High Reactivity of (P,N)Pd(methyl)+ Derivatives toward Mixtures of CO and Norbornene

The reactivity of cationic (P,N)PdMe(CO) + (P,N = Ph 2 P- o -C 6 H 4 CH 2 NMe 2, Me 2 N- o -C 6 H 4 CH 2 PPh 2, 1-(dimethylamino)-8-(diphenylphosphino)naphthalene; anion, - B[3,5-Ph(CF 3 ) 2 ] 4 ) toward CO and norbornene is described. CO and norbornene insert slowly into the palladium−methyl bond to yield (P,N)Pd[C(O)Me] + and [-3-methyl-2-norbornyl] + derivatives. Compounds (P,N)PdMe(CO) + react fast with mixtures of CO and norbornene under formation of (P,N)Pd[C 7 H 10 C(O)Me] + and two isomers of (P,N)Pd[C 7 H 10 C(O)C 7 H 10 Me] + . The dissimilarity in rates is explained in a kinetic model, wherein reactive intermediates are reversibly formed and trapped by norbornene in case of trans-P (P,N)Pd[C(O)Me] + and CO in case of trans-P (P,N)Pd(C 7 H 10 Me) + complexes. CO insertion into the Pd−alkyl bond takes place in the trans-N Pd−alkyl complexes, and norbornene inserts into the Pd−acyl bond from the trans-P Pd−acyl complexes. Isomerization from trans-P to trans-N in (P,N)Pd[C(O)Me] + is slow with respect to CO deinsertion and subsequent norbornene insertion into the trans-P (P,N)Pd + −acyl bond. Fast and reversible trans-N-to-P isomerization is found in compounds (P,N)Pd[C(O)-3-Me-2-C 7 H 10 ] + .