Phosphines nitrogen donor ligands

The complexes [lr(COD)(NCMe)(PR3)]BF4 (PR3 = P Pr3, PMe3), which are closely related to Crabtree s catalyst, also contain mixed ligands, very basic phosphines, P Pr3 or PMe3, and a nitrogen donor ligand, acetonitrile. These mixed-ligand pair combinations have been shown to be very useful for spectroscopic observations and have provided detailed information on the mechanism of reactions performed by those complexes [9, 10]. 

Bis-nitrogen donor ligand-substituted alkylidyne complexes such as 78 were found to be good alternatives as starting materials to the thermally labile tetracarbonyl complexes 44). Substitution of one pyridine ligand in the bispyridine-substituted complexes 78 occurs in the presence of excess chloride [Eq. (64)] 103). The anionic complexes 79 are stable in the presence of excess chloride but are too labile to be isolated in pure form. These complexes were used in the synthesis of stable alkylidyne alkene tungsten complexes [Eq. (180), Section IV,G]. With phosphines both pyridine ligands in 78 are substituted [Eq. (65)] 44). For PMej the reaction of the tetracarbonyl complex W(CPh)Br(CO)4 had previously been shown to... 

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