Key Concepts

Question 1

electronic properties of phosphine ligands

Answer 1

stronger R = more e- rich MC, more pi-back to CO 2pi*, weaker CO with lower stretching freq

Question 2

e- rich metal centre if

Answer 2

low metal oxi state, strongly EDG ligands and heavier metals

Question 3

pi-back donation

Answer 3

donation from filled metal t2g to CO empty pi* orbital, e- density placed into strongly ABMO, weaker CO bond with lower stretching freq

Question 4

add of H2 to metal

Answer 4

oxidative addition, heterolytic cleavage and s-bond metathesis

Question 5

heterolytic cleavage

Answer 5

needs base

Question 6

s-bond metathesis

Answer 6

exchange of H-H and M-R bonds, characteristic of d0 metal

Question 7

oxidative addition requirements

Answer 7

accessible higher metal ox state, empty metal coord site and non-polar substrates for cis product

Question 8

how is H-H bond broken

Answer 8

s-donation from H2 sg to vacant s-MLn depopulates H2 BMO
pi-back donation from occupied metal t2g ti H2 su* ABMO further weakens bond