Pandas to parquet file

I am trying to save a pandas object to parquet with the following code:

LABL = datetime.now().strftime("%Y%m%d_%H%M%S")
df.to_parquet("/data/TargetData_Raw_{}.parquet".format(LABL))

this gives me the error:

ArrowTypeError: ("Expected bytes, got a 'float' object", 'Conversion failed for column Pre-Rumour_Date with type object')

The pandas dtypes are as follow:

0
Announced_Date                  object
Completed_Date                  object
Pre-Rumour_Date                 object
                                object
Lapsed_Date                     object
Target_Company                  object
Bidder_Company                  object
Seller_Company                  object
Deal_Value_USD(_m)              object
Exit_Type                       object
Buy_Type                        object
Sell_Stake_(%)                  object
Buy_Stake_(%)                   object
Months_Held                     object
Private_Equity_House            object
ADATE                   datetime64[ns]
dtype: object