Metal vapor synthesis complexes

It is in the synthesis of organometallic complexes that the metal-atom technique shows its greatest utility. From metal vapors, many complexes may be synthesized on a macroscale that are difficult, if not impossible, to prepare by standard, wet-chemical techniques (64, 65). In this section, we shall illustrate the vast potential that the method has in this area, although, to be sure, it is evident throughout this entire review. 

Co-condensation of Hf and Zr atoms from an electron-gun evaporation device, with P(Me)3 and arenes at 77K gave good yields of the species [M(arene)2P(Me3)]. Metal vapor synthesis led to Fe(i7 -arene)L2 and Fe(i7 -arene)-(i7 -diene), where L is a phosphorus ligand. In addition, complexes of stoichiometry Fe(T) -diene)L3 (where L is again a... 

Dihydro-lH-l,5,2-azasilaboroles derive from the 2,5-dihydro-lH-l,2-aza-boroles ( 6.5.3.3) by substitution of the carbon neighboring N by a silicon atom. They may act as four-electron donors using electron density from the C=C double bond and the N atom. The B atom behaves as an acceptor center. Two pathways are known for complex synthesis reaction with a generated transition-metal complex fragment and reaction with metal atoms by the metal-vapor synthesis method. 

Azaborolyl sandwich complexes can be prepared by metal-vapor synthesis ( 6.5.3.1) ... 

Dihydro-l,2-azaborolyl sandwich complexes, available by metal-vapor synthesis ( 6.5.3.3), can be prepared in a greater variety by reaction of metal halides with azaborolyl anions, e.g. " ° ... 

Cloke et al. presented the elegant metal-vapor synthesis for the preparation of linear 14 valence-electron complexes [M°(NHC)2] 73 (M = Ni, Pd, Pt) (Fig. 24a) [186]. The method was subsequently improved [187] and the interesting electronic and catalytic properties of Pd° and Pt° biscarbene complexes have been studied in detail [188-191]. 

Bis(amido) phosphine-donor complexes, with Zr(IV), 4, 816 Bis(amido) pyridines, with Zr(IV) and Hf(IV), 4, 790 Bis(aminoalkylidyne) complexes, diiron carbonyl complexes with cyclopentadienyl ligands, 6, 248-251 Bisaminosilylenes, in molybdenum carbonyls, 5, 406 Bis(tj-arc nc) complexes, as metal vapor synthesis milestone, 1, 236... 

Cobalt-silicon bonds, in hydridocobalt complexes, 7, 5 Cobalt—tin bonds, in hydridocobalt complexes, 7, 5 Co-catalyst effects, in olefin polymerization, 4, 1111 (—)-Goccinine, via Alder-ene reactions, 10, 593 Co-condensation sites, in metal vapor synthesis technique,... 

Electron-beam heating, in metal vapor synthesis, 1, 232 Electron-beam vaporization, in metal vapor synthesis, 1, 224 Electron correlation, and computational chemistry, 1, 642 Electron counting, in transition metal complexes bridging ligands, 1, 14 examples, 1, 9 ligand electrons, 1, 5/... 

M-M bonded compounds, 4, 131 in monoolefin polymerization, 4, 141 Europium(II) complexes, alkyl compounds, 4, 4 Europocenes, characteristics, 4, 27 Evaporation rates, in metal vapor synthesis, 1, 225 Ewen s symmetry rules, for olefin polymerization stereocontrol, 4, 1023 Exchange reactions... 

Heteroalkenes, with iron, 6, 132 Heteroannulation, allylic benzylamines, 10, 156 Heteroarene chromium carbonyls, preparation and characteristics, 5, 260 Heteroarenes borylation, 10, 242 C—H functionalizations, 10, 127 as metal vapor synthesis milestone, 1, 237 with titanium, 4, 246 vanadium complexes, 5, 48 7]6-Heteroarenes, with platinum, 8, 664 Heteroaromatic compounds... 

Lanthanide triflates, for allylic tin reactions, 9, 354 Laser beam heating, in metal vapor synthesis, 1, 224 Laser methods, in mechanistic studies, 1, 248 Laser photochemical vapor deposition, with organometallic complexes, 1, 259... 

W. M. Lamanna, Metal Vapor Synthesis of a Novel Triple-Decker Sandwich Complex (p6-Mesitylene)2( J,-p6 6-mesitylene)Cr2, J. Am. Chem. Soc. 108, 2096-2097 (1986). 

Cocondensation of nickel atoms, generated by metal vapor synthesis techniques with t-BuC=P, affords equal amounts of the isomeric sandwich complexes 94 and 95. The former compound features an T -phosphirenyl ligand in addition to an T -l -triphospholyl ring, whereas in 95 the metal is sandwiched between two i74-l,3-diphosphete units see Eq. (19).5,c... 

Not surprisingly, in recent years the technique of metal vapor synthesis, in which the metal vapor and PF3 are cocondensed at liquid nitrogen temperatures, has found general application since PF3 is readily condensible (in contrast to CO) and the high volatility of the resulting metal-PF3 complexes facilitates their isolation (method H). 

The most generally applicable route to diene or triene metal PF3 complexes is via metal vapor synthesis (method D), in which the metal vapors are cocondensed with PF3 and the polyene at liquid nitrogen temperatures. 

The [Ni(alkene)(PF3)3] complexes (alkene = C1CH=CH2, CH3CH= CH2, CF3CH=CH2, and FCH=CH2) made by metal vapor synthesis are much less thermally stable than the polyene complexes (28) and decompose readily to give [Ni(PF3)J, alkene, and nickel metal. 

The metal vapor synthesis can also be used to obtain bisarenemetal complexes, which then readily react with PF3 to displace one arene ring (method C). This route has been used effectively in the synthesis of [Cr( 6-naphthalene)(PF3)3] (225, 226) (Scheme 6). 

Addition of PF3 to an 5-heptadienyl metal PF3 complex can lead to the corresponding f/3-allylic complex (method I). Finally, the method of metal vapor synthesis (see Sections IX and X) has not found general application for allylic systems (method J), but in one case, cocondensation of Fe, PF3, and [Sn(allyl)4] gave the unstable paramagnetic complex [Fe(PF3)3( /3-allyl)]. 

More recent developments have utilized metal vapor synthesis (method F) involving cocondensation at low temperature of the metal, cyclopentadiene (or other dienes), and PF3. The hydrido-cyclooctadienyl complex [Cr( 5-C8Hn)(PF3)3H] 125) (see Section IX) made in this fashion exhibits variable-temperature NMR spectra which establish the existence of an exchange between the hydrido atom and a methylenic hydrogen bound to an sp3 carbon adjacent to the diene unit. 

An alternative synthetic procedure is to use Metal Vapor Synthesis (MVS) (see Metal Vapor Synthesis of Transition Metal Compounds). This method of preparation is hindered by the high boiling point of molybdenum and the expense of the MVS apparatus. It does, however, allow a greater range of functionalized bis-a.rene complexes to be synthesized. ... 

Arene complexes are usually prepared by the following methods (i) metal vapor synthesis (see Metal Vapor Synthesis of Transition Metal Compounds).(ii) AEAIX3 reduction of a metal halide in the presence of the arene and (hi) alkyne cyclotrimerization (see Cyclodimerization -tri-merization Reactions). Synthetic procedmes to obtain r] -arene derivatives have been reviewed by Pampaloni and Calderazzo. Over the past ten years, studies in this... 

Re arene complexes also result from application of the MVS technique to the extremely refractory Re metal (see Metal Vapor Synthesis of Transition Metal... 

There are just few examples of authentic lanthanide complexes in the oxidation state zero. Bis(arene) complexes of the lanthanides (l,3,5- Bu3C6H3)2Ln (Ln = Sc, Y, La, Nd, Pr, Sm, Gd, Tb, Dy, Ho, Er, Lu) have been synthesized by cocondensation of metal vapors (see Metal Vapor Synthesis of Transition Metal Compounds) with 1,3,5-tri(ferf-butyl)benzene at 75 K. A sandwich structure with coplanar arene ligands has been proven by X-ray crystal structure analysis of the Gd and Ho complexes (Figure 86a). 

The homoleptic (see Homoleptic Compound) titanium diene complex (j " -r-BuCH=CHCH=CHBu-t)2Ti (11) has been prepared by the condensation ofelectron-beam vaporized titanium with an excess of 1,4-di-t-butylbuta-1,3-diene" (see Metal Vapor Synthesis of Transition Metal Compounds). The bis-diene dmpe complex Ti(dmpe)( " -C4H6)2Ti (12) has been prepared by the reduction of TiCl4(dmpe) with Na/Hg in the presence of butadiene, and by the reduction of TiCLi with CH2=CHLi in the presence of dmpe. ... 

---