Diborane is the correct chemical. You're looking at the manufacture of diborane, not the combustion of it. The combustion of diborane is very exothermic and is what the government wanted to use back in the 50s and 60s. The problems with it were:
1. Diborane extremely toxic--more than HCN (hydrogen cyanide--the stuff they use to kill inmates in the gas chamber).
2. It explodes on contact with oxygen and has wide lower and upper explosive limits in air, making it very dangerous to work with.
3. It is pyrophoric--meaning it bursts into flame on contact with moisture in the air.
4. When it burns, it leaves behind solid boic acid and other oxides of boron, which clog the rocket nozzle.
To affect complete combusion the military tried adding fluorine to diborane to oxidize it all the way so no solids were formed, but this did not work well, and the project was abandoned. For many years afterword, boranes of all types were easy to get as surplus, but are no longer easy to come by.
I did a lot of work with diborane as an undergrad and have seen the beautiful (and scary) green flame that comes from the combustion of diborane. It is the second most energetic fuel by weight (after hydrogen) and was sought to be exploited by the government because of this.
As for making it, I won't detail that here because of the dangers involved and also because you probably can't get the chemicals. If you can and you really need to make this stuff for legit research purposes, then you'll know where to look up how to make it (not that hard to do).
I do like the amatuer rocket and pyro scene, but diborane is not for the faint of heart. That stuff will take you out. We used to call it 'death chemistry' only half-jokingly.
For some great stories about the government's rocket program, look up a book called "The Green Flame". It's written by a guy who used to work in the chemical industry producing boranes in the 1950's and is an incredible read. I think it's OOP, but you might still be able to find it in certain places.
The project cost more than a billion dollars in 1991 dollars, and some of the fatal accidents that occurred were extremely personal to me. Yet, I was so steeped in the mind-set of secrecy that I never considered that the story could be publicly told until 1985, 25 years after it ended. And by then I felt as if it absolutely had to be told. For one thing, it is totally contrary to the scientific method to spend a major amount of time and effort on a project and never reveal the full results and conclusions. Even a paleolithic hunter would feel obliged to tell his tribe where he had been and what he had seen. And those who died in the effort had some right to have the circumstances of their death revealed.
The boron fuels had three nasty tendencies, (1) all of them were highly toxic, requiring use of a gas mask for all hands-on operations, (2) most of them were pyrophoric, igniting in a vigorous green flame on contact with air, no spark required, and (3) they formed explosive mixtures with certain other compounds. We lost two of our men and our plant at Malta, NY, discovering one of those explosive combinations. After that, we built our plants in the Niagara Falls, NY, area. The work force in the Niagara Falls area grew to something on the order of 1,000 people and our company represented about half of the manufacturing effort, the other half being conducted at Callery, PA, Lawrence, KS, and Muskogee, OK, by Callery Chemical Co. Many others were involved in research, using materials provided by the manufacturing effort.
The employees were trying to dismantle scrap metal and a steel pipe with a torch when the flame unexpectedly struck a flammable substance, possibly wood grain alcohol residue, James said. "It ignited and exploded. A plume of smoke probably went up 30 feet from the structure," James said. At least three helicopters were called in to airlift the burn victims directly to Westchester Medical Center in Valhalla, where they were admitted late Monday afternoon.