Three-coordinate geometries

Power and coworkers prepared the iron(V) bis-imide complex 3,5-Pr2 Ar Fe[N (1-Ad)]2l [42]. This complex has been characterized by X-ray crystallography with the iron in planar three-coordinate geometry. The Fe-N bond distances are 1.642(2) and 1.619(2)A. Magnetic studies of 3,5-Pr2 Ar Fe[N(l-Ad)]2 reveals that this complex has a low-spin cP configuration with S = jl ground state. This compound is notable as it is a stable Fe(V) imide being well characterized. 

The above-mentioned [Hg(P—Z-Bu2)2]2 has been obtained in a phosphide-transfer reaction between HgMe2 and Ga(P-z-Bu2)3. If CdMe2 and Ga(P—/-Bu2)3 are reacted, the product is the trimeric [MeCd(P-/-Bu2)2]3 with a six-membered Cd3P3 ring in twist-boat conformation and exocyclic Cd—Me bonds thus, Cd achieves near-planar, three-coordinate geometry. The Cd—P bond lengths in the ring are all similar (rav(Cd—P) 258.5 pm) in solution these Cd—P bonds... 

They are volatile in vacuo at 100 °C and dissolve in hydrocarbons the first three-coordinate lanthanide compounds to be characterized, they have congested three-coordinate geometries (Figure 4.9) due to the bulky SiMcs groups. They are pyramidal in the solid state with N-Ln-N angles around 114° rather than the 120° expected for a planar structure but they are evidently planar in solution as they have no dipole moment. Theoretical calculations (D.L. Clark et al, 2002 L. Penin et at, 2002) indicate that it is jS-Si-C agostic interactions with the lanthanide that are responsible for this small pyramidal distortion. 

Zn(TBT)2(Et20)l was prepared from the reaction of [Zn(CH2SiMe3)2] with 2 eq of HTBT in the presence of ether (98). The X-ray crystal structure shows the zinc to have a T-shaped planar three-coordinate geometry, with a S—Zn—S angle of about 160° and the shortest Zn—S... 

Reaction of the anion of dppm with MCI2 (M = Ge, Sn, Pb) forms complexes [CFI(PPh2)2]2M that exhibit three-coordinate geometry in the solid state, one ligand chelating through both... 

All three coordination geometries of silver tend to be labile to ligand exchange reactions, and this requires caution in measuring and interpreting chemical shift values. A classic example is the averaging of signals for [Ag(CN)2], [Ag(CN)3]2 and... 

The T2 (or normal ) copper site has an unusual three-coordinate geometry with two histidines and a hydroxide (or a water molecule, indistinguishable by X-ray) ligands. It exhibits EPR parameters typical of normal (aqueous) copper (A = 158-201 x 10 cm ) and no intense (charge-transfer) features in the visible absorption spectrum. 

Reaction of the orange solution of 54 with N3(l-Ad) in hexanes afforded dark red crystals of 3,5- Pr2-Ar Fe(N-Ad)2 (59) [144] (Fig. 16). It is noteworthy that 59 was the only isolated product when variable molar ratios of N3(l-Ad) to 54 were attempted. It is notable not only because it is the first stable Fe(V) imide, but it is also a very rare example of a well-characterized Fe(V) molecular species of any kind [147]. The iron has a planar three-coordinate geometry with interligand angles that have a maximum deviation of only ca. 1.4° from the idealized 120° trigonal planar value. The coordination planes at the imido nitrogens are almost coincident (maximum deviation 7.2°) with the central C(l)Fe(l)N(l)N(2) plane. 

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