您可以将数据保存到xlsx。之后，您可以使用以下代码将xlsx文件转换为xls：

library(RDCOMClient)

xlApp <- COMCreate("Excel.Application")
xlApp[["DisplayAlerts"]] <- FALSE
xlApp[["Visible"]] <- TRUE

path_To_XLSX_File <- "D://excel_File_XLSX.xlsx"
path_To_XLS_File <- "D://excel_File_XLS.xlsx"

xlWbk <- xlApp$Workbooks()$Open(path_To_XLSX_File)

# https://learn.microsoft.com/en-us/office/vba/api/excel.xlfileformat
xlWbk$SaveAs(path_To_XLS_File, 56)