One of Arlington County's major moderate-cost garden apartment complexes, the 655-unit Arlington Village, was sold yesterday by a Boston-based firm to five local real estate developers for $9.7 million.

The 41-year-old complex, owned since 1952 by New England Mutual Life Insurance Co., was purchased by a group headed by Leland Phillips, president of Frank S. Phillips Co. of Washington.

Although the county's deputy planning director, Thomas C. Parker, yesterday called the complex "an obvious choice" for conversion to condominiums, Phillips ruled out any such immediate proposal.

"We know condominium conversion is on everybody's mind, but exactly what we'll do with it we don't know," Phillips said. "It's a good investment and a handsome property, but we're not going to rush in and do anything tomorrow. We're studying all the options."

Phillips said there would be no immediate increases in rents, which average $250 for a two-bedroom unit.

County housing officials said the sale comes at a time when Arlington's apartment vacancy rate is less than 1 percent, one of the lowest in the metropolitan area. Another large county apartment complex. Fairlington Villages, underwent condominium conversion starting in 1972.

The 40-acre, red brick Arlington Village property is on South Barton Street near Columbia Pike, about three miles from downtown Washington.

Phillips' partners in the purchase are Perston Caruthers, Paul Nassetta, Wallace Holladay and Terry Eakin.