Ending speculation as to whether it was acting alone in its purchase of Penton Media, Wasserstein & Co. said today that MidOcean Partners will own 50 percent of the business upon the completion of its merger with Prism Business Media.

Wasserstein vice chairman Anup Bagaria and MidOcean Partners managing director Tyler Zachem will serve as co-chairmen of the Prism/Penton entity. Financial terms of the transaction between MidOcean and Penton were not disclosed. UBS advised Wasserstein & Co. on its partnership with MidOcean.

Prism, owned by an investment fund sponsored by Wasserstein and its investment partners Highfields Capital Management and Lexington Partners, announced November 2 it had purchased Penton for $194.2 million, plus assumption and payment of debt, putting the total value of the deal at $530 million.

Though Wasserstein did not initially announce its partnership with MidOcean, one source had told Folio: Alert that Wasserstein’s resources were running low, having put $150 million into Prism and more into Hanley Wood, and thus would need to find a partner to buy Penton.

Prism’s acquisition of Penton is expected to close in the first half of 2007. Wasserstein has yet to announce who will serve as CEO of the new company – Penton is currently helmed by David Nussbaum and Prism is led by John French.

Analysts say it’s a tough call as both Nussbaum and French are qualified to do the job. Nussbaum runs a $200 million company and is viewed by some to be the more seasoned professional, but French’s $250 million company is doing very well financially due to a string of successful acquisitions and strong organic growth.