Magento – Order not placed in magento2

Please try the below code.

"paymentMethod": {
    "method": "custom_pay",
    "additional_information": {
        "cc_cid": "000",
        "cc_type": "VI",
        "cc_exp_year": "2017",
        "cc_exp_month": "2",
        "cc_number": "xxxxxxxxxxxxxxxx"
    }
}

I hope it will be help you.

Here how Braintree integration looks like (https://developers.braintreepayments.com/start/overview)

So you need do the following

1) Get client token from Magento server. I didn't find rest endpoint for it so I've created a custom extension for this purpose (https://github.com/troublediehard/mma-customapi)

2) Then use sdk and token to get nonce from you card

3) And send your request with nonce data like this

{
  paymentMethod: {
    method: 'braintree',
    additional_data: { 
      payment_method_nonce: nonce, 
    }
  }
}