I2C and powering


I would like to put 2 arduino nano in communication with I2c protocol and feed them via Lypo. Regarding the power supply, do I have to connect the Lypo to the Vin of the Master and the 5v of the Master to the Vin of the Slave or is each Arduino connected to the Lypo independently?
Thanks in advance

What is Lypo?

Is it possible that you mean LiPo (Lithium Polymere accu) instead of "Lypo"?

Usually it's not a good idea to feed the Arduino directly from an accu because most Arduinos have a linear voltage regulator on-board which wastes a lot of energy compared to a DC/DC converter that does the same conversion.

If the two Nanos are so close together that you can feed both from the same source, why do you need two of them?

Please describe your project in more detail and provide links to the used hardware (you can omit links to hardware available on arduino.cc).