LONDON (Reuters) - The Jacobs group said it is to sell a 16 percent stake in Adecco (>> Adecco SA), the world's largest staffing agency, as members of the Jacobs family seek to diversify by cutting their holdings in the company they helped found.

Swiss investment group Jacobs Holding AG and members of the family, who also have a majority stake in Barry Callebaut (>> Barry Callebaut AG), will reduce their stake in Adecco to 2.5 percent in an accelerated bookbuilding.

A source familiar with the matter said the offer was being priced at between 71 and 73 swiss francs ($81.2 - $83.5 (50.25 pounds)) per share, valuing the stake at up to 2.2 billion swiss francs $2.52 billion (1.51 billion pounds).

Klaus Jacobs, who helped establish Adecco, also founded Barry Callebaut. The firm is now the world's biggest cocoa manufacturer, making chocolate for Nestle (>> Nestle SA) and Mondelez (>> Mondelez International Inc), among others.

Jacobs Holding said Barry Callebaut would maintain its position at the heart of its portfolio.

The bookbuilding for Adecco, which will be run by Goldman Sachs (>> Goldman Sachs Group Inc), will see Jacobs Holding AG and some Jacobs family members sell 30.2 million shares, leaving them with 4.7 million shares in the company.

Adecco beat fourth-quarter profit forecasts and posted an increase in revenue for the first time in seven quarters earlier on Wednesday, helping shares rise 4.5 percent to close at 78.60 francs. A price of 71 francs would represent a discount of 9.7 percent.

"We seek to build a more diversified investment portfolio around Barry Callebaut with our professional holding company and we will decide on new participations and investments over time," said Andreas Jacobs, Chairman of Jacobs Holding AG.

Adecco was not immediately available for comment.

(Additional reporting by Alice Baghdijan in Zurich, editing by Louise Heavens)

By Freya Berry