Which of the following reactions correctly represents the preparation of diborane?

Solution

1. The reaction $3{\text{NaBH}}_4+4{\text{BF}}_3\to 2{\text{B}}_2{\text{H}}_6+3{\text{NaBF}}_4$ is the primary industrial method.
2. The reaction $2{\text{NaBH}}_4+{\text{I}}_2\to {\text{B}}_2{\text{H}}_6+2\text{NaI}+{\text{H}}_2$ is a common laboratory preparation method.
3. Hence the answer is (C).