Non fluxionality

These nano-objects display an organometalhc surface chemistry comparable to usual organometalhc moieties and which can be studied by classical spectroscopic methods substitution reactions leading to structural changes in the particles, the fluxional or non-fluxional behavior of surface hgands, the formation and observation of surface hydride species, the monitoring of catalytic reactions etc. 

Thermolysis of (cycloheptatrienylmethyl)carbene complexes 554 [toluene, 1-2 h, 80-100°C MLn = Cr(CO)5, W(CO)5] affords an equilibrium mixture of 4,5-homotropilidenes 555 and 556. According to the NMR data and the results of AMI calculations, the formation of isomer 556 (equation 218) is strongly favored277. This course of events was called intramolecular cyclopropanation , and it was shown that the equilibrium between the 4,5-homotropilidene complexes is significantly different from that of the metal-free ligands. By reaction of the latter (555 and 556) with bis(ethylene)rhodium 1,3-pentanedionate 557, the complexes 558 and 559 of both 4,5-homotropilidenes were obtained in a 1 3 ratio. These complexes are non-fluxional and are configurationally stable at room temperature (equation 219)277. 

Synthesis of the pale yellow dimer [Rh2 P(OMe)3 8] has been reported via ligand displacement from [CpRh(C2H4)2] (Cp = cyclopentadienyl) using excess P(OMe)3 at 60°C.115 Its 31P n.m.r. spectrum at room temperature indicates the non-fluxional bicapped trigonal antiprismatic structure (26). However, at 100 °C the spectrum is... 

Whilst reaction of acyl chloride 303 with Na[Co(CO)3(PEt3)] affords the oxocyclobut-enyl complex 306" by ring expansion and CO loss, analogous treatment with NaRe(CO)5 delivers the non-fluxional // -cyclopropenylrhenium compound 305" . In the latter case, compound 304 loses carbon monoxide with concomitant migration of the cyclopropenyl moiety from carbonyl to rhenium as an allylic rearrangement rather than a 1,2-shift. 

Mono-anionic ligand derivatives [Rh6(CO)i5L] (L = H, halide or pseudo halide) also have the structure shown in Fig. 5a NMR measurements (Table 3) show that their structure in solution is consistent with their static structure and, apart from [HRh6(CO)i5] , vide infra, are non-fluxional at room temperature. 

Complexes IrH2(BH4)L2, where L is a bulky tertiary phosphine, have been prepared. They are the first examples of metal-hydroborate complexes in which the BH4 ligand is non-fluxional. Thus, the structure is (5), and H n.m.r. signals were seen separately for the bridge and terminal hydrogen atoms. °... 

Scheme 12), but absence of it in 18, where 18 can be considered as based on a non-fluxional tetrahedron or octahedron. A theoretical analysis of the allyl fluxionality in 17 and 18 has recently been published. Formation of an 7] -allyl allows an alternative to rotation for interconversion of exo- and endodi.ovneK and characterized by interchange of syn- and /(-protons. This is a well-documented process which is particularly important in asymmetric catalysis using Pd allyls (Scheme J3) 1 >16,76,77... 

Non-fluxional vinylic boranes do not react with carbonyl compounds. Nevertheless, the vinylic borane 29 reacts with acetone (2 h under reflux) yielding the Z-isomer of the homoallylic borinic ester 30b. The cw-configuration of the reaction product 30b corresponds to the following sequence of transformations (Scheme 2.11). The [1,7]-H shift in the vinylic borane 29 gives the allylic Z, Z-isomer 28d which immediately reacts with acetone before the equilibrium among the allylic isomers is established. On the other hand, cyclopentanone reacts directly with 29 under mild conditions yielding Z, Z-1,3,5-heptatriene 31 and borinic ester 32 (Scheme 2.12). Apparently 29 reacts with the enol form of cyclopentanone, and a direct splitting of the B-Q ,2 bond takes place. Similar reaction of 29 with acetic acid was used for the preparative synthesis of previously unknown hydrocarbon 31 (Scheme 2.12) [35]. 

CI2CH)2Sn.xTHF results from LiCHCl2 and SnCl2 and has been characterised as a stannylene. However SnClj and Me Si(Me2P)2 Li give not the stannylene but the non-fluxional spiro-Sn(II) complex... 

The synthesis of a trinuclear cyclopentadienyl trihydrido complex having carbonyl ligands had been reported prior to the synthesis of 6 and 7. Treatment of (CpRu)2(CO)2( -CO)( -CHR) 17 with H2 (1 atm) under UV irradiation provides fluxional complex 18. The fluxionality involves the passage of tj-CsHs and CO ligands from one side of the Ru3 plane to the other. Protonation of 18 yields a non-fluxional cation 19 in which all three cyclopentadienyl ligands are on the same side of the RU3 plane (Equation (3)). Compound 18 has been shown to react readily with a wide... 

The fluxional behaviour of [Cp2Mo2(CO)4(2-propylnorbornyl)J [BF4]- has been rationalised 27 by comparison with the non-fluxional analogue [CpMoCo(CO)5(2-propylnorbomyl)]+. 

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