Coordination intramolecular

For practical reasons, (his chapter is divided into sections describing compounds with relatively simple intramolecular coordination involving lew intramolecular. cwis bases (9.8.1) and those in which polydentate ligands, mostly polyethers, are involved with (9.8.2) or without intramolecular coordination (9.8.4). 

The most simple form of intramolecular coordination involves ulkoxy or alkylamino side arms as 

In both 39 and 40. the bridging X in a dimer of type 4 is an amido nitrogen. Compound 39 193J has two independent molecules in the unit cell with practically identical slructures (Mg-C 2.10 A, Mg-N(amido) 2.10 A. Mg-N(umino)  

Compound 47 has a rather symmetrical structure with the linear Ht-Mg lit unit (Mg-C 2.10 A) 

Another interesting feature of polydemale ligands is their tendency to fully cleave the polar magnesium carbon bond with formation of solvated cations and inagnesate counterions. In this regard, there is a remarkable difference between 15-crown-5 and 18-croun-0 while the latter 

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I. Omae, Organometallic Intramolecular Coordination Compounds, Elsevier, Amsterdam, 1986. 

The heavier chalcogens are more prone towards secondary interactions than sulfur. In particular, the chemistry of tellurium has numerous examples of intramolecular coordination in derivatives such as diazenes, Schiff bases, pyridines, amines, and carbonylic compounds. The oxidation state of the chalcogen is also influential sulfur(IV) centres engender stronger interactions than sulfur(II). For example, the thiazocine derivative 15.9 displays a S N distance that is markedly longer than that in the corresponding sulfoxide 15.10 (2.97 A V5. 2.75-2.83 A, respectively). ... 

Intramolecular chalcogen interactions may also stabilize reactive functional groups enabling the isolation of otherwise unstable species or their use as transient intermediates, especially in the case of selenium and tellurium. For example, tellurium(II) compounds of the type ArTeCl are unstable with respect to disproportionation in the absence of such interactions. The diazene derivative 15.23 is stabilized by a Te N interaction. Presumably, intramolecular coordination hinders the disproportionation process. Other derivatives of the type RTeX that are stabilized by a Te N interaction include 8-(dimethylamino)-l-(naphthyl)tellurium bromide, 2-(bromotelluro)-A-(p-tolyl)benzylamine, and 2-[(dimethylammo)methyl]phenyltellunum iodide. Intramolecular donation from a nitrogen donor can also be used to stabilize the Se-I functionality in related compounds." ... 

Transannular Te N interactions have also been employed to stabilize compounds of the type 15.24 with terminal Te=E (E = S, Se) bonds.The Te=Se bond length in 15.24b is 2.44 A (cf. 2.54 A for a Te-S single bond) and d(Te N) = 2.62 A. Intramolecular coordination was also employed in the isolation of the first aryl-selenenium and -tellurenium cations 15.25a,b as [PEg] salts. 

Although bulky aryl groups, e.g., mesityl, are not effective in stabilizing arylselenium (II) azides, the use of intramolecular coordination in 2-Mc2NCH2C6H4SeN3 has enabled the first structural characterization of this reactive functionality. The Se-Ns (azide) bond length is 2.11 A, while the intramolecular Se N distance is 2.20 A, cf. 2.14 A in the arylselenium bromide 15.5, and 2.13 A and 2.17 A, respectively, in the corresponding chloride and iodide. This... 

The stmcture of the compound 67b was determined by X-ray (95JA6388). The length of the Te=Se bond (2.445 A) is 0.1 A shorter that in bis(2-ethylcarboxy-phenyltellurenyl) selenide (81CSC1353), which points to a greater double bond character of this bond in the former compound. Selenoxide 67b has a boat conformation. The length of the transannular Te- N bond (2.620 A) is appreciably shorter than the corresponding van der Waals contact (3.70 A). The intramolecular coordination Te- N bond thus formed contributes to the stabilization of the boat conformation of the compounds 67. 

Molecular and crystal structures of the macroheterocycle 102 were studied by X-ray [96JCS(D)1203]. As for bis-imines of di(o-formylphenyl) telluride 106, [89MI1 91JOM(402)331] only one of two potentially possible intramolecular coordination N Te bonds exists in a molecule of the macrocycle 102, which, in... 

Hypercoordinated derivatives of P,0-heterocycles with intramolecular coordination by donor groups 98EJI1847. 

Structure and reactivity of chelates due to intramolecular coordination of hy-pervalent type 99MI6. 

Organometallic intramolecular-coordination compounds containing a nitrogen donor ligand. 

Organometallic intramolecular coordination compounds containing a phosphorus donor ligand. I. Omae, Coord. Chem. Rev., 1980, 32, 235-271 (168). 

Intramolecular coordination in organic derivatives of non-transition elements. A. K. Prokofev, Russ. Chem. Rev. (Engl. Transl.), 1976,45, 519-543 (331). 

Cyclization of an organolithium tethered to a suitably positioned carbon-carbon jt-bond is a thermodynamically favorable process that proceeds in a totally regioselective exo-fashion with a high degree of stereocontrol via a transition state in which the lithium atom is intramolecularly coordinated with the remote rc-bond.9 The stereochemical outcome of the cyclization of a substituted 5-hexenyllithium follows from the preference of the substituent to occupy a pseudoequatorial position in the chair-like transition state depicted below.7... 

Intramolecularly Coordinated Cations As cations, intra- or inter-... 

The mercury atom is four-coordinate, both nitrogen atoms being involved in intramolecular coordination. The reaction of (Cabc,N)SnMe2Br with Na afforded the bis(o-carboranylamino)distannane [(Cabc,N)SnMe2]2 53. The two tin atoms exhibit approximately trigonal-bipyramidal geometry. 

The concept of intramolecular coordination by the use of C, Y-chelating ligands of aryl units has been well established. However, the analogous chemistry of its cousin, the three-dimensional carborane, remains relatively unexplored. Recently, o-carborane has attracted much interest due to its ease of preparation and derivati-zation, thermal stability, and steric bulk. The easy preparation of o-carborane can be utilized for preparing useful compounds similar to the C, Y-chelating ligands of... 

Until recently, there have been only two examples of stable Ge-S double bond compounds and one each for Ge-Se and GE-Te double bond compounds, but both of them are stabilized by the intramolecular coordination of a nitrogen ligand to the germanium center. 

Meanwhile, Parkin and his co-workers have also reportedthe synthesis of a series of terminal chalcogenido complexes of germanium 66, 67, and 68 (Scheme 20).42 X-ray structural analyses of 66, 67, and 68 revealed that they have unique germa-chalcogenourea structures stabilized by the intramolecular coordination of nitrogen atoms. The central Ge-X (X = S, Se, Te) bond of 66, 67, and 68 should be represented by a resonance structure, Ge+ - X- —>- Ge=X, because their bond... 

It should be noted that all the M=X bond lengths observed here are significantly shorter than those reported for the corresponding double bond compounds stabilized by intramolecular coordination of heteroatoms. In other words,... 

Reinhoudt et al. [174] reported the self-assembly of an AB2 type of monomer 83 with two Pd centers. Labile coordinating ligand, acetonitrile, when removed by heating from a solution of nitromethane in vacuo initiated an intramolecular coordination of benzylnitrile group with the tridentate Pd-centers leading to a hyperbranched structure. Coordination of the benzylnitrile group was moni-... 

Intramolecularly coordinated A1 and In compounds (e.g., (75), (76)) transfer the Me group in cross-coupling reactions with various aryl halides, including chlorides, catalyzed by Pd and Ni complexes.16 262 265 Monoorganobismuth compounds are reactive in cross-coupling reactions only if they contain an intramolecularly coordinating residue (77),266 267... 

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