Donor-acceptor complexes of Ge, Sn and Pb

Some donor-acceptor complexes containing Ge-Ge and Sn-Sn bonds are listed in Table 14.7.2. 

The compounds listed in Table 14.7.2 have the formal formula which indicate the presence of a M=M double bond, but the measured M-M bond lengths vary over a wide range. The M2C4 (or M2Si4) skeleton is not planar, in contrast with that of an olefin. Thus the properties of the formal M=M bonds are diverse and interesting. Two examples listed in this table are discussed below. 

As reference data, the normal values M-M single-bond lengths are calculated from the covalent radii (Table 3.4.3) and the normal bond lengths of M=M double bonds are estimated as 0.9 x (single-bond lengths). Thus the 

Structure of the R2Sn— SnCl2 (R = ( ll (Si Me ( i 11(, ). (a) Molecular structure (the SiMe3 groups have been omitted for clarity), (b) the lone pah-forming a donor—acceptor bond. 

Sn-Sn bonding model in [Sn CH(SiMe3)2h]2 (a) overlap of atomic orbitals, (b) representation of the donor-acceptor bonding. 

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