Phospha-Fischer Carbenes: Synthesis, Structure, Bonding, and Reactions of Pd(0)− and Pt(0)−Phosphenium Complexes
Caputo, C., Jennings, M., Tuononen, H., & Jones, N. (2009). Phospha-Fischer Carbenes: Synthesis, Structure, Bonding, and Reactions of Pd(0)− and Pt(0)−Phosphenium Complexes. Organometallics, 28 (4), 990-1000. doi:10.1021/om800973v
DisciplineEpäorgaaninen ja analyyttinen kemia
© 2009 American Chemical Society. This is a final draft version of an article whose final and definitive form has been published by ACS. Published in this repository with the kind permission of the publisher.
The analogy between cationic group 10 metal−phosphenium complexes and Fischer carbenes has been formalized through structural and reactivity studies and by energy decomposition analysis (EDA) of the M−P bond. The studied compounds were the three-coordinate, 16-electron species [(NHPMes)M(PPh3)2]OTf (M = Pt (1) and Pd (2); [NHPMes]+ is the N-heterocyclic phosphenium (NHP) cation, [tiebar above startPN(2,4,6-Me3-C6H2)CH2CH2tiebar above endN(2,4,6-Me3-C6H2)]+, OTf = trifluoromethanesulfonate); these were made by reaction of [NHPMes]OTf with M(PPh3)4. The metal−phosphenium bond in both compounds was dominated by metal-to-ligand π-donation. This differed from the M−C bonds in the analogous N-heterocyclic carbene (NHC) complexes, (NHCMes)M(PPh3)2 (M = Pt (6), Pd (7)), which were instead predominantly σ-type. Structural determination of 1 by X-ray crystallography revealed the shortest yet reported Pt−P bond of 2.107(3) Å, consistent with significant double-bond character, and trigonal planar geometries at both the P-atom within the [NHPMes]+ ligand (∑(angles) = 359.99°) and at the Pt-atom (∑(angles) = 360.00°), which indicated that 1 was better described as a Pt(0)−phosphenium rather than as a Pt(II)−phosphide. Reactions of 1 and 2 with excess PMe3 cleanly gave the four-coordinate species [(NHPMes)M(PMe3)3]OTf (M = Pt (3) and Pd (4)), while reaction of 1 with bis(diphenylphosphino)ethane (dppe) gave [(NHPMes)Pt(dppe-κ2P)(dppe-κP)]OTf (5). Hydrolysis of these complexes resulted in metal hydrides and oxidation of the NHP to phosphine oxide via intial nucleophilic attack of water at the P-atom in the coordinated [NHPMes]+ ligand, which was calculated to bear a significantly positive charge in 1. ...