The synthesis and characterization of several Pt(ii) complexes, including formyl complexes, based on the PCP-type pincer ligands C6H 4[CH2P(iPr)2]2 (iPrPCP) and C6H4[CH2P(tBu)2]2 (tBuPCP) are described. The chloride complex (iPrPCP)PtCl (6) and the unsaturated cationic complexes [(PCP)Pt]+X- (X = OTf-, BF4-) (1, 7), based on both PCP ligands, were prepared and the latter reacted with carbon monoxide to give the corresponding cationic carbonyl complexes [(PCP)Pt(CO)]+X- (X = OTf-, BF4-) (2, 8a). Hydride nucleophilic attack on both carbonyl complexes resulted in rare neutral platinum formyl complexes (iPrPCP)Pt(CHO) (3) and (tBuPCP)Pt(CHO) (9). Complex 3 undergoes decarbonylation to the corresponding hydride complex within hours at room temperature, while the bulkier complex 9 is more stable and undergoes complete decarbonylation only after 3-4 d. This observation demonstrates the very significant steric effect of the ligand on stabilization of the corresponding formyl complexes. Reaction of complex 9 with triflic acid resulted in the carbonyl complex [(tBuPCP)Pt(CO)]+ OTf- (8b) with liberation of H2, an unusual transformation for a metal formyl. Reaction with methyl triflate resulted in the Fischer carbene-type complex, the methoxy-methylidene [(tBuPCP)Pt(CHOCH 3)]+OTf- (11). The X-ray structures of complexes 2, 6, 8a and 11 were determined.
ASJC Scopus subject areas
- Inorganic Chemistry