The article The Threshold Theory Regarding Creativity and Intelligence: An Empirical Test with Gifted and Nongifted Children found results that do not support this "Threshold Theory" of creativity.
Results of divergent thinking tests (administered to 228 intermediate school students, of whom about 43 percent were gifted) and calculated correlations between creativity and intelligence measures did not support the threshold theory which posits that creativity and intelligence are related only up to an intelligence quotient of about 120.
Can Only Intelligent People Be Creative? A Meta-Analysis by Kyung Hee Kim found a negligible correlation of IQ and creativity and does not support the Threshold Theory.
The mean correlation coefficient was small (r = .174; 95% CI = .165 – .183), but heterogeneous; this correlation coefficient indicates that the relationship between creativity test scores and IQ scores is negligible. Age contributed to the relationship between intelligence and creativity the most; different creativity tests contributed to it secondly. This study does not support threshold theory.
Several studies dispute the claims of Threshold Theory but the most interesting is probably Biochemical Support for the “Threshold” Theory of Creativity: A Magnetic Resonance Spectroscopy Study which appears to show some support for the idea in a fairly rigorous biochemical method.
There is at best contentious support for the threshold theory, and perhaps more importantly the association between creativity and IQ seems rather weak.