gg Delta bonds: (d xy ± d xy ) or (d x2-y2 ± d x2-y2 ) (d xy + d xy ) or (d x2-y2 + d x2-y2 )
*u*u gg Delta bonds: (d xy ± d xy ) or (d x2-y2 ± d x2-y2 ) (d xy - d xy ) or (d x2-y2 - d x2-y2 ) (d xy + d xy ) or (d x2-y2 + d x2-y2 )
Bonding scheme for dimers of transition metal dications, M 2+ d g (z 2 ) u (xz, yz) g * (xz, yz) u * (xy, x 2 -y 2 ) g (xy, x 2 -y 2 ) d M 2+ M 2 4+ u * (z 2 )
Example: dimerization of Cr 2+ to form Cr 2 4+ d4d4 g (z 2 ) u (xz, yz) g * (xz, yz) u * (xy, x 2 -y 2 ) g (xy, x 2 -y 2 ) d4d4 Cr 2+ Cr 2 4+ u * (z 2 )
Example: dimerization of Cr 2+ to form Cr 2 4+ d4d4 g (z 2 ) u (xz, yz) g * (xz, yz) u * (xy, x 2 -y 2 ) g (xy, x 2 -y 2 ) d4d4 Cr 2+ Cr 2 4+ u * (z 2 ) Bond order = ½ (8-0)= 4 (quadruple bond!!!)
F. Albert Cotton…. King of multiple metal-metal bonds!!
Example: dimerization of Mn 2+ to form Mn 2 4+ d5d5 g (z 2 ) u (xz, yz) g * (xz, yz) u * (xy, x 2 -y 2 ) g (xy, x 2 -y 2 ) d5d5 Mn 2+ Mn 2 4+ u * (z 2 ) Bond order = ½ (10-0)= 5 (quintuple bond!!!)
Example: dimerization of Fe 2+ to form Fe 2 4+ d6d6 g (z 2 ) u (xz, yz) g * (xz, yz) u * (xy, x 2 -y 2 ) g (xy, x 2 -y 2 ) d6d6 Fe 2+ Fe 2 4+ u * (z 2 ) Bond order = ½ (10-2)= 4
Example: dimerization of Hg 2+ to form Hg 2 4+ d 10 g (z 2 ) u (xz, yz) g * (xz, yz) u * (xy, x 2 -y 2 ) g (xy, x 2 -y 2 ) d 10 Hg 2+ Hg 2 4+ u * (z 2 ) Bond order = ½ (10-10)= 0 (No bond!!)