Goldman Sachs Group Inc. and Citigroup Inc. are marketing $876 million of bonds backed by commercial mortgages, according to a person familiar with the offering. The securities, tied mostly to malls, shopping centers and office buildings, are supported by 43 loans on 108 U.S. properties, said the person, who declined to be identified because terms aren’t public. The bonds are slated to be sold next week, the person said.