Exxon Corp., the nation's largest oil company said today it would pay $1.165 billion for Reliance Electric Co., a manufacturing company Exxon wants to produce a device that cuts power consumption in electric motors.

Exxon said that it the Reliance board of directors agrees, Exxon will pay $72 a share for Reliance common stock and $201.60 a share for convertible preferred stock. Before Exxon announced last Friday that it was interested in taking over Reliance, the electrical company's common stock was trading at $36.50 a share on the New York Stock Exchange.

The merger negotiations have been friendly, Exxon said. Reliance Chairman B. Charles Ames has agreed to take Exxon's proposal to the companyhs directors.

Exxon said last Friday it wanted to acquire Reliance and use the company to develop and market variable-voltage and variable-frequency power technology, which Exxon hopes will control the speed of medium-sized electrical motors and increase their efficiency.

Reliance said that as of Jan. 31 it had 15,568,716 common shares and about 250,000 convertible preferred shares outstanding, giving the Exxon offer a value of $1.165 billion - one of the biggest in corporate history.tEarlier this week Reliance said difficult legal questions would arise if Exxon made an offer for the company. Federal antitrust regulators are expected to take a hard look at Exxon's offer.

Reliance, based in Cleveland, had sales of $966 million last year and profits of $64.6 million.