Silane ligand bonding

In all complexes of the CpL2Mn(H)SiR3 family, except 4, the silane is bonded to the metal only by the three-center bond (type K). Contrary to this, the agostic C—H bond in all known complexes with M—H—C three-center bonds is part of a ligand, which is also classically bonded to the same metal at another coordination site (type L ), either by a covalent bond or a 7r-bond (as in 21) or by a metal-metal bond (as in 22). Although this difference probably has no influence on the principal characteristics of the three-center bond, it may be very important with respect to the stability... 

Hexachloroplatinic acid in isopropanol (Speier s catalyst) is the most commonly used hydrosilylation catalyst because of its broad applicability and effectiveness at very low concentrations. A generally accepted mechanism for homogeneous platinum catalysed hydrosilylation involves reduction of Pt(IV) to Pt(II) by the silane, ligand substitution by the alkene, oxidative addition of SiH to the metal, rearrangement to a a-bonded complex and finally reductive elimination of the product and recycle of the catalyst 206 208. The basic mechanism is summarised in Scheme 2. 

The application of classical and non-classical (photoacoustic) reaction-solution calorimetry to probe the energetics of metal-ligand bonds in organometallic systems is briefly analysed and illustrated by thermochemical results involving two families of compounds. The classical reaction-solution studies enabled the discussion of the systematics of metal-carbon bond enthalpies in several complexes M(t) -C H ) L. The photoacoustic studies addressed the effect of phenyl goups on the energetics of silicon-hydrogen bonds in phenyl-substituted silanes. 

Waals fadtus of the silane ligand or by dosest-ht dis rams described by Berendson (lOS) but permits the preparation of silica based anion ex> clipngeia wiA sey limes th lunptioiial groups that are currently available op bonded silicgrbased supports. 

Acid Hydrolysis of Bonded Phases. One of the problems encountered with acid hydrolysis of silane-bonded phases Is that dimerization of the silane ligands Is favored (42), as Illustrated In Reaction 1 of Figure 1 and Table I. Such dimerization can be helpful for the... 

---