Investors bet that the deal would repeat the success of Mr. Weill's other mergers, notably Salomon Brothers and Citicorp, while bolstering Citigroup's presence in Asia, where Mr. Weill is staking a big part of his company's future. ''it is the perfect Sandy Weill transaction,'' said Joan Solotar, an analyst at Credit Suisse First Boston who follows Citigroup. ''it is a business he knows, there are r