  We show that repulsive local Coulomb interaction alone can drive
valence-skipping charge disproportionation in the degenerate d-band, resulting
in effective negative-U. This effect is shown to originate from anisotropic
orbital-multipole scattering, and occurs only for $d^1$, $d^4$, $d^6$ and $d^9$
fillings (and their immediate surroundings). Explicit boundaries for
valence-skipping are derived and the paramagnetic phase diagram for $d^4$ and
$d^6$ is calculated. We also establish that the valence-skipping metal is very
different, in terms of its local valence distribution, compared to the
atomic-like Hund's metal. These findings explains why transition metal
compounds with the aforementioned d-band fillings are more prone to
valence-skipping charge order and anomalous superconductivity.

Strongly Correlated Electrons