The merging gap is a critical decision-making factor for the lane-changing maneuver and can significantly impact the course of the lane-changing maneuver. Particularly, the gap size affects the interaction between the lane-changing car and its follower in the target lane, and an insufficient gap can result in significant disruption in the target lane. To address this challenge, this study proposes a vehicle platooning control to extend the merging gap under a connected environment. We focus on reducing the magnitude of the backward moving shockwave in the target lane (due to the addition of the lane-changing vehicle) by adjusting the time headways of the vehicles in front of the merging gap and generating an additional gap for the lane-changing maneuver. This study proposes an optimization framework to generate a set of new time headways and introduces a robust control framework to achieve these new time headways. The proposed controller utilizes a combination of Adaptive Cruise Control (ACC) and Model Predictive Control (MPC). The simulation results indicate that, by leveraging the car-following capability of ACC and connectivity, the proposed algorithm is capable of creating a naturalistic forward-moving shockwave and extending the merging gap.