Germanium-silicon bonds, lengths

Phosphorus, Arsenic, and Silicon and Germanium Porphyrins M—N Bond Length and Degree of Ruffling"... 

A bond between two lead atoms is found46 in hexamethyl dilead, Pbj(CH ) . The Pb—Pb bond length, 2.88 0.03 A, is about that expected from the tetrahedral radius of lead, as is the Pb—C bond length, 2.25 0.0G A. This substance is, of course, similar to hexa-methyletham and the corresponding compounds of silicon, germanium, and tin. 

Silicon and germanium have been found to form clathrate-type host lattices in which guest species are alkali atoms. The host lattices are exactly the same as those of type 1 and II hydrates "" (see 16.2.2). They are formed by atoms of only one kind, which are bonded together by strongly covalent forces, as in the Si or Ge diamond structures. The Si—Si or Ge—Ge bond lengths are of the same order of magnitude as in classical Si or Ge with the bond angles 109°28 which characterizes the tetrahedral sp hybridization of the carbon family. 

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