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Electronic structure in five-coordinate complexes of nickel(II) with heavy-donor ligands

Citation

Preer, James Randolph (1970) Electronic structure in five-coordinate complexes of nickel(II) with heavy-donor ligands. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/xfdt-p976. https://resolver.caltech.edu/CaltechTHESIS:09082015-093220306

Abstract

I.

Various studies designed to elucidate the electronic structure of the arsenic donor ligand, o-phenylenebisdimethylarsine (diarsine), have been carried out. The electronic spectrum of diarsine has been measured at 300 and 77˚K. Electronic spectra of the molecular complexes of various substituted organoarsines and phosphines with tetracyanoethylene have been measured and used to estimate the relative ionization potentials of these molecules.

Uv photolysis of arsines in frozen solution (96˚K) has yielded thermally labile, paramagnetic products. These include the molecular cations of the photolyzed compounds. The species (diars)+ exhibits hyper-fine splitting due to two equivalent 75As(I=3/2) nuclei. Resonances due to secondary products are reported and assignments discussed.

Evidence is presented for the involvement of d-orbitals in the bonding of arsines. In (diars)+ there is mixing of arsenic “lone-pair” orbitals with benzene ring π-orbitals.

II.

Detailed electronic spectral measurements at 300 and 77˚K have been carried out on five-coordinate complexes of low-spin nickel(II), including complexes of both trigonal bipyramidal (TBP) and square pyramidal (SPY) geometry. TBP complexes are of the form NiLX+ (X=halide or cyanide,

L = Qƭ(CH2)3As(CH3)2]3 or

P [hexagon - Q'CH3] , Q = P, As,

Q’=S, Se).

The electronic spectra of these compounds exhibit a novel feature at low temperature. The first ligand field band, which is asymmetric in the room temperature solution spectrum, is considerably more symmetrical at 77˚K. This effect is interpreted in terms of changes in the structure of the complex.

The SPY complexes are of the form Ni(diars)2Xz (X=CL, Br, CNS, CN, thiourea, NO2, As). On the basis of the spectral results, the d-level ordering is concluded to be xy ˂ xz, yz ˂ z2 ˂˂ x2 - y2. Central to this interpretation is identification of the symmetry-allowed 1A11E (xz, yz → x2 - y2) transition. This assignment was facilitated by the low temperature measurements.

An assignment of the charge-transfer spectra of the five-coordinate complexes is reported, and electronic spectral criteria for distinguishing the two limiting geometries are discussed.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Chemistry
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Gray, Harry B.
Thesis Committee:
  • Unknown, Unknown
Defense Date:12 August 1969
Funders:
Funding AgencyGrant Number
NSFUNSPECIFIED
Woodrow Wilson FoundationUNSPECIFIED
CaltechUNSPECIFIED
Record Number:CaltechTHESIS:09082015-093220306
Persistent URL:https://resolver.caltech.edu/CaltechTHESIS:09082015-093220306
DOI:10.7907/xfdt-p976
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9143
Collection:CaltechTHESIS
Deposited By: Leslie Granillo
Deposited On:09 Sep 2015 15:22
Last Modified:16 Apr 2021 22:31

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