Trigonal pyramidal structures phosphine

Phosphine Phosphine (PH3), a colorless, extremely poisonous gas, is the most important hydride of phosphorus. Like NH3, phosphine has a trigonal pyramidal structure and has the group 5A atom in the —3 oxidation state. Unlike NH3, however, its aqueous solutions are neutral, indicating that PH3 is a poor proton acceptor. In accord with the low electronegativity of phosphorus, phosphine is easily oxidized, burning in air to form phosphoric acid ... 

The nitrosyls RuH(NO)(PR3)3 are 5-coordinate with trigonal bipyramidal structures and linear Ru-N-O geometries the hydride and nitrosyl ligands occupy the apical positions (for RuH(NO)(PPh3)3, z/(Ru-H) 1970 cm-1, i/(N—O) 1640 cm-1 H NMR, 8 = +6.6 ppm for the hydride resonance). The high-field NMR line is a quartet showing coupling with three equivalent phosphines, which would not be possible in a square pyramidal... 

Bismuth phosphine complexes represent a substantial component of the established phosphine complexes of heavier p-block elements, and an excellent overview has presented an important bonding model for these systems (7). The observed structures are considered as trigonal-pyramidal BiX3 units with three secondary trans bonds. If the acceptor orbitals are the Bi-X trans arrangement is expected, as the relationship between the trans X-Bi-P bond distances. The shortest Bi-P distance [2.7614(2) vs 2.866(3) A] is trans to the longer Bi-Br distance [3.403(1) vs 2.9916(1) A], as the only arrangement that will allow the phosphine ligands to occupy trans... 

Five-coordination is often observed when CrCl3 forms numerous adducts with ethers, nitriles, amines, and phosphines, which have formulas CrCl3 2L or CrCl3 3L. An example is CrCl3 2NMe3 where X-ray studies confirm the trigonal bipyramidal structure with axial amine groups. The only known square pyramidal complex (17-C-Villa) is formed with the tetradentate macrocycle, tmtaa, (17-C-VIIIb).17... 

In the above compounds, the structural motif is the M4S4 cubane, but these closed structures will not incorporate three //2-sulfide bridges easily. A different self-assembly route leads to MoFe clusters that have a different composition but do contain a sulfur-voided cubane held by three //2-sulfides. The clusters MFe4S6Ls are shown as (15). Their Fe4(//3-S)3(//2-S)3 portions structurally resemble the part of the FeMoco farthest from molybdenum. These pentametallic clusters have been used to calibrate Fe EXAFS of the FeMoco. Another important aspect of these clusters is that three iron atoms have trigonal pyramidal geometry like the belt iron atoms of the FeMoco, with three sulfides in the basal positions and a phosphine in the axial position. A series of basket ... 

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