Web.Contents failed to get contents from 'https://ausreman.tidywork.com/api/materials' (400)

I have tried a number of scenarios for posting data, but I have come up with nothing.  I am trying to write a power query that posts data to a REST API (https://ausreman.tidywork.com/api/materials), it posts data for materials.  The current query I have is:

= Json.Document(Web.Contents("https://ausreman.tidywork.com/api/materials",[Headers=
        [#"Authorization"="Basic ZZZZZZZZZZZZZZZZZ",#"Content-Type"="application/json"],
       Content=Json.FromValue({[projectId="65b6d1fe-ec2e-47c3-9c92-2aad8fdd1d26",userId="67220adb-d5cb-4667-a3ce-ebe3d6248334",materialDateUtc="2015-09-14T07:11:00",materialDate="2015-09-14T17:11:00",materialId="00000000-0000-0000-0000-000000000000",materialLocationId="1aeb9552-a3e9-4804-a7b2-641b290dac8d",materialItemCode="1H3338",materialItemId="f9be8264-81f0-4ae2-a12b-569b3e05d034",costCurrencyId="17709522-6b2e-4b01-9cdf-bb7eb0a43c52",chargeCurrencyId="17709522-6b2e-4b01-9cdf-bb7eb0a43c52",taskId="b2ffc2cf-326a-fc91-eb40-c4ddb4147a35",state="Approved",usageQuantity=1,quantity=1,cost=0.21,charge=0.25]})]), 1252)

The only thoughts I had was that it had something along the lines of the size of the data being post.   Please help me remove this frustration.