Nature Communications 8: Article number: 14137 (2017); Published: 3 February 2017; Updated: 5 February 2018

The original version of this Article contained a typographical error in Fig. 2, where reagent H2C(Ph2PNSiMe3)2 was incorrectly given as H2C(PNSiMe3)2. This has now been corrected in both the PDF and HTML versions of the Article.