Analyse the geometric data

•	Sum the TRX2 angles by selecting Create... in the Parameters box on the left side of the Vista interface. This will generate a creating TRN10 window. Click on ANG2, then the + button, then ANG3 etc. Once you have done this for all of the TRX2 angles, i.e. summed all of the TRX2 angles, press OK.

 

•	This will create a new column in the table, labelled TRN10.

•	To plot the summed angle data as a histogram select the parameter TRN10 by clicking on the grey numbered button at the top of the relevant column, then select Histogram from the Data Visualization options on the right hand side of the window.

 

•	Inspect the histogram, what does this tell you about the preferred geometries of 4-coordinate transition metal complexes?

•	Structures with tetrahedral geometries can be found around 660 degrees in the histogram (6 x 109.5o) while the square planar structures are found close to 720 degrees (4 x 90o plus 2 x 120o).

•	Return to the spreadsheet window by clicking on RETURN.

•	To plot a scattergram of the summed angles versus ANG1 (the angle between the two TRX2 planes) click on the grey buttons above TRN10 and ANG1. This should highlight the appropriate columns. Then, select Scattergram, within the Data visualisation section on the right of the screen.

 

•	It is possible to link back to the original CSD entries by selecting data points in the scattergram then clicking on View Refcodes. What conclusions can you draw?

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The scattergram shows that most four coordinate complexes are either square planar (in the top left of the scattergram) or tetrahedral (bottom right). However this is not always clear cut, exemplified by the fact that there are many database entries linking the two geometries resulting in a continuum. Closer inspection of the structures which are neither square planar nor tetrahedral represent the interconversion between the two geometries e.g. CCXAPT, COBZAU, CMTUCU10.