your JSON string seems not correct. try to use this:

{"list": [
    "p1": {
      "a": 6,
      "b": 7
    },
    "p2": {
      "a": 1,
      "b": 1
    }]
}

your JSON string seems not correct. try to use this:

{"list": [
    "p1": {
      "a": 6,
      "b": 7
    },
    "p2": {
      "a": 1,
      "b": 1
    }]
}

I've added an opening brackets for the list in order to mark it as an object and changed the array opening brackets to square brackets.