Martin Sorrell's S4 Capital buys programmatic ad firm MightyHive

LONDON (Reuters) - Martin Sorrell's S4 Capital has agreed to buy San Francisco-based programmatic ad firm MightyHive for an enterprise value of $150 million, funded by the issue of new shares worth 74 million pounds ($94 million).

Sorrell said the deal marked an important second strategic step for his new company. "The peanut has now morphed into a coconut, and is growing and ripening," he said on Tuesday.

He launched S4 Capital earlier this year shortly after he left WPP, the world's biggest advertising group, over a complaint of personal misconduct, which he denied.

Sorrell beat his old firm in July to buy Dutch digital agency MediaMonks, agreeing to pay 300 million euros for a digital agency that creates content and campaigns for clients including Adidas, Amazon, Google, Netflix and Hyundai.

Adding MightyHive's programmatic capabilities to MediaMonk's creative offer would enable S4 to offer clients fully integrated purely digital marketing, he said.

The new capital raising is led by Stanhope Capital, which will be a long-term strategic partner, S4 said. Daniel Pinto, Stanhope Capital's founder and chief executive, will join the board.

MightyHive uses algorithms to buy and sell advertising space online in real time.

($1 = 0.7850 pounds)

(Reporting by Paul Sandle; editing by Kate Holton and Sarah Young)