Bateman never worked for Mercury Records. He was an independent producer, working almost exclusively in New York in 1965 and 1966 (still producing a couple records in Detroit). He had a couple of his productions leased to Mercury affiliates during those years. He had some of his NY productions on many, many labels (20th Century Fox, ABC, Philips, Smash, Capitol, Atlantic, MGM, Riverside, Buddah, etc.).
He left Motown in spring 1962, when Wilbur Golden started Correc-Tone Records, and enticed some Motowners to "jump ship" to his new label. Mickey Stevenson, lamont Dozier, The Holland Brothers, Popcorn Wylie, Sonny Sanders and the rest of The Satintones were ready to move. But Berry Gordy persuaded HDH and Stevenson to stay by buying them new cars and offering them high regular salaries. His offers to Bateman, Sanders and Wylie were too low to keep them, so they jumped (not knowing that the others were staying). Already within 6 months, Golden was running out of cash, having put out a lot to have Bateman build him a new recording studio, and also paying for recording and pressing of Correc-Tone's and SonBert's first few releases. So, Golden sent Bateman to New York to try to lease some of their Correc-Tone recordings and sell publishing to some of their songs. Bateman spent increasingly more time in New York than Detroit, while selling off and leasing Correc-Tone product in the remainder of 1962 and throughout 1963, also working on his own independent productions there, as Golden didn't have the money to pay him his salary. Bateman ended up staying permanently in New York, but returning to Detroit for specific productions (Luther Ingram on HIB, Mary Wells 20th Century Fox recordings, etc. By early 1964, Bateman had split from Golden and Correc-Tone, and become an independent NY producer.