Partitioning a sequence into sets of unique pairs

I'm in need a of function which can split a sequence into pairs, and then combine them such that all elements in a combination is unique. I have tried a number of approaches using python's itertools, but have not found a solution.

To illustrate i would like a function which would take this sequence:
[1, 2, 3, 4]

and split it into the following 3 combinations:

[[1, 2], [3, 4]]
 [[1, 3], [2, 4]]
 [[1, 4], [2, 3]]
 

it should also work for longer sequences, but does not have to handle sequences of odd length. eg.

[1,2,3,4,5,6]
 

splits into the following 15 combinations:

[[1, 2], [3, 4], [5, 6]]
 [[1, 2], [3, 5], [4, 6]]
 [[1, 2], [3, 6], [4, 5]]
 [[1, 3], [2, 4], [5, 6]]
 [[1, 3], [2, 5], [4, 6]]
 [[1, 3], [2, 6], [4, 5]]
 [[1, 4], [2, 3], [5, 6]]
 [[1, 4], [2, 5], [3, 6]]
 [[1, 4], [2, 6], [3, 5]]
 [[1, 5], [2, 3], [4, 6]]
 [[1, 5], [2, 4], [3, 6]]
 [[1, 5], [2, 6], [3, 4]]
 [[1, 6], [2, 3], [4, 5]]
 [[1, 6], [2, 4], [3, 5]]
 [[1, 6], [2, 5], [3, 4]]
 

... and so on.

The CAS called Maple has this function implemented under the name setpartition.

Edit: fixed a critical late night typing error pointed out by wks, and clarified the outputs.

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