Conformational metal-phosphine complexes

C, M. DiMeglio, K. J. Ahmed, L. A. Luck, E. E. Weltin, A. L. Rheingold, and C. H. Bushweller,/. Phys. Chem., 96, 8765 (1992). Stereodynamics of Sterically Crowded Metal-Phosphine Complexes fra s-[(r-Bu),P( -Pr)],MCl2 [M = Pt(II) and Pd(II)]. One-Dimensional Dynamic and Two-Dimensional Chemical Exchange NMR Studies. X-Ray Crystallographic Studies, Molecular Conformation Trapping, and Molecular Mechanics Calculations. 

M(nbdXCO)4 complex has also been reported,together with that of die related ditertiary phosphine complexes (7). Yields vary considerably, and in some reactions the ligands fail to chelate, giving M(CO)6 complexes as mqjor products. The njnj. spectra of the chelated complexes are interpreted in terms of rotamer populations of the ligands and conformational preferences of the chelate rings, and the effects of the systematic variation of donor atoms, metal atom, and solvent are discussed. 

Thereby, the presence of tertiary monophosphines is critical, because both polymeric (26) and cyclic tetrameric (24 and 25) complexes can be obtained depending on the phosphine added to the reaction mixture. Furthermore, with some of the phosphines rapid decomposition and deposition of metallic silver occurs. In the macrocyclic molecules 24 and 25 a pair of silver atoms is bridged by two bis(l-imidazolyl)borate moieties, with a transannular Ag Ag distance of 8.61 A for 24 and 8.89 A for 25. The conformations of 24 and 25 are... 

This chapter is concerned with the effects of nonbonded interactions in tertiary phosphine-transition-metal complexes on (a) cyclometallation and C-H activation and (b) the stability and conformations of large chelate rings. It also deals with how nonbonded interactions might be used in other areas of chemistry. 

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