NOVELTY - An organometallic compound (I) or (II), is new.    USE - New organometallic compound is used as catalyst for dehydrogenating oxygen-containing compound and manufacturing hydrogen for fuel cell, and carbonyl compound (all claimed). Uses include but are not limited to pharmaceutical, agrochemical, foodstuff and fragrance.    ADVANTAGE - The organometallic compound has high solubility with respect to organic solvent, catalyst efficiency and reaction yield, and improves yield of decomposition reaction of formic acid or formate and dehydrogenation reaction of alcohol without using co-oxidizing agent. The decomposition reaction of formic acid or formate is economically performed at reaction temperature of 100 degrees C or less, by safe process.    DETAILED DESCRIPTION - An organometallic compound of formula (I), is new.    Ar=phenyl or cyclopentadienyl (both optionally substituted);    M=ruthenium, rhodium or iridium;    R1-R6=1-10C alkyl, 3-15C cycloalkyl, 6-15C aryl, 1-10C heterocyclyl, 2-10C alkenyl, 2-10C alkynyl, 1-10C alkoxy, 1-10C ester, 1-10C fluoroalkyl, 1-10C acyl, 1-10C sulfonyl, 1-10C amino, 1-10C amido, 1-10C sulfenyl or 1-10C silyl, in which one or two or more H is optionally substituted by halo, nitro, cyano, hydroxy, sulfo, mercapto or carboxy;    R3+R4=-CH=CH-, in which H is optionally substituted by R1;    L=aquo ligand;and    Z=Na, Li, K or Cs.    INDEPENDENT CLAIMS are included for the following:    (1) catalyst, which contains organometallic compound (I) or (II);    (2) dehydrogenation of oxygen-containing compound, which involves using catalyst containing the organometallic compound (I) or (II);    (3) manufacture of carbonyl compound, which involves dehydrogenating alcohol using catalyst containing the organometallic compound (I) or (II);    (4) manufacture of hydrogen, which involves dehydrogenating mixture containing alcohol and water, alcohol, or formic acid or formate using catalyst containing the organometallic compound (I) or (II); and    (5) system for manufacturing hydrogen, which consists of a recovery portion which recovers reaction tank in which dehydrogenation is performed, and a supply portion which supplies mixture and alkali compound.