Introduction

The findings of the latest Eurobarometer survey show the majority of respondents think digitalization has a positive impact on the economy (75 percent), quality of life (67 percent), and society (64 percent). Indeed, people's daily lives and businesses have been highly transformed by digital technologies in the last years. Digitalization allowed to connect more than 8 billion devices worldwide, modified information value and management, and started to change the nature of organizations, their boundaries, work processes, and relationships.

Digital transformation refers to the adoption of a portfolio of technologies that, at varying degrees, have been employed by the majority of firms: Internet (IoT), digital platforms, social media, Artificial Intelligence (AI), Machine Learning (ML), and Big Data. These tools and instruments are "rapidly becoming as infrastructural as electricity". At macro levels, the shift toward different technologies is setting the agenda for new mechanisms of competition, industry structures, work systems, and relations to emerge. At the micro level, the digitalization has impacted on business dynamics, processes, routines, and skills.

Across different sectors and regardless of organization size, companies are converting their workplaces into digital workplaces. As observed by Haddud and McAllen, many jobs now involve extensive use of technology, and require the ability to exploit it at a fast pace. Yet, digitalization is being perceived both as a global job destroyer and creator, driving a profound transformation of job requirements. In result, leaders need to invest in upskilling employees, in an effort to support and motivate them in the face of steep learning curves and highly cognitively demanding challenges. Moreover, increased connectivity and information sharing is contributing to breaking hierarchies, functions and organizational boundaries, ultimately leading to the morphing of task-based into more project-based activities, wherein employees are required to directly participate in the creation of new added value. As such, the leadership role has become vital to capture the real value of digitalization, notably by managing and retaining talent via better reaching for, connecting and engaging with employees. However, leaders need to be held accountable for addressing new ethical concerns arising from the dark side of digital transformation. For instance, regarding the exploitation of digitalization processes to inflict information overload onto employees, or to further blur the lines between one's work and personal life.

In the last few decades, leadership scholars have been trying to monitor the effects of digitalization processes. Part of the academic debate has been focused on the role of leaders' ability to integrate the digital transformation into their companies and, at the same time, inspire employees to embrace the change, which is often perceived as a threat to the current status quo. To bring clarity to this debate, the construct of e-leader has been introduced to describe a new profile of leaders who constantly interact with technology. Accordingly, e-leadership is defined as a "social influence process mediated by Advanced Information Technology (AIT) to produce a change in attitudes, feelings, thinking, behavior, and/or performance with individuals, groups, and/or organizations".

Despite the increasing interest in discussing the relationship between digital technology and leadership, contributions have accumulated in a fragmented fashion across various disciplines. This fragmentation has made scholars struggle "to detect larger patterns of change resulting from the digital transformation". It also suggests that scholars have relied on multiple theoretical models to explain the phenomenon. Indeed, if, on one hand, it is clear that organizations are changing due to technological improvements, on the other hand, the way in which the transformation is occurring remains under debate. Furthermore, due to the fast-changing development and implementation of digital technology, there is a need to continuously update and consider the latest contributions to the topic.

This article addresses the aforementioned issues by offering a systematization of the literature on digitalization and leadership that has been accumulating across different disciplines, while adopting an interdisciplinary approach and providing a systematization of articles from different fields that analyze digitalization and leadership. Specifically, the present article reviews the literature on how the advent of digital technologies has changed leaders and leadership roles. Moreover, it structures and summarizes the literature, considering both theoretical frameworks and empirical findings, and fostering the understanding of both the content of the debate and its practical underpinnings. Lastly, reflecting on the findings of this review, we offer suggestions for future directions of research.

The present review draws on the following boundary conditions. First, we relied on a broad definition of leadership, in which the leader is understood as a person who guides a group of people, an organization, or empowers their transformational processes. Second, we excluded studies referring to market or industry leaders, in which the leader is represented by an organization. Third, we considered studies that clearly referred to a digital or technological transformation. Fourth, we did not include studies in which there was not a clear link between information technology and leadership (e.g., city leaders protecting the physical and digital infrastructures of urban economies regarding climate change). Therefore, our review was guided by the following research questions: (i) What are the main theoretical frameworks guiding the academic discussion on digital transformation and leadership? (ii) What are the main categories emerging from the contributions that address the relationship between digital transformation and leadership? And (iii) Which are the main future directions of research that scholars should consider?

This paper is structured as follows: First, it describes the methodology used; Second, it proposes a classification of findings based on theoretical frameworks and content. Finally, it describes implications of our findings for both research and practice, and proposes directions for future research.