Pre-print version of the article forthcoming in Organization Science BEING A CATALYST OF INNOVATION: THE ROLE OF KNOWLEDGE DIVERSITY AND NETWORK CLOSURE Marco Tortoriello IESE Business School 28023 Madrid, Spain mtortoriello@iese.edu Bill McEvily Rotman School of Management University of Toronto Toronto, Ontario M5S 3E6, Canada bill.mcevily@rotman.utoronto.ca David Krackhardt Carnegie Mellon University Pittsburgh PA, 15213, US krack@cmu.edu (forthcoming in Organization Science) Keywords: Innovation, Social Networks, Catalysts Acknowledgments: This research is supported by the Ewing Marion Kauffman Foundation, the Fondazione IRI Research Fellowship, IESE Business School, the Spanish Ministry of Science and Innovation (ECO2011- 23220 and ECO2011-13361-E), and the Singapore National Research Foundation under its International Research Centre @ Singapore Funding Initiative and administered by the IDM Programme Office. The generous support of the Center for Organizational Learning, Innovation and Knowledge at the Tepper School of Business - Carnegie Mellon University is also gratefully acknowledged. We would like to thank senior editor Steve Borgatti for his guidance, Linda Argote, Fabrizio Ferraro, David Hounshell, Pablo Ruiz- Verdú, seminar participants at Dartmouth College, Grenoble Ecole de Management, Rotman School of Management, Universidad Carlos III de Madrid, University of Michigan, Washington University in St. Luis, for their comments and insightful suggestions. Remaining mistakes are our own.