Bidentate phosphorus ligand, replacement

Addition of 2-butyne to [CpMo(dppe)2][PF6] displaces one dppe chelate to yield the cationic alkyne complex, [CpMo(dppe)(MeC=CMe)][PF6]-[Eq. (14)] (66). The replacement of a bidentate phosphorus ligand with a single 2-butyne donor is a comment on the propensity of Mo2+ to bind alkynes. 

CO groups in silyl-transition-metal carbonyls can be replaced by PR3 groups or bidentate phosphorus ligands ... 

The formation of chloroimino ligands has been proposed solely on weak v(C=N) vibrations in the 1600-1750 cm-1 IR region. A repeat of the vanadium reaction by other workers (109) found the product of their reaction to be VC13(CNBu )3, so some caution should be applied to the formulation of the proposed vanadium dimer at least. Substitution reactions on these compounds with a series of mono- and bidentate tertiary phosphorus ligands and metathetical replacements with lithium quinolin-8-olate and sodium diethyl dithiocarbamate have given a range of neutral and cationic products (204, 483). 

Bis[dw-butyLphosphano] tellurium replaces norbornadiene, cycloheptatriene, acetonitrile, and dimethyl(methylene)oxosulfurane in chromium, molybdenum, and tungsten complexes. The P —Te compound acts as a bidentate ligand with the two phosphorus atoms coordinated to the metal atom1. The tetracarbonylchromium complex [R = CH(CH3)J can be recrystallized without loss of tellurium2. 

Besides phosphines and phosphites preferentially used as ligands in hydro-formylation, phosphoramidites have also been proposed. Phosphoramidites (sometimes also called phosphoroamidites) are a class of organic phosphorus compounds derived from phosphites in which the P-OR groups have been replaced by P-NR2 groups (Figure 2.31). Three different P-substituents produce a chiral (stereogenic) phosphorus atom. Phosphoramidites play a crucial role in the synthesis of nucleic acids [1] and have also been frequently considered as mono- or bidentate ligands in transition-metal catalysis [2]. 

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