Clusters trigonal bipyramidal

A crystalline compound [Na(crypt)]+2Pbs]2 has been prepared183 in which [Pb5]2 , 94, is a trigonal bipyramidal cluster the structure of which has been characterized by X-ray diffraction, with Pb-Pb distances of 3.00-3.22 A [crypt = N(CH2CH2OCH2CH20CH2CH2)3N]. See Section I.B for analogous tin compounds. 

The NMR spectra of Pbs and Sn5 have not been reported even though the clusters were first isolated in 1975 [40]. Preliminary data for Pb5 ion show that it is static on the NMR time scale (Fig. 4) [41]. The Dsh structure of the trigonal bipyramidal cluster is expected to give rise to two NMR resonances. While only one resonance has been located (5 ° Pb = -3,591 ppm), it clearly shows coupling to a second inequivalent set of Pb atoms with j( Pb- ° Pb = 2,344 Hz). The calculated intensity distribution for the three equatorial Pb nuclei is expected to be 0.004 0.28 1 0.28 0.004, whereas the signal for the two axial Pb atoms is expected to be 0.054 0.387 1 0.387 0.054. Although it is difficult to compare the observed line intensities for the assignment, experimental data are closer to the... 

A series of trigonal bipyramidal clusters of the general formula [M2Nia(CO),6] (M = Cr, Mo, W) were prepared by Dahl and co-workers (134) via the reaction shown in Eq. (32). 

Unfortunately, application of this rule is severely limited by the fact that the correspondence of polyhedra between polyboranes and carboranes with metal clusters is confined to the square pyramid, the trigonal bipyramid, and the octahedron moreover, the rule fails to account for the 76 electrons of the known trigonal bipyramidal clusters (Table VI). 

Polynuclear platinum and palladium carbonyl clusters containing the bulky tri-ferf-butylphosphine ligand are inherently electron-deficient at the metal centers. The trigonal bipyramidal cluster [Pt3Re2(CO)6(P Bu3)3], as shown in Fig. 11.4.4(a), is electronically unsaturated with a deficit of 10 valence electrons, as it needs 72 valence electrons to satisfy an 18-electron configuration at... 

Two recent examples of 9 are provided by HgPt3(dppm)3CO and HgPt3(dppm)3Hg in which there are tetrahedral and trigonal bipyramidal clusters of metal atoms.120... 

Figure 74. Trigonal bipyramidal cluster [Fe (tmphen)2]3[M (CN)6]2 (M =Fe, Co) viewed approximately along the axis of the TBP. Intramolecular n-n contacts are shown with black arrows [Adapted from (174).]...

Fig. 9.3 The Zintl ion [Sn5p has a trigonal bipyramidal cluster structure.

Co3Nig(pg-C), tetracapped square antlprlsm. Fluxlonal trigonal bipyramidal clusters CRh Pt(CO) ] " (n 14,12 with, respectively 76 and 72 valence electrons) are in equilibrium in solution and have... 

Rh—Rh 2.730—2.741(< 1) equatorial-equatorial, 2.923—3.032(< 1) axial-equatorial, trigonal-bipyramidal cluster... 

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