SME
Inorganic Chemistry · Problem type
Hard, borderline or soft base
Use this for “Is PR₃ a hard or a soft base? Does it bind Pt²⁺ or Mg²⁺ more strongly?”
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Is the Lewis base hard, borderline or soft?
Tap a card, then tap its group.
Find the donor atom: small and highly electronegative (F, O) is hard; large and easily polarized (I, S, P, C) is soft.
Assumptions
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A Lewis base gives an electron pair; the donor atom is the one that bonds to the acid (C in CN⁻ and CO, P in PR₃).
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R stands for an alkyl or aryl group, as in R₂S (a thioether) and PR₃ (a phosphine).
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Hard bases bind hard acids best and soft bases soft acids.
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Absolute hardness and electronegativity
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Electronic spectra of complexes (Tanabe–Sugano)
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