Bond properties hypercoordinate

Silatranes 1 are meanwhile classical cage compounds with donor-acceptor interactions and represent examples of hypercoordinated silicon [2], The donor-acceptor contact in 1 is formed by an interaction of the Lewis-basic amino group with the Lewis-acidic silicon center favored by the chelate effect. Numerous examples show that electron-rich transition metal complexes also possess Lewis-basic properties [3, 4]. Isolobal replacement of the NR3-unit in 1 by a d ML4-unit [5] leads to compounds of type 2 [1,6, 7]. These Si/Ni-cages 2 can be regarded as metallosilatranes. Here we report on the s5mthesis, structure and bonding of 2. 

Heterocycles with endo- and exo Si-Si multiple bonds 04YGK94. Hydrazide-based hypercoordinate silicon compounds (Si-helates) 04MI4. Organometallic complexes of silicon analogs of azoles 03AHC(85)1. Relationship between photophysical properties and conformation of cyclic oligosi-lanes with two or more silicon atoms 02YGK762. 

A property of main group atoms which have the ability to acquire coordination numbers greater than 4 (which would comply with the Lewis octet rule). Hypercoordination may be associated with hypervalency, but usually is referred to peculiar atomic centers in electron-deficient species with multicenter cr-bonding, in which pairs of electrons are spread over more than two atoms. 

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