While these two things are related in a sense, they are rather different things. It is possible for the two to affect one another, but they are not the same thing.
Organizational culture can be defined as the set of attitudes and behaviors that are typical to people in a given organization. It can include things like the ways in which people speak to one another or the kinds of clothes that they wear. It includes things like the attitudes that they have towards authority or towards hierarchy. The culture of an organization affects the ways in which people work in that organization and it affects the ways in which they interact with one another.
Organizational leadership is the process of steering an organization. Leaders of organizations try to influence the overall direction of the organization. They try to set goals for that organization and to inspire and persuade people to agree with those goals and to pursue them.
Organizational culture and organizational leadership can affect one another. The effects can go both ways. Leaders can potentially change the organizational culture. However, the organizational culture, particularly in a large organization, can be very hard to change and can end up changing the leaders and making them give into the preexisting organizational culture.