Multiple covalent bonds orbital overlap

The pi bond A multiple covalent bond consists of one sigma bond and at least one pi bond. A pi bond, represented by the Greek letter pi (tv), forms when parallel orbitals overlap and share electrons. The shared electron pair of a pi bond occupies the space above and below the line that represents where the two atoms are joined together. 

Orbitals overlap directly in sigma bonds. Parallel orbitals overlap in pi bonds. A single covalent bond is a sigma bond but multiple covalent bonds are made of both sigma and pi bonds. 

Recall from Section 8.1 that multiple covalent bonds consist of one sigma bond and one or more pi bonds. Only the two electrons in the sigma bond occupy hybrid orbitals such as sp and sp. The remaining unhybridized p orbitals overlap to form pi bonds. It is important to note that single, double, and triple covalent bonds contain only one hybrid orbital. Thus, CO2, with two double bonds, forms sp hybrid orbitals. 

Multiple Covalent Bonds— End-to-end overlap of orbitals produces a (sigma) bonds. Side-to-side overlap of two p orbitals produces a tt (pi) bond. Single covalent bonds are double bond consists of one o- bond and one 77 bond (Fig. 11-15). A triple bond consists of one a-bond and two v bonds (Fig. 11-17). The geometric shape of a species determines the o--bond framework, and tt bonds are added as required to complete the bonding description. 

The Mode of Orbital Overlap and the Types of Covalent Bonds Single and Multiple Bonds Mode of Overlap and Molecular Properties... 

To describe multiple bonding, we must consider a second kind of bond lhat results from the overlap between two p orbitals oriented perpendicularly to Ihe intemuclear axis (Figure 9.22 ). This side-to-side overlap o/p orbitals produces a pi (77) bond. A 77 bond is a covalent bond in which e overlap regions lie above and below Ihe intemuclear axis. Unlike a a bond, in a 77 bond Ihere is no probability of finding the electron on tire intemuclear axis. Because Ihe total overlap in the 77 bonds tends to be less than that in a [Pg.338]

Cyclopentadienyl (Cp) complexes (see Cyclopentadienyl) are known for almost all the metals of the periodic chart, including technetium. The compounds with transition metals usually possess covalent jt Cp M bonding. The nature of the metal Cp bond is multiple. The <7-bond is formed from the overlap of an empty d orbital of Tc with one of the frUed jt bonding molecular orbital on Cp with good symmetry. Back-donation is usually also present from the filled d orbitals of Tc to one of the empty n molecular orbitals on Cp. These molecules are usually called sandwich compounds (see Sandwich Compound), when there are two Cp ligands bonded to the metal, or half-sandwich complexes (see Half-sandwich Complexes) when only one Cp ligand is present. 

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