Organometallic Chemistry of Groups 14 & 15 Flashcards

Flashcards on the organometallic chemistry of Group 14 and 15 elements, covering stability, preparation, reactions, and structural aspects.

Stability of Group 14 Organometallic Compounds

Group 14 compounds are generally much more stable than group 13 and group 15 compounds.

Preparation of Group 14 Organometallic Compounds

Prepared using Grignard reagents or directly from elements, for example: 4PbNa + RCl → R4Pb + 4Pb + 4NaCl

Reactions of Silicon Compounds

Electrophiles cleave the bond in the presence of a Lewis Acid, e.g., (CH3)4Si + HCl → (CH3)3SiCl + CH4 with AlCl3.

Cleavage of Aryl vs. Alkyl Groups in Silanes

Aryl groups are more easily cleaved than alkyl groups.

Relative Rate of Cleavage of M-Ph Bond

The rate increases in the order Si < Ge < Sn < Pb for the reaction R3MPh + HA → PhH + R3MA.

Silicon Halide Isolability

Only isolable products with fluorides are obtainable due to rapid hydrolysis with other halides (Cl, Br, I).

Bond Energies of Si-F vs. Si-O vs. Si-Cl

Bond Energy (Si-F) > Bond Energy (Si-O), Bond Energy (Si – Cl) < Bond energy (Si-O)

Adduct Formation of Sn Compounds

They can form adducts that can be isolated such as SnCl2(CH3)2(DMSO)2 or Sn(CH3)3Cl(Py).

Hydrolysis Products of Ge Compounds

Hydrolysis of Ge, Sn, and Pb compounds can lead to [(CH3)3Ge]2O or [(CH3)2GeO]n.

Single Bond Energies in Group 14

Single bond energies decrease going down Group 14.

Stability of Organopolysilanes

They are stable thermally, hydrolytically, and oxidatively due to low mobility and reactivity of R and Ph groups compared to H

Stabilization of MR2 Compounds

Bulky R groups, such as ((CH3)3Si)2CH, are needed to produce isolable MR2 compounds.

Structure and Properties of Ge, Sn, and Pb Monomers and Dimers

Monomers have a lone pair in an sp2 hybrid plus an empty p orbital; dimers form through donor-acceptor interactions.

Summary of MR2 Compounds

Unstable kinetically to disproportionation and polymerization; monomers in benzene and vapor, but dimers in solid-state.

General properties of Group 15 compounds

ER3 and ER5 with increasing stability of the III state going down the group. P3E=O shows a strong formal double bond.

Preparation of PR3 Compounds

Prepared from PCl3 + 3RMgCl → PR3 + 3MgCl2 or PCl3 + ArCl + 6Na → PAr3 + 6NaCl.

Hardness (Lewis) of the Group 15 compounds

Reactivity order: N> P> As> Sb>> Bi with hard acids

Preparations of mixed compounds in Group 15

R2Cd + 2PCl3 → 2RPCl2 + CdCl2, HC≡CH + AsCl3 → HClC=CHAsCl2, C6H6 + PCl3 + AlCl3 → PhPCl2

Reactions of alkyldichlorophosphines

RPCl2 + Nu → RPNu2 (Nu = H, OR’, SR’ NR’2 etc) RPCl2 + H2O → RP(O)OH RPCl2 + Cl2 →RPCl4

Arsenic reactions

Several reactions lead to RAsO(OH)2, RAsH2, R2AsO-OH, R3As are are key reactions

Properties of Antimony and Bismuth Compounds

Antimony forms (CH3)3Sb, a powerful reducing agent, while Bismuth favors the III oxidation state.