Metalation of Aryl‐bis(3‐alkyl‐5‐methylpyrazol‐1‐yl)‐ methane (Alkyl=Me, Ad; Aryl=Ph, C 6 H 4 ‐2−OH) with NaN(SiMe 3 ) 2 , KN(SiMe 3 ) 2 , and Ca{N(SiMe 3 ) 2 } 2

Deprotonation of phenyl‐bis(3,5‐dimethylpyrazolyl)methane (HC(Ph)(Pz Me2 ) 2 , 1   a ) with [(thf) 2 Ca{N(SiMe 3 ) 2 } 2 ] in THF at −40 °C yields heteroleptic [(thf) 2 Ca{N(SiMe 3 ) 2 }{C(Ph)(Pz Me2 ) 2 }] ( 2   a ) and finally homoleptic [(thf)Ca{C(Ph)(Pz Me2 ) 2 } 2 ] ( 2   b ). However, these complexes degrade at room temperature to calcium bis(pyrazolate) and 2‐phenyl‐4,6‐dimethylpyrimidine ( 3   a ). This degradation is accelerated when bulky phenyl‐bis(3‐adamantyl‐5‐methylpyrazolyl)methane (HC(Ph)(Pz Ad,Me ) 2 , 1   b ) is treated similarly and 2‐phenyl‐4‐adamantyl‐6‐methylpyrimidine ( 3   b ) forms quickly. Sodiation of 1   a and 1   b with NaN(SiMe 3 ) 2 yields [{HC(Ph)(Pz Me2 ) 2 }Na{C(Ph)(Pz Me2 ) 2 }] ( 4   a ) and [{HC(Ph)(Pz Ad,Me ) 2 }Na{C(Ph)(Pz Ad,Me ) 2 }] ( 4   b ). The stronger metalation reagent benzylpotassium is able to quantitatively deprotonate 1   b leading to dinuclear [K{C(Ph)(Pz Ad,Me ) 2 }] 2 ( 4   c ). The metathetical approach and the reaction of 4   c with metal(II) halides of Mg, Ca and Zn again leads to degradation and formation of pyrimidine 3   b . This decomposition of the ligand can be circumvented when the sidearm contains the anionic charge. Thus, 2‐hydroxyphenyl‐bis(3‐adamantyl‐5‐methylpyrazol‐1‐yl)methane ( 1   c ) reacts with [(thf) 2 Ca{N(SiMe 3 ) 2 } 2 ] in THF to the homoleptic complex [(thf) 4 Ca{O−C 6 H 4 −CH(Pz Ad,Me ) 2 }] ( 2   c ). In this complex, THF and pyrazolyl bases compete in the coordination sphere and preparation of a heteroleptic complex fails. To avoid the binding competition between THF and pyrazolyl bases and to stabilize heteroleptic calcium complexes, the reaction has been repeated in toluene yielding [Ca{N(SiMe 3 ) 2 }{O−C 6 H 4 −CH(Pz Ad,Me ) 2 }] 2 ( 2   d ).