  We have imaged the kpc scale distribution of 12CO(J=1-0) emission in the ring
galaxy Arp 143 (NGC 2444/5) using the OVRO millimeter array. We find two giant
molecular complexes in the ring component (NGC 2445) and a bright central
source. The ring complexes comprise 20-60% of the detected H_2 mass, depending
on the relative I(CO)-N(H_2) for the ring & nucleus. Their individual H_2
masses and surface densities (S(H_2)) exceed typical spiral GMAs regardless of
the conversion factor. Both are associated with a 6 kpc ridge of high S(HI) and
massive star formation (MSF) activity. H-alpha imaging shows a patchy ring of
HII regions situated along the HI ring's outer edge. The latter's kinematics
show clear signs of expansion. A simple rotating-expanding ring model (V_exp =
118+-30 km/s) fits the data well, implying a ring age of >~60+-15 Myr. NGC
2445's ring is able to promptly form very large molecular complexes in a metal
poor ISM and trigger MSF. Nearly 80% of the detected 12CO(1-0) flux originates
in a resolved central source that is slightly offset from NGC 2445's starburst
nucleus. We find an ordered velocity field in this component. Assuming an
inclined disk, we argue that it is dynamically stable. The central S(H_2)
significantly exceeds values typically found in normal spirals, but is much
smaller than S(H_2) derived in similar sized regions of IR luminous galaxies.
The nuclear H_2 may be the result of a previous encounter with NGC 2444.
12CO(1-0) emission in ring galaxies may be dominated by the nucleus, which
could bias the interpretation of single-dish measurements.
