The I2C module can operate while in Sleep mode.
In Slave mode, the module can transmit and receive data as long as the system clock source operates in Sleep. If the generic I2C Interrupt Enable (I2CxIE) bit is set and the slave receives or transmits a complete byte, I2CxIF is set and the device wakes up from Sleep.
In Master mode, both the system clock and the selected I2CxCLK source must be able to operate in Sleep. If the I2CxIE bit is set and the I2CxIF bit becomes set, the device wakes from Sleep.