Treatment of Na2PdCI4 with 3-chloro-2-methyl-1-propene under an atmosphere of CO yields the dimer [(113- C4H7 )PdClb (A). The 1H NMR spectrum of A at 298 K shows 3 signals: a singlet at 0 2.2 and 2 doublets at 2.9 and 3.8 ppm with the relative intensities of the signals being 3:2:2 respectively. Addition of 2 moles of AsPh3 to the dimer A gives complex B (molar ratio As:Pd:CI = 1:1:1). 1H NMR spectrum of B at 195 K displays a singlet at 0 2.1 and 4 doublets at 0 2.7, 3.2, 3.6 and 4.5 with relative intensities 3:1:1:1:1 as well as aromatic protons due to AsPh3. On warming a solution of B the 1H NMR changes to show two singlets at 2.1 and 3.5 with relative intensities 3:4 in addition to resonances due to the aromatic protons.
(a) Give the structures of A and B and describe the bonding between the organic group and the palladium in A.
(b) Interpret and explain the NMR spectrum of A
(c) Interpret and explain the NMR spectrum of B at 195K
(d) Discuss what happens when B is warmed to 323K and how it accounts for the change in the NMR spectrum.
(e) How would you make the organic group in B more susceptible to nucleophilic attack.