Silicon-carbon system

Meerson GA (1966) Investigations of some hard alloys in the boron-silicon-carbon system. Mod Develop Powder Met, Proc Int Powder Met Conf 3 95 Dokukina IV, Kalinina AA, Sokhor MI, Shanurai FI (1967) Izv Akad Nauk SSSR, Neorg Mater 3 630... 

Figure 3. Phase diagram of the silicon-carbon system at 1 bar total pressure after Kleykamp and Schumacher [12].

Akad. Nauk BSSR, 10(10), 778-782 (1966) (Phase Relations, Phase Diagram, Review) [1966Schl] Schuermann, E., Hirsch, J., Contributions to the Heterogeneous Equilibrium of Iron-Silicon-Carbon System (in German), Giesserei Tech.-Wiss. Beih., 18(1), 1-16 (1966) (Experimental, Phase Diagram, 29)... 

Despite the differing levels of calculations, the same general conclusions were reached. The silicon-carbon double bonds in 1-silaallene (1.69 A) and 2-silaallene (1.70 A) are shorter than in isolated silenes at the same level of theory. This trend is also observed in the analogous carbon series. 1-Silaallene is thermodynamically more stable than 2-silaallene by 21 kcal/mol (22). Intuitively, this is what would have been expected, realizing the low ability of silicon to participate in multiple bonds. As may be expected from simpler systems (i.e., H2Si=CH2)(i97), silylene isomers (for example, structures 8 and 9) are considerably more stable (approximately IS kcal/mol) than their silaallene counterparts. 

It is likely that more silicon-carbon bonds are produced by the hydrosilylation of olefins than by any other method except the direct process. This deceptively simple addition of an Si-H bond to a C-C multiple bond can be promoted by a variety of means, but transition metal catalysis is by far the most significant. Two relatively old catalysts, H2PtCl6 ( Speier s catalyst ) and Pt2(Me2ViSiOSiMe2Vi)3 ( Karstedt s catalyst ), remain the most effective, and the remarkable rates and turnover numbers observed in these systems are among the most impressive in all of organometallic chemistry. The bulk of the literature on hydrosilylation falls outside the scope of this review, and readers are directed to the comprehensive work on hydrosilylation edited by Marciniec.93... 

Silicon—Carbon Thermoset. The Sycar resins of Hercules are silicon—carbon thermosets cured through the hydrosilation of silicon hydride and silicon vinyl groups with a trace amount of platinum catalyst. The material is a fast-cure system (< 15 min at 180°C) and shows low moisture absorption that outperforms conventional thermosets such as polyimides and epoxies. Furthermore, the Sycar material provides excellent mechanical and physical properties used in printed wiring board (PWB) laminates and encapsulants such as flow coatable or glob-top coating of chip-on-board type applications. 

The activity of these particular groupings probably arises in part from the distance between the nitrogen atom and the hydrocarbon branch (at the silicon atom). A similar structure-activity relationship has also been noted in carbon systems (60). However, the silicon-nitrogen system may assume a cyclic conformation in which the unshared electrons of the nitrogen are coordinated with the d orbitals of the silicon atom (14). The potential for such a structural feature does not exist in most carbon systems. Silicon-to-nitrogen coordination is an important feature of the silatranes (61, 62), although physical evidence for such coordination in open-chain silylalkylamines is lacking (52). 

X HE USE OF CHEMICAL APPROACHES to improve the processing, properties, and performance of advanced ceramic materials is a rapidly growing area of research and development. One approach involves the preparation of organometallic polymer precursors and their controlled pyrolysis to ceramic materials. This chapter will review the preparation and application of silicon-, carbon-, and nitrogen-containing polymer systems. However, the discussion is not exhaustive the focus is on systems with historical significance or that demonstrate key technological advances. 

Experimental data as well as calculations 284, 330) reveal two important differences between silicon-carbon bonds and carbon-carbon bonds, i.e., torsional barriers are small and gauche interactions unimportant for the Si—C bond when compared to the C—C bond. Low torsional barriers may imply a more flexible system (lower barriers to ring inversion), and small gauche interactions may imply lack of substituent preference or low substituent preference when compared to the parent carbocycle. Although calculations for heavier Group IV heteroatoms have not been published, it is probable that results will be similar to those obtained for Si. 

Z5.4 SILICON ATTACHED TO ADJACENT PARTICIPATING ir-BONDED CARBON SYSTEMS... 

Included in the term nonoxide ceramics are all non-electrically conducting materials in the boron-carbon-silicon-aluminum system. The industrially most important representatives, apart from carbon (see Section 5.7.4), are silicon carbide (SiC), silicon nitride (Si3N4), boron carbide (B4C), boron nitride (BN) and aluminum nitride (AIN). 

Introducing the Triazole Rina. The final step of the synthesis was displacement of the carbon-bound chlorine with triazole salts. Once again, silicon made life easy for us, since it activates such hindered systems toward displacement. The corresponding all-carbon compounds react very sluggishly with triazole salts. Luckily, silicon-carbon bond cleavage is not observed, provided water or other oxygen nucleophiles are excluded. The displacement reaction is illustrated in Equation 5 for DPX-H6573. 

ZnBr2 also work as an effective catalyst for the carbonyl insertion into 187b (Scheme 10.253) [684]. The Zn-catalyzed system is valuable for insertion of aldehydes and ketones (including aliphatic compounds) as well as formates. In sharp contrast to the Cu-catalyzed reaction, the zinc-catalyzed reaction inserts these carbonyl compounds into the less substituted silicon-carbon bond of 187b with high... 

The adhesives curing after polycondensation reaction also include silicones. Here, systems between organic and inorganic compounds (Section 2.2.5, Figure 2.4) are concerned. In their basic structure they have silicon-oxygen bonds instead of carbon chains ... 

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