Bond lengths hydride complexes

Figure 2.68 Bond lengths in two 5-coordinate rhodium hydride complexes with bulky tertiary...

They display the considerable trans-influence of hydride and aryl groups (the Pt-Cl bond lengths should be compared with the value of c. 2.31 A in PtCl4 ). The Pt-P bond lengths are more insensitive to the phosphine, but by synthesis of ds-Pt(PR3)(PR3)Cl2 [150] complexes, it has been possible to study the effect of electron-withdrawing substituents on the Pt-P bond, as well as on the trans-influence of the phosphine (Figure 3.94). 

The X-ray structure of 83 was in accord with the prediction of Scheme 4 in that the Si-Cl bond lies in the niobocene bisecting plane trans to the hydride and is elongated compared with classical complexes of the type [M(SiR2Cl)L ]. There was, however, no good reference system that would allow for the comparison of the Nb-Si bond lengths. The metal-silyl bond lengths are strongly affected by Bent s... 

Mean cobalt-cobalt and nickel-nickel distances observed in these complexes are very close to interatomic distances determined at ambient temperatures in cobalt and nickel metals (Co-Co 2.489(7) A vs. 2.507 A in a-cobalt (33) Ni-Ni 2.469(6) A vs. 2.492 A in the metal (39)). The mean M-H bond lengths, as well as hydride displacements from M3 faces, are less for nickel in H3Ni4(Cp)4 than for cobalt in HFeCo3(CO)9(P(OMe)3)3. Although the differences are marginally significant within error limits (Ni-H 1.691(8) A vs. Co-H 1.734(4) A displacements from plane Ni3 0.90(3) A vs. Co3 0.978(3) A), they are in the expected direction since the covalent radius should vary inversely with atomic number within a transition series. However, other effects such as the number of electrons in the cluster also can influence these dimensions. 

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