Synthesis of MCM-22 zeolite has been achieved without agitation. MCM-22 samples prepared with and without agitation were characterized by various physical methods. With all synthesis parameters except agitation during crystallization remaining the same, MCM-22 zeolite prepared without agitation contains a lower Si/Al ratio and larger crystallite size than MCM-22 obtained with agitation. After exchange by Ni(II), Ni(I) is stabilized in Na-MCM-22 zeolite by thermal and hydrogen reduction and characterized by electron spin resonance spectroscopy. NiNa-MCM-22 heated under vacuum at temperatures above 673 K for prolonged periods produces a weak isolated Ni(I) species with g(perpendicular to) 2.106. When dehydrated and oxidized NiNa-MCM-22 is reduced with hydrogen, two isolated Ni(I) species are observed, depending on the reduction temperature. The two Ni(I) species interconvert thermally. Adsorption of D2O on reduced NiNa-MCM-22 leads to the formation of a Ni(I)-(D2O), complex. Adsorption of ammonia on reduced NiNa-MCM-22 leads to a Ni(I)-(ND3)(n) complex with similar ESR characteristics. The similar ESR spectra suggest that both species are localized at the same site in the molecular sieve structure and have similar symmetry with two or three molecular ligands coordinated by the Ni(I) ion. Adsorption of ethylene on NiNa-MCM-22 produces two Ni(I)-(C2H4)(n) complexes located at different sites. Similarly, methanol adsorption on NiNa-MCM-22 leads to the formation of two Ni(I)-(CH3-OD)(n) complexes with axially symmetric g values. The behavior of Ni(I) in MCM-22 zeolite to form more than one complex with relatively large molecules such as methanol and ethylene can be explained on the basis of the two independent pore structures in MCM-22.