[slickfox]

I am trying to use chemical hardness to predict reactivity of Different Hydrides molecules and need some clarification:
Could somebody tell me why/check if my logic is correct and maybe add on
1. Switching B to Al will make it harder
   because Al is less electronegative (weakens bond)
2. Switching Na to Li will make it softer
   because Li is a stronger electron donor than Na
3. Switching H to O-alkyl (ie NaBH(OMe)3) will make it harder
   because more electronegative boron
4. Switching H to alkyl (NaBH(Me)3) will make it softer
    because electronegativity is lost

Could someone see if my trends above are even correct and help me to summarize them with stronger explanations?

 sources ive been using are
http://books.google.com/books?id=hAPoJsJ3jZsC&pg=PA93&lpg=PA93&dq=borohydride+1,4+addition+to+enone&source=bl&ots=_WEuddbQGe&sig=A73pch5rSsV23R_d9sb5iOJgJlU&hl=en&sa=X&ei=6I5SUpP7E8KViQL_mYHACg&ved=0CEMQ6AEwBA#v=onepage&q=borohydride%201%2C4%20addition%20to%20enone%20soft%20hard&f=false

http://books.google.com/books?id=vrITBZ-_jwEC&pg=PA536&lpg=PA536&dq=nabh4+reduction+of+enones&source=bl&ots=_RVzvXdD4H&sig=ajv30oVAIeb0JZbYTXPHZLi8sjE&hl=en&sa=X&ei=ZYZSUr7ZEKSiiQKEr4DIDQ&ved=0CF8Q6AEwBQ#v=onepage&q=nabh4%20reduction%20of%20enones&f=false

[slickfox]

Maybe it is easier to just think of reduction in terms of electronegativity

Li is a stronger reducer than Na because Li donates an electron more easily

Al is a stronger reducer because it has a weaker bond as a result Al being less electronegative than B

Alkyl substituents it a stronger reducing agent because they donate in electrons making the hydride opt to leave. (Also add sterics for stereoselectivitiy)

Electronegative substituents like CN and O-alkyl make the hydride less reactive as the try to pull in the negative charge on the hydride

Could someone check my logic. I'm taking a synth course that is almost exclusively reductions and I rogue memorization wont be enough to get by so I am establishing trends.

If anyone as studying methods for the reduction reactions please let me know. If I had to memorize something it would be about this much per week haha

http://www.chem.harvard.edu/groups/myers/handouts/1_Reduction.pdf

Thanks