new obj-c syntax fail (or maybe im just using it wrong)

gistfile1.m

NSDictionary *songDict = @{@"artists": [item valueForProperty: MPMediaItemPropertyArtist],
                           @"title":   [item valueForProperty: MPMediaItemPropertyTitle]};

// ----------- vs ---------- //
// the new syntax above caused a memory error. i ended up just using the old syntax below and the code worked fine
// ----------- vs ---------- //

NSDictionary *songDict = [[NSDictionary alloc] initWithObjectsAndKeys:
                          [item valueForProperty: MPMediaItemPropertyTitle],              @"title",
                          [item valueForProperty: MPMediaItemPropertyArtist],             @"artists",
                          nil];