Seven-coordinate complex, reaction

The results described above can be accounted for by the sequence of reactions outlined in Scheme I. Insertion into the C-D bonds of C D presumably yields the seven-coordinate complex 1. This reaction must be readily reversible since the NMR and IR experiments detailed above indicate that it leads to H/D exchange to produce [ReD ppe ] and C D H. The ready reversibility of this reaction presumably obtains because of severe steric crowding in 1 in which there are nine phenyl groups located around the central Re atom. [ReH ppe ] also undergoes... 

The unique seven-coordinate complex [TcO(EDTA)] is obtained by reaction of [TcOCy with H4EDTA in anhydrous dmso. The X-ray crystal structure confirmed pentagonal-bipyrami-dal geometry, with the 0x0 group and the two nitrogen donors bound in the equatorial plane. " All other structurally characterized technetium complexes with polyamino-polycarboxylates are in oxidation state IV. 

Another type of complex in which Tc C bonds predominate is the seven-coordinate complex [Tc(CNR)gX] + (398) (R = variety of organic groups X = C1, Br). The compounds are easily prepared in good yield by reaction of the Tc complex [Tc(CNR)6] " with Br2 or CI2 in acetonitrile. Attempts to introduce a bipy ligand as well led to dealkylation of the isocyanide to give the seven-coordinate complex [Tc(CNR)5(CN)X]+ (399). Reductive coupling of the coordinated isocyanides was attempted, but the reduction of Tc to Tc was the only reaction." ... 

Reduction of Re (terpy)2Cl" is irreversible and re-forms Re (terpy)2 in a two-electron reaction. Other seven-coordinate complexes [e.g. Re (bpy)3 (CNBu ) +] are generated in this manner and exhibit similar reactivity [31]. 

Oxidation of ris-[W(CO)2(diphos)2] with I2 leads to the unexpected one electron oxidation product [W(CO)2(diphos)2]+. This paramagnetic complex exhibits only one carbonyl stretching frequency, indicating a trans stereochemistry.307 Reaction of [W(CO)4diars] with excess bromine also results in the seven-coordinate complex [W(CO)3(diars)Br2]+, which appears to be a Win derivative.308 It is unusual that three carbonyls are retained by the metal in this oxidation state. 

The reaction of Mo02(MeNHOi2 in the presence of the hydroxylamine ligand and CS2 proceeds according to Scheme 4. 4 The resultant formally seven-coordinate complex has a distorted pentagonal bipyramidal structure with the lone oxo group in the apical position. The five equatorial positions are occupied by two formally bidentate 0,N hydroxylamido ligands of... 

D. Synthesis and Reactions with Donor Ligands of the Highly Versatile Seven-Coordinate Complexes [MX2(CO)3(NCMe)2] (M = Mo, W ... 

In 1977, a paper14 giving a molecular orbital exploration of structure, stereochemistry, and reaction dynamics of seven-coordinate complexes was published. 

Tripathi et al.56-51 have described the reactions of [W(CO)5(amine)] and [W(CO)4(amine)2] (amine = butylamine, cyclohexylamine, piperidine, morpholine) with an equimolar amount of X2 (X = Br, I) to afford the oxidized species [WX2(CO)4(amine)J, and [WX2(CO)3(amine)2], respectively. In 1983, Moss and Smith58 described the reactions of [M(CO),(py)] (M = Mo, W) with X2 (X = Br, I) to give the anionic seven-coordinate complexes [pyH][MX3(CO)4], which upon reaction with bipy give the neutral complexes [MX2(CO)3(bipy)]. 

Baker et al. have described the synthesis and reactions with donor ligands of the molybdenum complexes [MoClI(CO)3(NCMe)2])6° and [MoBrI(CO)3(NCMe)2],161 which are prepared by reaction offac-[Mo(CO)3 (NCMe)3]101 with C1I or BrI, respectively. Reaction of [M(CO)4(N N)J (M = Mo, W N N = bipy, phen) with ICN affords the seven-coordinate complexes [M](CN)(CO)3(N N)].162... 

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