Reede by Veronica Scott

Lt. Fallyn Damara was sent by the Sectors to investigate a strange transmission from an isolated planet and determine whether the residents of a vanished colony had been transported there by alien enemies. Fallyn’s ship crashes and she’s taken prisoner by the Khagrish scientists, to await her fate in the slate of horrifying experiments being conducted.
Reede, the second ranking enforcer in the Badari Warrior pack, volunteers to be recaptured by the Khagrish in an effort to locate and rescue Fallyn inside the deadly lab complex.
While a prisoner Reede discovers Fallyn is the woman destined to become his fated mate but the moment is bittersweet because Fallyn will be leaving their world at the first opportunity, to report back to the Sectors. He refuses to complete the mate bond, believing to do so will lead to nothing but lifelong misery for them both, separated by lightyears and interstellar politics.
For her part, Fallyn wants to shake up the rule-bound enforcer and persuade him to take a chance on love.
But first they have to escape the Khagrish.