Phenyl ligands

An interesting example of a spin-admixed nonheme iron(lll) complex with S - (3/2, 5/2) ground state is the organometallic anion [Fe CeCls) which has four pentachloro phenyl ligands in tetrahedrally distorted planar symmetry [122]. 

The size of the ligand is crucial in deciding the degree of association, as shown by the very similar structural features of methyl- and "butyllithium derivatives. With hexameric structures in cyclohexane, the addition of diethyl ether affords tetramers in both cases. Further demonstrating the importance of the donor, the two-dimensional phenyl ligand also adopts a tetrameric structure in diethyl ether [Li(OEt2)Ph]4, which upon addition of the bidentate... 

A variety of catalytically active five-coordinate tungsten oxo and imido alkylidene complexes also have been prepared that contain some donor amine or pyridine linked either to the imido ligand or to a phenyl ligand bound to the metal (A, Scheme 2) [101-105]. Such species show metathesis activity (e.g., ROMP of norbornene),but there does not appear to be any proof that the integrity of the initiator is maintained. 

Several triphenylgermanium hydrides have been prepared where the hydride atom is encapsulated by substituents on the phenyl ligands,95,108-111 as illustrated in Equations (84)-(86).110,111 The germanium atom of 42a-c are formally hexacoordinate and that of 43 is heptacoordinate. A tribenzobarellenegermane compound with a trihydro-germane moiety attached to the bridgehead carbon was prepared and characterized (Equation (87)), and this species was found to be exceptionally air stable.1... 

DR. GEOFFROY Let me answer the last question first. I don t fully understand cis-methyl groups. When complexes containing those have been irradiated, one generally doesn t observe the formation of ethane. Instead, where the chemistry is well-defined, it looks as if solvolysis simply occurs to yield radicals. There are, however, some cases of diaryl complexes which, when irradiated, will couple two phenyl ligands to give biphenyl as a product. 

The proposed reaction mechanism is shown in Scheme 9.15. Starting from the phenyl-rhodium complex 87, alkyne rearrangement is expected to furnish the phenyl-vinylidene complex 88. Migration of a phenyl ligand onto the vinylidene moiety of 88 must occur such that the vinyl Rh-C bond and the enone tether of the resultant complex (89) attain a cis-relationship to one another. Intramolecular conjugate... 

The monoanionic potentially bidentate 2-[(dimethylamino)methyl]ferrocenyl ligand has coordinating properties similar to that of the 2-[(dimethylamino)methyl]phenyl ligand, and has also been used to stabilize a variety of organometallic derivatives. Bis [(2-dimethylamino)methyl]ferrocenyl magnesium (68) has been synthesized and was structurally characterized in the solid state by X-ray crystallography. 

While the mono-phenyl ligand, tro, is very much like trpy the tri-phenyl ligand, tsite, is quite different in its ruthenium complex. [Ru(tsite)2]2+ has a very intense lowest absorption band191-1, a somewhat higher quantum yield than [Ru(trpy)2]2+ (0.57 vs. 0.48 at 77 K), and is a room temperature emitter (lifetime about 0.2 (is). Unfortunately a room temperature quantum yield has not been reported for comparison with [Ru(bpy)3]2+. Our estimation of the quantum yield at room temperature from the reported lifetime is 0.01, a fraction of that reported for [Ru(bpy)3]2+. Thus, even in [Ru(tsite)2]2+, deactivation modes are more prominent than in [Ru(bpy)3]2+ and the above arguments are most likely applicable. 

Recently, Boche et al. (5) have reported the synthesis of a highly interesting crystalline adduct of 1,3-diphenylallyllithium with diethyl ether. The crystal structure of this complex (I in Fig. 1) shows symmetrical it bonding between lithium atoms and allylic fragments. Each lithium atom interacts with two allylic 7t systems and further with the oxygen atom of a diethyl ether molecule. An exo, exo orientation of the phenyl ligands has been observed in this coordination polymer. 

Recently, structural evidence for the first quintuple bond between two metal atoms was found in the dichromium(I) complex Ar CrCrAt7 (where Ar is the sterically encumbering monovalent 2,6-bis[(2,6-diisopropyl)phenyl]phenyl ligand). This complex exists as air- and moisture-sensitive dark-red crystals that remain stable up to 200°C. X-ray diffraction revealed a centrosymmet-ric molecule with a planar trans-bent C-Cr-Cr-C backbone with measured structural parameters Cr-Cr 183.51(4) pm, Cr-C 213.1(1) pm, and C-Cr-Cr 102.78(3)°. Characterization of the compound is further substantiated by magnetic and spectroscopic data, as well as theoretical computations. Figure 19.2.6 shows the molecular geometry and structural formula of Ar CrCrAr. ... 

---