  Single-dish sub-millimeter observations have recently revealed the existence
of a substantial, chemically peculiar, molecular gas component located in the
innermost circumstellar environment of the very massive luminous blue variable
star $\eta$ Carinae. Here, we present 5$"$-resolution interferometric
observations of the 1$\rightarrow$0 rotational transition of hydrogen cyanide
(HCN) obtained with the Australia Telescope Compact Array (ATCA) toward this
star. The emission is concentrated in the central few arcseconds around $\eta$
Carinae and shows a clear 150 km s$^{-1}$ velocity gradient running from
west-north-west (blue) to east-south-east (red). Given the extent, location,
and kinematics of this molecular material, we associate it with the complex of
dusty arcs and knots seen in mid-infrared emission near the center of the
Homunculus nebula. Indeed, the shielding provided by this dust could help
explain how molecules survive in the presence of the intense UV radiation field
produced by $\eta$ Carinae. The dust located in the central few arcseconds
around $\eta$ Carinae and the molecular component described here have most
likely formed in situ, out of material expelled by the massive interacting
binary system. Thus, $\eta$ Carinae offers us a rare glimpse on the processes
leading to the formation of dust and molecules around massive stars that are so
relevant to the interpretation of dust and molecule detections at high
redshifts.
