Facial arrangement

Multidentate thioethers are readily introduced into the coordination sphere of low-valent cobalt. As an example, the tridentate thioethers 1,3,5-trithiacyclohexane and tris(methylthio)methane both replace three facially arranged carbonyl ligands in Co3(CO)9(/i-CPh), leaving the cluster otherwise intact.169... 

The related manganese(I) complexes of type /uc-[MnL(CO)3] (where L is one of the tetrathia macrocycles 1,4,7,10-tetrathiacyclododecane, 1,4,8-11-tetrathiacyclotetradecane, or 1,4,7,10,13-pentathiacyclopentadecane) were obtained by reaction of /hc-[Mn(CO)3(CH3COO)3] with L in acetonitrile. These species are readily decarbonylated with Me3NO to yield the corresponding ci5-[Mn(CO)2(L)]+ species. The facial arrangements in the products containing the 12- and 15-membered ring macrocycles were confirmed by X-ray structure determinations. 

Figure 2.8 Geometrical isomers. A) Meridial arrangement (Drew-Pfitzner structure). B) Facial arrangement (Pfeiffer-Schetty structure).

Isolation of the first examples of monomeric lanthanide alkoxides evidenced the importance of the a-effect . Use of a highly hindered phosphino-alkoxide ligand afforded mononuclear, 6-coordinated Ln(OCtBu2CH2PMe2)3 (Ln = Y, Nd) with facial arrangement of the bidentate ligands (Fig. 14, Table 8). The... 

The latter determination performed on a single crystal shows a rhenium(I) center in an octahedral environment with a facial arrangement of the three carbonyl ligands. The diphenylbis[(phenylthio)methyl] silane Ic forms a six-membered cycle with the rhenium center, in which the phenyl rings of the thioether groups are both orientated in the same direction as the bromide ligand. 

Rh(PMe3)2Cp]2+ would be equivalent to [(CO)Rh(PMe3)2Cp]2+, and [(q6-benzene)Mn(CO)3]+ would correspond to three CO ligands grouped in a facial arrangement on [MnfCOJJ. ... 

A single-crystal -ray analysis of (12) showed a partial meridional, partial cw-facial arrangement around five-co-ordinate phosphorus with a 40 % distortion toward rp along the co-ordinate from an idealized tbp and with the Cl group equatorial. The tendency of the three-co-ordinated nitrogen atom to achieve planarity is cited as the principal influence leading to the observed structure which, on the basis of n.m.r. evidence, is retained in solution. 

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