Back in Cambridge the going was a bit harder, because as I’ve explained earlier, I had to alter my planned course of action because it was already pre-empted to some extent by some Russian work. But I’d devised a new scheme of boron trifluoride coordination compounds: these are compounds which are formed between two molecules which themselves are stable. You have one molecule that can accept electrons and another which can donate electrons, and they stick together in that way, so it’s making and breaking of one bond. And this is a big branch of inorganic chemistry, particularly in transition metal chemistry where ligands as they’re called, donors like ammonia, can donate four or even six loan pairs into a central metal atom which is short of electrons.

I was not interested in the transition metals so much as the organic compounds, because I had in the back of my mind that this would be relevant to Friedel-Crafts catalysis. And so I thought of things like ether, diethyl ether which is two ethyl radicals joined on to an oxygen, and the oxygen has two pairs of electrons, in fact, but it can donate one to boron trifluoride which has only six electrons, and it would like to have eight in a simple octet approach to bonding.