Bulky Phenoxide Ligands: Catalyst for Selective Vinyl Polymerization, Dalton Trans., 2019, 48, 6435-6444, DOI:10.1039/C9DT00761J
  • Z. M. Heiden, M. E. G. Mosquera, H. B. Singh
    Inorganic Chemistry of the p-block Elements, Dalton Trans., 2019, 48, 6666-6668, DOI: 10.1039/c9dt90098e
  • F. G. García-Valle, M. T. Muñoz, T. Cuenca, S. Milione, J. Cano, M. E. G. Mosquera
    Fluorinated Alkali Metal Catalysts for the Ring-Opening Polymerization (ROP) of rac-lactide. Effect of the M···F Interactions in the Polymerization Control, J. Organomet. Chem., 2019, 898, 120854, DOI: 10.1016/j.jorganchem.2019.07.005


  • M. T. Muñoz, M. Palenzuela, T. Cuenca, M. E. G. Mosquera
    New Aluminium Aryloxide Compounds Very Active Catalysts for Glycidyl Methacrylate Selective ROP Polymerization, ChemCatChem., 2018, 10, 936-939, DOI: 10.1002/cctc.201701377
  • F. M. Garcia-Valle, T. Cuenca, V. Tabernero, M. E. G. Mosquera, J. Cano, S. Milione
    Biodegradable PHB from rac-β-Butyrolactone: Highly Controlled ROP Mediated by a Pentacoordinated Aluminum Complex, Organometallics, 2018, 37, 837-840, DOI: 10.1021/acs.organomet.7b00843
  • M. E. G. Mosquera, V. Tabernero, F. M. García-Valle, J. Cano, T. Cuenca
    Schiff-base-ate Derivatives with Main Group Metals: Generation of a Tripodal Aluminate Metalloligand, Dalton Trans., 2018, 47, 6499-6506, DOI: 10.1039/c8dt00835c
  • S. M. F. Vilela, A. A. Babaryk, R. Jaballi, F. Salles, M. E. G. Mosquera, Z. Elaoud, S. Van Cleuvenbergen, T. Verbiest, P. Horcajada
    A Nonlinear Optically Active Bismuth–Camphorate Coordination Polymer, Eur. J. Inorg. Chem., 2018, 2437-2443, DOI: 10.1002/ejic.201800197
  • I. Reviejo, V. Tabernero, M. E. G. Mosquera, J. Ramos, T. Cuenca, G. Jiménez
    Chiral Titanium(IV) Complexes Containing Polydentate Ligands Based on α Pinene. Catalytic Activity in Sulfoxidation with Hydrogen Peroxide. Organometallics, 2018, 37, 3437-3449, DOI: 10.1021/acs.organomet.8b00163
  • F. G. García-Valle, V. Tabernero, T. Cuenca, J. Cano, M. E. G. Mosquera
    Schiff-base-ate Derivatives with Main Group Metals: Generation of a Tripodal Aluminate Metalloligand, Dalton Trans., 2018, 47, 6499-6506, DOI: 10.1039/c8dt00835c
  • F. G. García-Valle, V. Tabernero, T. Cuenca, J. Cano, M. E. G. Mosquera
    Aluminates with Fluorinated Schiff Bases: Influence of the Alkali Metal–Fluorine Interactions in Structure Stabilization, Molecules, 2018, 23, 3108, DOI:10.3390/molecules23123108
  • D. Sanchez-Roa, T. G. Santiago, M. Fernandez-Millan, T. Cuenca, P. Palma, J. Campora, M. E. G. Mosquera
    Interaction of an Imidazolium-2-amidinate (NHC-CDI) Zwitterion with Zinc Dichloride in Dichloromethane: Role as Ligands and C–Cl Activation Promoters, Chem. Commun., 2018, 54, 12586-12589, DOI: 10.1039/c8cc07661h
  • A. Kenny, A. Pisarello, A. Bird, P. G. Chirila, A. Hamilton, C. J. Whiteoak
    A Challenging Redox Neutral Cp*Co(III)-Catalyzed Alkylation of Acetanilides with 3-Buten-2-one: Synthesis and Key Insights into the Mechanism through DFT Calculations, Beilstein J. Org. Chem., 2018, 14, 2366-2374, DOI: 10.3762/bjoc.14.212
  • P. G. Chirila, L. Skibinski, K. Miller, A. Hamilton, C. J. Whiteoak
    Towards a Sequential One‐Pot Preparation of 1,2,3‐Benzotriazin‐4 (3H)‐ones Employing a Key Cp*Co(III)‐catalyzed C−H Amidation Step, Adv. Synth. Catal., 2018, 360, 2324-2332, DOI: 10.1002/adsc.201800133
  • P. G. Chirila, J. Adams, A. Dirjal, A. Hamilton, C. J. Whiteoak
    Cp*Co(III)‐Catalyzed Coupling of Benzamides with α,β‐Unsaturated Carbonyl Compounds: Preparation of Aliphatic Ketones and Azepinones, Chem. Eur. J., 2018, 24, 3584-3589, DOI: 10.1002/chem.201705785
  • I. de la Cueva-Alique, S. Sierra, L. Munoz-Moreno, A. Perez-Redondo, A. M. Bajo, I. Marzo, L. Gude, T. Cuenca, E. Royo
    Biological Evaluation of Water Soluble Arene Ru(II) Enantiomers with Amino-oxime Ligands, J. Inorg. Biochem., 2018, 183, 32-42, DOI: 10.1016/j.jinorgbio.2018.02.018
  • O. Planas, P. G. Chirila, C. J. Whiteoak, X. Ribas
    Current Mechanistic Understanding of Cobalt-Catalyzed C–H Functionalization, Adv. Organomet. Chem., 2018, 69, 209-282, DOI: 10.1016/bs.adomc.2018.02.002


  • J. Restrepo, Z. Serroukh, J. Santiago-Morales, S. Aguado, P. Gómez-Sal, M. E. G. Mosquera, R. Rosal
    An Antibacterial Zn-MOF with Hydrazinebenzoate Linkers, Eur. J. Inorg. Chem., 2017, 574-580, DOI: 10.1002/ejic.201601185
  • M. C. Maestre, P. B. Gratal, M. E. G. Mosquera, T. Cuenca, G. Jiménez
    A Suitable Strategy to Prepare Different N-Substituted Niobium Complexes: Study of the Factors Controlling the Process, Eur. J. Inorg. Chem., 2017, 1060-1066, DOI: 10.1002/ejic.201601360
  • M. T. Muñoz, G. Barandika, B. Bazán, T. Cuenca, M. E. G. Mosquera
    Novel Aluminium-alkali Metal-ate Derivatives: Factors Driving the Final Nuclearity in the Crystal Form, Eur. J. Inorg. Chem., 2017, 1994-2001, DOI: 10.1002/ejic.201601428
  • M. E. G. Mosquera, P. Gomez-Sal, I. Egido, M. Lopez Lopez, C. Hortelano
    Comparison of Halogen Bonding Networks with Ru(II) Complexes and Analysis of the Influence of the XB Interaction on their Reactivity, Faraday Discuss., 2017, 203, 257-283, DOI:10.1039/c7fd00079k
  • A. Londaitsbehere, M. Herrera, A. Salgado, M. E. G. Mosquera, T. Cuenca, J. Cano
    A Non-dissociative Mechanism for the Inversion of the Configuration in Cyclopentadienyl Di(aryloxo) Titanium Complexes: An Entropy Discussion, Organometallics, 2017, 36, 3904–3911, DOI: 10.1021/acs.organomet.7b00511
  • P. G. Chirila, C. J. Whiteoak
    Recent Advances Using [Cp*Co(CO)I2] Catalysts as a Powerful Tool for C–H Functionalisation, Dalton Trans., 2017, 46, 9721-9739, DOI: 10.1039/C7DT01980G


  • M. E. G. Mosquera, P. Gomez-Sal, I. Diaz, L. M. Aguirre, A. Ienco, G. Manca, C. Mealli
    Intriguing I2 Reduction in the Iodide for Chloride Ligand Substitution at a Ru(II) Complex: Role of Mixed Trihalides in the Redox Mechanism, Inorg. Chem., 2016, 55, 283-291, DOI: 10.1021/acs.inorgchem.5b02307
  • I. de la Cueva-Alique, L. Munoz-Moreno, Y. Benabdelouahab, B. T. Elie, M. A. El Amrani, M. E. G. Mosquera, M. Contel, A. M. Bajo, T. Cuenca, E. Royo
    Novel Enantiopure Cyclopentadienyl Ti(IV) Oximato Compounds as Potential Anticancer Agents, J. Inorg. Biochem., 2016, 156, 22-34, DOI: 10.1016/j.jinorgbio.2015.12.002
  • M. Fernandez-Millan, L. K. Allen, R. Garcia-Rodriguez, A. D. Bond, M. E. G. Mosquera, D. S. Wright
    Formation and Trapping of a Unique ‘Unsupported’ Hydridic Sn(II)Stannate, Chem. Commun., 2016, 52, 5993-5996, DOI: 10.1039/C6CC01885H.
  • M. Fernandez-Millan, M. Temprado, J. Cano, T. Cuenca, M. E. G. Mosquera
    Synthesis of Novel Chiral Heterometallic Terpene Oximates: Unusual Generation of an Aluminium Enolate by a Cooperative Effect, Dalton Trans., 2016, 45, 10514-10518, DOI: 10.1039/C6DT02116F
  • M. Ventura, V. Tabernero, T. Cuenca, B. Royo, G. Jiménez
    Cyclopentadienyl–Silsesquioxane Titanium Catalysts: Factors Affecting Their Formation and Activity in Olefin Epoxidation with Aqueous Hydrogen Peroxide, Eur. J. Inorg. Chem., 2016, 17, 2843-2849, DOI: 10.1002/ejic.201501474
  • C. Gallegos, R. Camacho, M. Valiente, T. Cuenca, J. Cano
    Cyclopentadienyl-based Mg Complexes in the Intramolecular Hydroamination of Aminoalkenes: Mechanistic Evidence for Cationic Versus Neutral Magnesium Derivatives, Catal. Sci. Technol., 2016, 6, 5134-5143, DOI: 10.1039/C5CY01040C
  • C. J. Whiteoak, O. Planas, A. Company, X. Ribas
    A First Example of Co-Catalyzed Remote C-H Functionalization of 8-aminoquinolines Operating through a Single Electron Transfer Mechanism, Adv. Synth. Catal., 2016, 358, 1679-1688, DOI: 10.1002/adsc.201600161


  • F. M. García-Valle, R. Stivill, C. Gallegos, T. Cuenca,  M. E. G. Mosquera, V. Tabernero, J. Cano
    Metal and Ligand-Substituent Effects in the Immortal Polymerization of rac-Lactide with Li, Na, and K Phenoxo-imine Complexes, Organometallics, 2015, 34, 477-487, DOI: 10.1021/om501000b
  • A. W. Kleij, C. J. Whiteoak
    Diastereo- and Enantioselective Valorization of Cyclic Organic Carbonates, ChemCatChem., 2015, 7, 51-53, DOI: 10.1002/cctc.201402801
  • S. Pedrosa, F. Vidal, L. Myongwon Lee, I. Vargas-Baca,  P. Gómez-Sal,  M. E. G. Mosquera
    Imido-Pyridine Ti(IV) Compounds: Synthesis of  Unusual Imido-Amido Heterobimetallic Derivatives. Dalton Trans., 2015, 44, 11119-11128, DOI: 10.1039/C5DT01320H
  • C. Gallegos, V. Tabernero, M. E. G. Mosquera, T. Cuenca, J. Cano
    Comparative Study of Lactide Polymerization with Lithium, Sodium, Potassium, Magnesium, Calcium, and Zinc Azo-naphthoxide Complexes, Eur. J. Inorg. Chem., 2015, 5124-5132, DOI: 10.1002/ejic.201500818
  • V. Laserna, G. Fiorani, C. J. Whiteoak, E. Martin, E. Escudero-Adán, A. W. Kleij
    Carbon Dioxide as a Protecting Group: Highly Efficient and Selective Catalytic Access to Cyclic cis-Diol Scaffolds, Angew. Chem. Int. Ed., 2014, 53, 10416-10419, 10.1002/anie.201406645
  • F. Fernández-Palacio, J. Restrepo, S. Gálvez, P. Gómez-Sal, M. E. G. Mosquera
    Functionalized Aminocarboxylate Moieties as Linkers for Coordination Polymers: Influence of the Substituents in the Dimensionality of the Final Structure, CrystEngCommun., 2014, 43, 14377-14385, DOI: 10.1039/c3ce42615g
  • M. Mosquera, M. J. Andres-Prado, G. Rodriguez-Caravaca, P. Latasa,  M. E. G. Mosquera
    Evaluation of an Education and Training Intervention to Reduce Health Care Waste in a Tertiary Hospital in Spain, Am. J. Infect. Control, 2014, 42, 894-897 (VI Premio de la Cátedra UAM-ASISA), DOI: 10.1016/j.ajic.2014.04.013
  • M. T. Muñoz, T. Cuenca, M. E. G. Mosquera
    Heterometallic Aluminates: Alkali Metals Trapped by an Aluminium Aryloxide Claw, Dalton Trans., 2014, 16, 3376-3386, DOI: 10.1039/C4DT00952 (Special Issue on New Expeditions in Polar Organometallic Chemistry)
  • G. Jiménez, T. Cuenca, L. Postigo, M. E. G. Mosquera, M. C. Maestre
    Aminoarenethiolate Aluminum Complexes: Synthesis, Characterization, and Use in L-lactide Polymerization, Organometallics, 2013, 32, 2618-2624, DOI: 10.1021/om400111f
  • A. Coppola, P. Sánchez-Alonso, D. Sucunza, C. Burgos, R. Alajarín, J. Alvarez-Builla, M. E. G. Mosquera, J. J. Vaquero
    Aryl Cyanation via Isocyanide–Cyanide Rearrangement on Tosylmethyl Isocyanide Derivatives, Org. Lett., 2013, 15, 3388-3391, DOI: 10.1021/ol401433x
  • F. Vidal, M. A. Dávila, A. San Torcuato, P. Gómez-Sal, M. E. G. Mosquera
    Functionalized Imido-Bridged Titanium Dinuclear Complexes as New Building Blocks for Supramolecular Arrangements: Generation of a 1D Structure through a Mg-Cl•••I-C Halogen Bonding Interaction, Dalton Trans., 2013, 42, 7074-7084, DOI:10.1039/c3dt32943g
  • C. Gallegos, V. Tabernero, F. M. García-Valle,  M. E. G. Mosquera, T. Cuenca, J. Cano
    Synthesis and Structure of Homo- and Heterometallic Lithium-magnesium Complexes and their Reactivity in the ROP of rac-lactide, Organometallics, 2013, 32, 6624-6627, DOI: 10.1021/om400940f
  • A. Londaitsbehere, J. Cano, T. Cuenca, M. E. G. González, S. Milione, A. Grassi
    1,3-Double Siloxo-Bridged Zirconium Metallocene for Propene and 1-Hexene Oligomerization Generation of a Dinuclear Aluminoxane, Organometallics, 2012, 31, 2108-2111, DOI: 10.1021/om2011535
  • G. Martinez, M. E. G. Mosquera, T. Cuenca
    Effect of the Nitrogen Substituent on the Reactions of Alane towards Imino and Aminophenols: Generation of a Dinuclear Aluminoxane, Eur. J. Inorg. Chem., 2012, 3611-3617, DOI: 10.1002/ejic.201200255
  • G. Chahboun, J. A. Brito, B. Royo, M. A. El Amrani, E. Gomez-Bengoa, M. E. G. Mosquera, T. Cuenca, E. Royo
    Olefin Epoxidation Catalyzed by Cis-dioxidomolybdenum(VI) Complexes Containing Chiral Alkoxo-imino Ligands Derived from (+)-α-pinene, Eur. J. Inorg. Chem., 2012, 2940-2949, DOI: 10.1002/ejic.201200144
  • M. Ventura, M. E. G. Mosquera, T. Cuenca, B. Royo, G. Jimenez
    Cyclopentadienyl-Silsesquioxane Titanium Complexes: Highly Active Catalysts for Epoxidation of Alkenes with Aqueous Hydrogen Peroxide, Inorg. Chem., 2012, 42, 6345-6349, DOI: 10.1021/ic300583g
  • M. Ventura, C. Ramírez de Arellano, M. E. G. Mosquera, G. Jimenez, T. Cuenca
    Synthesis and Structural Characterization of Novel Tetranuclear Organotitanoxane Derivatives, Dalton Trans., 2011, 5728-5733, DOI: 10.1039/c0dt01393e
  • C. Paniagua, M. E.G. Mosquera, G. Jimenez, T. Cuenca
    Reactions of [Ti(η5-C5Me4SiMe2Cl)Cl3] with Diamines, a Suitable Approach to Prepare Mono- and Dinuclear Cyclopentadienyl-silyl-amido Titanium Complexes with Constrained and Unstrained Structures, Organometallics, 2011, 30, 2993-3000, DOI: 10.1021/om200101k
  • G. Alesso, V. Tabernero, M. E. G. Mosquera, T. Cuenca
    Studies on the Active Species in Olefin Polymerisation Generated from Phenoxo-amido Titanium “Chiral-at-metal” Compounds, J. Organomet. Chem., 2011, 696, 2330-2337, DOI: 10.1016/j.jorganchem.2011.02.011
  • M. T. Muñoz, C. Urbaneja, M. Temprado, M. E. G. Mosquera, T. Cuenca
    Lewis Acid Fragmentation of a Lithium Aryloxide Cage: Generation of New Heterometallic Aluminium-Lithium Species. Chem. Commun., 2011, 47, 11757-11759, DOI:10.1039/c1cc14577k