Is There A Difference Between "Impending" And "Imminent"?

They both mean something predicted to arrive.  So imminent can denote something closer or more urgent but not necessarily expected.
For example: because he was rarely at work and was constantly out to lunch his dismissal was imminent.

However if we talk about a person and need an adjective to describe their forthcomming success, we would say, an emminent politician.
Impending can be used in the following ways, and generally denotes something long awaited or looming on the horizon.
So: John and Lucy's impending marriage was making them nervous.
Or, the impending Olympic Bid results had everyone very excited.
The impending deadline for my article, has me concerned.
The difference may seem slight, as with so many terms and adjectives in the English language, but that is what makes it such a specific language, and is the reason I am so passionate about it, and am glad it is my mother tongue.