I agree with the comments above where a successful team leader should have good interpersonal skills. It is essential for the leader to additionally have knowledge of the market place, costs of competitors and understand the customer you are trying to sell to. Along with this I believe emotional intelligence is another added skill that is needed. Emotional intelligence is the capability of individuals who recognize their own, and other people’s emotions, to discern between different feelings and label them appropriately, to use emotional information to guide thinking and behavior, and to manage and/or adjust emotions to adapt environments or achieve one’s goal. This aspect is quite beneficial in negotiating because having this understanding creates a better relationship between the leader and customer.

Coleman, Andrew (2008). A Dictionary of Psychology (3 ed.). Oxford University Press. ISBN 9780199534067.