<b>A Molecular Orbital Theory for Square Planar Metal Complexes</b>

Gray, Harry B.; Ballhausen, C. J.

doi:10.1021/ja00886a002

Cited by 435 publications

(119 citation statements)

References 2 publications

(3 reference statements)

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“…Our c.d. energy since it is stabilized by overlap with the results are consistent with his views and those of 4p, orbital (1).…”

supporting

confidence: 89%

“…The ordering of the d-orbitals given for [Ni(CN),I2-may not necessarily be valid for [Pd(CN),I2-and [Pt(CN),I2-since the crystal field strength of ligands coordinated to second and third row transition metals is usually greater than that observed for transition metals of the first row. As a result, the levels of dZ2 and d,, may reverse to yield the arrangement given by Gray and Ballhausen (1). These other complexes absorb at much higher energies and have large extinction coefficients so that the technique which we have used is not readily applicable.…”

mentioning

confidence: 94%

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Circular dichroism of the tetracyanonickelate(II) ion

Haines¹,

Smith²

1968

Can. J. Chem.

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When [Ni(CN),IZ-is dissolved in optically active 1,2-propanediol, two circular dichroism bands are observed which can be attributed to electronic transitions in the complex. Based on previous molecular orbital calculations, the relative energy levels of the d orbitals have been determined as d.T:, dy:Canadian Journal of Chemistry, 46, I444 (1968) In the last few years there has been considerable interest in the electronic structures of square planar metal complexes. Much of this interest has been due to the fact that the relative energies of the d orbitals in square planar complexes are not known with certainty, even in compounds of D,, symmetry. Information regarding the ordering of the energy levels of the d orbitals often may be obtained by examining the absorption spectra of the complexes. However, for many of the square planar complexes it has been difficult to observe the bands due to d-d transitions because of very strong overlapping with the charge transfer bands. This is particularly found to be the case when n-bonding ligands such as CN,-are present and as a consequence the d-d absorption bands usually occur only as shoulders in the region of the low energy charge transfer band or are completely hidden.Gray and other workers (1-4) have studied various square planar complexes with cyanide ions and have attempted to determine energy levels from the observed transitions. However, in most cases the peaks due to the d-d transitions were well hidden. We wish to report a study of the [~i(cN),]'-ion which gives further insight into the relative ordering of the energy levels of the molecular orbitals in this type of compound.The study was suggested by a recent paper (5) in which circular dichroism (c.d.) was reported for the [PtC1,I2-ion in optically active 2,3-butanediol. In the region of one of the d-d transitions, a c.d. band was observed and this was attributed to the concentration of the dissymmetric influences of the solvent to the tetragonal (f z and -z) positions of the ion.We have examined the [Ni(CN),I2-complex in a similar optically active solvent (cl-1,2-propanediol) and have found evidence for two c.d. bands. The observed spectra are shown in Fig. I . The bands are quite reproducible for a given set of conditions and remain relatively unchanged over a period of 1 to 2 weeks. Due to very strong absorption by both the solvent and solute, the c.d. maximum for the high energy band could not be obtained. However, it is unquestionable that a second negative c.d. peak does occur and some rounding of the curve at approximately 272 mp is indicated.For [PtCl4I2-, the observed c.d. was attributed to the ' A , , -> 'A,, transition (5). This assignment would correspond to an arrangement of the d-orbitals which is different from that given by Gray and Ballhausen (1). Recently new molecular orbital calculations have been made (6) and the ordering of energy levels in [~t C l , ]~-is now given as d22 < dxz, dyz < dxy < dX2-y2.

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“…Our c.d. energy since it is stabilized by overlap with the results are consistent with his views and those of 4p, orbital (1).…”

supporting

confidence: 89%

mentioning

confidence: 94%

Circular dichroism of the tetracyanonickelate(II) ion

Haines¹,

Smith²

1968

Can. J. Chem.

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“…However, the relatively small splitting of the SO, stretching frequencies of -150cm-I, the occurrence of the highest frequency SO stretch at -1340cm-', the position of the bridging SO stretch at a relatively high 1000 to 1035 cm-I, and the low S F stretch at 800 cm-I , all are indicative of the retention of ionic character and weak covalent interaction with the metal in the Table 2 and compared to values for solid K, [PdCl,], discussed previously by Gray and Ballhausen (12). All three bands found are assignable to d-d transitions, and charge transfer bands found in solution spectra of [PdC1,I2-at 36000 and 44000cm-' were not observed for the fluorosulfates and are possibly outside the range of our instrument.…”

Section: Resultsmentioning

confidence: 52%

Fluorosulfates of palladium. Part 3. The tetrakis(fluorosulfato)palladate(II) ion

Lee¹,

Aubke²

1981

Can. J. Chem.

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The reduction of ternary fluorosulfato complexes of palladium(IV) like cesium hexakis(fluorosulfato)palladate(IV) by bromine in liquid sulfur dioxide at room temperature or at slightly elevated temperatures results in the formation of cesium tetrakis(fluorosulfato)palladate(II), according to:[Formula: see text]In contrast to all previously reported palladium(II) fluorosulfato derivatives, Pd2+ is found in a square planar environment resulting in diamagnetism.

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“…In all complexes charge transition spectra occurred at the 420 nm and to 428nm. The electronic spectra of these complexes indicate square planar geometry [15][16] for all complexes.…”

Section: Resultsmentioning

confidence: 99%