New crystal data of some solid transition‐metal complexes

X‐ray powder data have been recorded for the 32 complexes: Cu L 2 X 2 [ L = 2‐(2‐pyridyl)acetamide (aapH), N ‐(2‐pyridyl)benzamide (bapH), N,N ′‐diacetyl‐2,6‐diaminopyridine (daapH), N,N ′‐dibenzoyl‐2,6‐diaminopyridine (dbapH); X = Cl, Br]; ML 2 X 2 ( M = Ni, Co; L = aapH, bapH, daapH, dbapH; X = Cl, Br, I). These data indicate that, in all cases: ( a ) complexes ML 2 X 2 ( M = Ni, Co; X = Cl, Br, I) are isomorphous; ( b ) complexes Cu L 2 X 2 ( X = Cl, Br) are isomorphous; ( c ) the Cu complexes are not isomorphous with the Ni and Co analogues (a difference ascribed to the Jahn–Teller effect); and ( d ) the three points ( a )–( c ) above are consistent with the available spectral and magnetic data.