XML-RPC request WordPress

I have no problems to get the value of name in terms (name of my blog post category) out of the xmlrpc server response object …

Server response:

responseArray: ( 
    { guid = "http://www.domain.com/wp/?p=12";
      "post_id" = "123";
      terms = (
          { name = "Uncategorized"; }
      );
    }

)

… with the following lines of Objective-C code:

NSMutableArray *responseArray = [[NSMutableArray alloc] init];
responseArray = [nodeSaveResponse object];

for(i = 0; i < responseArray.count; i++) {

    NSString *postLink = [[responseArray objectAtIndex: i] valueForKey: @"guid"];
    NSString *postId = [[responseArray objectAtIndex: i] valueForKey: @"post_id"];

    NSMutableArray *catArray = [[NSMutableArray alloc] init];
    catArray = [[responseArray objectAtIndex: i] valueForKey: @"terms"]];
    NSArray *cat = [catArray valueForKey: @"name"];
    NSString *myCatString = [cat objectAtIndex: 0];
}

But to send a new blog post fails because the following code to pack the category string is somehow wrong:

NSString *myCatString = @"MyCategory";
NSMutableDictionary *name = [[NSMutableDictionary dictionaryWithObjectsAndKeys: myCatString, @"name", nil];
NSMutableArray *catArray = [[NSMutableArray arrayWithObject: name];

NSMutableDictionary *values = [[NSMutableDictionary alloc] init];
[values setObject: title forKey: @"post_title"]; 
// and so on with other values - until here everything works well
[values setObject: catArray forKey: @"terms"]; // if this line is called, the request fails

NSArray *params = [NSArray arrayWithObjects: @"1", user, pass, values, nil];
[myRequest setMethod: @"wp.newPost" withParameter: params];

Any idea, where my fault is?

Cheers, Martin