Diastereoselective Assembling of 21-C-Alkylated Nickel(II) Complexes of Inverted Porphyrin on a Platinum(II) Template

Reaction of 21-C-methyl and 21-C-benzyl nickel(II) complexes of inverted meso-tetratolylporphyrin with platinum(II)
dichloride or its bis(benzonitrile) complex yields a chloroplatinum(II) species containing two nickel(II) carbaporphyrinoids
in a cis arrangement. One of the carbaporphyrinoids coordinates to the platinum ion with the external nitrogen
while the other is bound with the external nitrogen and one ortho-carbon of the adjacent meso-aryl ring. The
reaction is highly chemoselective. 1H and 13C NMR experiments in solution show the diastereoselectivity of the
reaction. Single-crystal X-ray data confirm the presence of the diastereomer with opposite configurations of the
Ni(II)-coordinated carbons in the subunits of the dimer. Cyclovoltammetric measurements reveal an anodic shift of
the nickel(II) oxidation potentials of dimers with respect to those of the parent monomers and two different reduction
couples. Reaction of unsubstituted inverted porphyrin with Pt(PhCN)2Cl2 in chlorobenzene yields a monomeric
platinum(II) complex of inverted porphyrin. This complex displays a markedly upfield 195Pt NMR shift compared to
tetraphenylporphyrinatoplatinum(II). Under strongly basic conditions deprotonation of the external nitrogen of inverted
porphyrin and both electrochemical and chemical oxidation of platinum(II) center are observed.