Competition in research has led to the emergence of new regional spaces and interorganizational arrangements, designed to improve their participants’ visibility, at the crossroads of regional systems and global exchanges. This article investigates the determinants of the formation of interregional scientific alliances through the in-depth case study of a federation of research laboratories in green chemistry in western France. Working from bibliometric and qualitative data and using a network analysis approach to evidence interurban network failures in this scientific field, we examine the federation’s geographical scope. We highlight the decisive role of (1) the spatial organization of the field (structure effect), (2) interpersonal ties between consortium members (network effect) and (3) national scientific guidelines and incentives (policy effect). We propose a novel mixed-method approach to understand interregional alliances and defend its potential to uncover the importance of interregional institutional arrangements in prompting interurban knowledge exchanges.