The GATE Grind

GATE 2023 CY – Question 40

Inorganic Chemistry · Instrumental Methods of Analysis: UV-visible, fluorescence and FT-IR spectrophotometry, NMR and ESR spectroscopy, mass spectrometry, atomic absorption spectroscopy, Mössbauer spectroscopy (Fe and Sn) and X- ray crystallography. Electroanalytical methods – cyclic voltammetry, ion-selective electrodes. Thermo-analytical methods: TGA, DTA and DSC. · 2 marks · Multiple choice

For the indicated hydrogen nuclei, the $^1H$ NMR multiplicities in I–IV, respectively, are ______.

I. Hydride H in $[HNi(OPEt_3)_4]^+$

II. Si–H in $Ph_2Si(Me)H$

III. H in $PH_3$

IV. Hydride H in $(Cp^*)_2ZrH_2$, where $Cp^*$ is pentamethylcyclopentadienyl.

  1. I- pentet, II- quartet, III- doublet and IV- singlet
  2. I- pentet, II- singlet, III- singlet and IV- doublet
  3. I- triplet, II- triplet, III- doublet and IV- doublet
  4. I- singlet, II- quartet, III- singlet and IV- singlet

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Show answer and explanation

Correct answer: (A) I- pentet, II- quartet, III- doublet and IV- singlet

Explanation

In I, coupling to four equivalent 31P nuclei(I=1/2) gives a pentet. In II, the Si–H signal couples to the three equivalent methyl protons, giving a quartet; minor isotope satellites are ignored. PH3 protons split by 31P into a doublet, and the two equivalent zirconium hydrides do not split each other, giving a singlet.

Thus **A**.