What is 'R' as shown in the figure?

[navneet9431]

what are those 'R' atoms(highlighted in red)?
Also,What is finely divided Nickel(marked in red)?
I will be thankful for help!
Note:I am a High School student and English is my second language!

 

[DrDu]

R="Rest", is a generic abbreviation for that part of the molecule which is not explicitely drawn, e.g., an ethyl group. "Finely divided" means a very fine powder which has a high specific surface.

 

[navneet9431]

R="Rest", is a generic abbreviation for that part of the molecule which is not explicitely drawn, e.g., an ethyl group. "Finely divided" means a very fine powder which has a high specific surface.

Thank you!

 

[symbolipoint]

Usually a hydrocarbon branch