TBP structure

Reaction of Ph4PCl with 0s04 gives Ph4P+0s04Cl, the anion having a tbp structure with a very long equatorial Os-Cl bond (2.76 A) [45]. 

Ru04 , which is believed to be tetrahedral in solution, is formed from Ru04 and excess concentrated aqueous KOH, isolable as black crystals of K2Ru04.H20, which is actually K2[Ru03(0H)2]. The anion has a tbp structure with axial OH groups (Ru=0 1.741-1.763 A, Ru—OH 2.028-2.040 A) [55],... 

They doubtless owe their stability to the bulk of the aryl thiolate ligand they have tbp structures with equatorial nitrile that can be displaced by CO to give rare carbonyls of a metal in the +4 oxidation state. 

M(NO)(OCOCF3)2(PPh3)2. Both these complexes have 5-coordinate geometries with monodentate carboxylates. The rhodium compound has a square pyramidal structure with bent Rh-N-O (122°) but the iridium compound has a tbp structure with straight equatorial Ir-N—O (178°). The position of i/(N—O) reflects this difference (1800 cm-1 (Ir) and 1665 cm-1 (Rh)). 

Diphenic acid (H2A) also forms diorganotin(IV) complexes, which are with two monodentate -COO groups. On the other hand, soluble dinuclear triorganotin(IV) complexes (where the organo moieties are Me and Ph) contain symmetrically bound carboxylates, while the less-soluble compound (cHexsSn) has two asymmetrically bonded carboxylates. All have Tbp structures with [RsSnirV)] units remote from each other. °... 

Structure, Bonding and Ligand Reorganisation. - An X-ray analysis of the monocyclic phosphorane (2) reveals a tbp structure with the hydrogen in an axial position and an H-P bond length of... 

Dopamine /3-hydroxylase (D/3H) is a copper-containing glycoprotein that hydroxylates dopamine at the benzylic position to norepinephrine.84 During the attempted crystallization of the bis(hydroxide)-bridged dicopper(II) dimer, a side product was subsequently isolated (complex (63)), revealing intramolecular hydroxylation at a formally benzylic position of the tris(imidazo-lyl)phosphine ligand.85 The copper(II) center has an axially compressed TBP structure. 

X-ray structure analyses of Rh(COCH3)(I)2(dppp) (14) and [Rh(I I)(I)(//-I)(dppp)]2 (15), where dppp l,3-bis(diphenylphosphino) propane, were reported. Unsaturated complex (14) possesses a distorted five-coordinate geometry that is intermediate between sbp and tbp structures.69 Under CO pressure, the rhodium/ionic-iodide system catalyzes either the reductive carbonylation of methyl formate into acetaldehyde or its homologation into methyl acetate. By using labeled methyl formate (H13C02CH3) it was shown that the carbonyl group of acetaldehyde or methyl acetate does not result from that of methyl formate.70... 

The TBP structures of 9 I2 and 11 2I2 are noteworthy, since iodine adducts of selenides are predicted to be MC based on the general rule (x(Se) (=2.48) > xCO (=2.21)). This must be the reflection of the high ability of the imidazoline ring to donate electrons to Se by the formation of the stable cyclic 6ji system. It will decrease xeff of Se in 9 and 11 to give TBP with iodine. Since the electronic conditions in 10 must not be so different from those in 9 and 11, they should not be responsible for the different structures of the adducts. This working hypothesis is supported by DFT calculations.38 Therefore, the crystal packing effect must play a crucial role in determining the structures of the iodine adducts of 9-11. The reactions are followed by spectroscopic and conductometric methods.37... 

To investigate whether a relationship exists between the solution structures of the hydridorhodium diphosphite species [RhH(CO)2(diphosphite)] [48] and catalytic performance, van Leeuwen and co-workers extensively studied the rhodium-diphosphite complexes formed under hydroformylation conditions by high-pressure NMR (HPNMR) techniques. It is well known that these complexes have a trigonal bipyramidal (TBP) structure. Two isomeric structures of these complexes, one containing the diphosphite coordinated in a bis-equatorial (ee) fashion and one containing the diphosphite in an equatorial-axial (ea) fashion, are possible (Fig. 4). 

The characterization of the rhodium complexes formed under hydroformylation conditions by NMR techniques and in situ IR spectroscopy showed that there is a relationship between the structure of the [HRh(CO)2 (BINAPHOS)] species and their enantiodiscriminating performance. Thus, (R,S)- and (S,R)-BINAPHOS ligands show high equatorial-axial (ea) coordination preference with the phosphite moiety in the axial position. Meanwhile, the characterization of the (R,R)- and (S,S)-BINAPHOS ligands suggests that there is either a structural deviation of the monohydride complexes from an ideal TBP structure or an equilibrium between isomers [20,34],... 

Gas electron-diffraction studies on the phosphoranes (77) and (78) have revealed that the former has a regular TBP structure with axial CFS groups, while the latter has a distorted TBP one.70... 

Preparative details and extensive i.r., n.m.r., and mass spectra have been described for the phosphoranes (87).48 These phosphoranes have a TBP structure, and for (87a)—(87c) their n.m.r. spectra are temperature-independent, and indicate that the fluorines bonded to phosphorus are equivalent. The authors have suggested an explanation based on rapid intramolecular isomerization, and discussed the possibility that a facile TR pathway exists for this process.46 Octahedral adduct formation between (87) and fluoride ion or trimethylphosphine has also been described,46 as shown in (88). 

Allyltrifluorophosphorane (89) may be prepared as shown, and the n.m.r. spectrum of (89) indicates a TBP structure.81 A similar route has been used to prepare the analogous arylphosphoranes (90), which have been found to be quite stable, and... 

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