Rectangular and Square Planar

Assembly of the orbital interaction diagram for rectangular H4 (D2h) from those of two H2 units. 

Consider what happens when the rectangular H4 molecule distorts to a square, that is, T becomes longer and r2 shorter (5.2). The overlap between H and H4 and 

An orbital correlation diagram associated with the H/D exchange for H2 + D2 proceeding via a square ( 4h) geometry. 

5 MOLECULAR ORBITAL CONSTRUCTION FROM FRAGMENT ORBITALS 

As shown in Chapter 4, there is always a choice to be made in writing degenerate wavefunctions. Recall that two new functions may be generated by taking a linear combination of the old. An alternative pair of wavefunctions is shown 

---

When the lactone (Chapter 9) 2H-pyran-2-one (2-oxo-2H-pyran, a-pyrone) is irradiated below 290 nm (with a pyrex filter to form a bicyclic lactone and, subsequently, without a filter to let in higher energy radiation) while frozen in an argon (Ar) matrix at 8 K, carbon dioxide (CO2) is eliminated and a species is formed whose IR spectrum (with only C-H and C-C bands and a weak band at 1523 cm ) is in concert with a rectangular (not square planar) structure. On warming, decomposition to dimer (mdo-tricyclo[2.0 . 0 ]octa-2,6-diene) and ethyne (acetylene, HC=CH) occurs. 

The Cu(PyrrolDtc)2 complex was found to be x-ray isomorphous to the square planar Ni(PyrrolDtc)2 complex (473). A structure determination of the former complex revealed a monomeric Cu(PyrrolDtc)2 unit with a square planar CuS4 chromophore (Table IX). This result is particularly interesting considering that the Cu(Et2Dtc)2 (53) and Cu(n-Pr2 Dtc)2 (507) complexes are dimeric species containing five-coordinate rectangular pyramidal Cu(II) ions. 

Planar SOFC, in particular, monolithic designs (MHI) are capable of high (volumetric) power densities most favoured by direct and short current paths across the stack components. The PEN is principally square, rectangular and circular (Ceramic Fuel Cells Limited (CFCL), Mitsubishi Materials Corp., SulzerHexis) in shape with active surface areas of 100-200 cm2 (15.5-31 in2). A drawback of this design is that it often necessitates the use of high temperature sealants for application at the in-... 

Problem 9.13 The energies of the -k m.o.s of monocyclic hydrocarbons of n atoms can be directly obtainedfrom the vertical coordinates of the corners ofan n-sided regular polygon inscribed in a circle of radius 2(3, with one corner at the lowest point see Fig. 9.9) ref. 121). Apply this construct to a square planar cyclobutadiene molecule the real geometry is rectangular) and conclude that this is not an aromatic hydrocarbon. 

Returning to our example, let us ask whether rectangular CBD can be expected to cross easily to the triplet as it approaches square-planar geometry. Applying Equation 9.33 to the overall irreps of the singlet and triplet in D2/1... 

Fig. 2. Schematic representation of the big + big distortion space of a square planar molecule. The center of the figure is the parent D41, structure. There are two different Dih epikemel symmetries points along the Qb,g distortion coordinate refer to rhombic structures with DihlCi) symmetry, while points on the distortion coordinate represent rectangular structures with DihlCJ) symmetry. All other points correspond to configurations with Qi, kernel symmetry. Remark that the Qbj and - Qbj distortions give rise to equivalent stmctures, and similary for the Qbj and - Qbj distortions. Hence eacfi epikemel point nas a multiplicity of two on the other hand, for each kernel point the number of equivalent distorted configurations is four - as illustrated by the black circles...

---