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Reduction of neutral metal clusters (Co4(CO)12, Ru3(CO)12, Fe3(CO)12, Ir4(CO)12, Rh6(CO)16, {CpMo(CO)3}2, {Mn(CO)5}2) by decamethylchromocene (Cp*2Cr) or sodium fluorenone ketyl in the presence of cryptand[2.2.2] and DB‐18‐crown‐6 was studied. Nine new salts with paramagnetic Cp*2Cr+, cryptand[2.2.2](Na+), and DB‐18‐crown‐6(Na+) cations and [Co6(CO)15]2– (1, 2), [Ru6(CO)18]2– (3–4) dianions, [Rh11(CO)23]3– (6) trianions, and new [Ir8(CO)18]2– (5) dianions were obtained and structurally characterized. The increase of nuclearity of clusters under reduction was shown. Fe3(CO)12 preserves the Fe3 core under reduction forming the [Fe3(CO)11]2– dianions in 7. The [CpMo(CO)3]2 and [Mn(CO)5]2 dimers dissociate under reduction forming mononuclear [CpMo(CO)3]– (8) and [Mn(CO)5]– (9) anions. In all anions the increase of negative charge on metal atoms shifts the bands attributed to carbonyl C–O stretching vibrations to smaller wavenumbers in agreement with the elongation of the C–O bonds in 1–9. In contrast, the M–C(CO) bonds are noticeably shortened at the reduction. Magnetic susceptibility of the salts with Cp*2Cr+ is defined by high spin Cp*2Cr+ (S = 3/2) species, whereas all obtained anionic metal clusters and mononuclear anions are diamagnetic. Rather weak magnetic coupling between S = 3/2 spins is observed with Weiss temperature from –1 to –11 K. That is explained by rather long distances between Cp*2Cr+ and the absence of effective π–π interaction between them except compound 7 showing the largest Weiss temperature of –11 K. The {DB‐18‐crown‐6(Na+)}2[Co6(CO)15]2– units in 2 are organized in infinite 1D chains through the coordination of carbonyl groups of the Co6 clusters to the Na+ ions and π–π stacking between benzo groups of the DB‐18‐crown‐6(Na+) cations. [ABSTRACT FROM AUTHOR]