Device for the motorised opening and the closing in gusset of a turn-tilt window closing an aperture plane and comprising an opening member and a casing, said device comprises: a. a rigid chain actuator, installed in the frame of the casing and able to produce a thrust and a traction along a direction perpendicular to the aperture plane; b. a coupling assembly that can be disconnected comprising a connection pin fixed to the end of the chain of the chain actuator and a coupling member integral with the opening member, comprising a sliding hardware that comprises a grasping fork in the frame of the opening member, with the opening of said grasping fork being oriented in order to allow for the introduction of the pin into said fork by a translation along a direction substantially parallel to the largest dimension of the profile of the frame of the casing; c. a mechanism for displacing the sliding hardware, parallel to the aperture plane, and for carrying out the connection or the disconnection of the opening member with the rigid chain actuator; d means for locking the opening member in the closed position comprising a bolt and a striker with one of the bolt or of the striker being linked to the sliding hardware and being displaced with the latter; e. a manoeuvring pin fixed to the sliding hardware; f. a manoeuvring fork (512, 612, 613, 712) integral with the casing and acting on the manoeuvring pin when the window is in the closed position and of which the opening is perpendicular to the direction of displacement of the opening member during the gusset opening-closing; g. means comprising a locking motor (302, 602), installed in the frame of the casing, to displace in translation the sliding hardware over a stroke of length l, said stroke of length l of the sliding hardware starting from the closed and locked position of the window, connecting the coupling assembly, while moving the bolt away from the striker, in such a way as to unlock the opening member and allow for the opening of the window; characterised in that the connection pin is formed from a ferromagnetic material, with the grasping fork being formed from a non-magnetic material and comprising a permanent magnet for maintaining the connection pin in the grasping fork. a. a rigid chain actuator, installed in the frame of the casing and able to produce a thrust and a traction along a direction perpendicular to the aperture plane; b. a coupling assembly that can be disconnected comprising a connection pin fixed to the end of the chain of the chain actuator and a coupling member integral with the opening member, comprising a sliding hardware that comprises a grasping fork in the frame of the opening member, with the opening of said grasping fork being oriented in order to allow for the introduction of the pin into said fork by a translation along a direction substantially parallel to the largest dimension of the profile of the frame of the casing; c. a mechanism for displacing the sliding hardware, parallel to the aperture plane, and for carrying out the connection or the disconnection of the opening member with the rigid chain actuator; d means for locking the opening member in the closed position comprising a bolt and a striker with one of the bolt or of the striker being linked to the sliding hardware and being displaced with the latter; e. a manoeuvring pin fixed to the sliding hardware; f. a manoeuvring fork (512, 612, 613, 712) integral with the casing and acting on the manoeuvring pin when the window is in the closed position and of which the opening is perpendicular to the direction of displacement of the opening member during the gusset opening-closing; g. means comprising a locking motor (302, 602), installed in the frame of the casing, to displace in translation the sliding hardware over a stroke of length l, said stroke of length l of the sliding hardware starting from the closed and locked position of the window, connecting the coupling assembly, while moving the bolt away from the striker, in such a way as to unlock the opening member and allow for the opening of the window;