Cone angle of phosphine

Cone angles of phosphines are discussed in Chapter IS. The cone angles of P(OPh)j. P(CHiCH2CN)j, and PPh3 are 128", 132°, and I45B, respectively. 

The cone is created by the surface that encloses all the Ugand atoms for all orientations resulting from the rotation around the metal-phosphorus bond. The cone angles of phosphines and phosphites can span a very wide range, e.g., the cone angles of PMe Ph, PPhj, and P(Bu )2Ph are about 120°, 150°, and 170°, respectively. 

The Pt—P (and Pt—Cl) bond lengths correlate with the electron-donating ability of the phosphine (Tolman s Xi factor) rather than steric factors (the cone angle of the tertiary phosphine) [150b]. 

The cone angles of optical isomers are, of course, identical, but it has been demonstrated that chiral phosphines in homogenous catalytic systems can determine a reaction pathway to form asymmetric products.199 Clearly the chirality of the phosphine is the determining factor in these systems, although other essential characteristics of the phosphine ligand s bulk and the it acidity still... 

Graph 1. The relationship between the barrier to 2-butyne rotation (AGt) and the cone angle of the phosphine ligand in the series of complexes [WEiCCPLil-rp-MeCiMe)] L -PMe3, PMe,Ph, PMePh2, PPh3(0) PEt, PEt-Ph, PEtPh, PPh,(X). [Reproduced with permission from J. Chem. Soc., Dalton Trans. 1989, 299.]... 

Murahashi and Naota studied the reaction mechanism of cyclopentadienyl ruthenium enolate complex-catalyzed aldol and Michael addition reactions [80-82]. This mechanistic study revealed that the cone angle of the tertiary phosphine ligands largely affects the stability of C- and N-bound complexes [80, 82], Thus, ligation of bulky phosphine ligand would favor the N -bound complexes [80]... 

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