Jira post request 400 bad request

public void createIssue()
       {

           string data = "{'fields': {'project':{'key': 'RSSPSI'},'summary': 'Test','description': 'TESTING','issuetype': {'name': 'Staging Installations'},'customfield_10807': '2018 - 09 - 19T10: 00:00.000 + 0000','customfield_15924': [{'value':'TEST 10'}],'customfield_11201': {'value':'RS2SP'},'customfield_16000': 'API TEST','components': [{'name':'System Engineer'}]}}";
           using (var client = new HttpClient())
           {
               client.BaseAddress = new Uri("https://LINKTOJIRA/rest/api/2/");

               byte[] cred = UTF8Encoding.UTF8.GetBytes("username":" + "password");

               client.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Basic", Convert.ToBase64String(cred));
               client.DefaultRequestHeaders.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));

               var content = new StringContent(data, Encoding.UTF8, "application/json");

               System.Net.Http.HttpResponseMessage response = client.PostAsync("issue", content).Result;
               Console.WriteLine("Create Issue Response : \n" + response);
           }




       }