extend variable to double array

I need fix of code below.

I have a variable called:
var node = new string[1][];
node[0] = "node1";

Then I need this node[0] extended to object like this:
node[0] { new object[] {
"client", new HttpClient(),
"url", "http://test.com",
"rpc_user", "testuser",
"rpc_pass", "testpass"
}


so output will be

node["node1"]["client"] = HttpClient;
node["node1"]["url"] = "http://test.com"
node["node1"]["rpc_user"] = "testuser"
node["node1"]["rpc_pass"] = testpass"