Anionic d 8 Alkyl Hydrides – Selective Formation and Reactivity of Anionic cis ‐Pt II Methyl Hydride

The pincer‐type complexes [(PCN)PtR] {R = H, 2 ; Me, 4 ; PCN = C 6 H 4 [CH 2 P( t Bu) 2 ](CH 2 ) 2 N(CH 3 ) 2 } react with MeLi or Et 3 BHNa, to give anionic cis ‐Pt(Me)H complexes [(PCN*)Pt(H)(Me)] – Li + (Me trans to P; PCN* denotes the PCN ligand in which the amine arm is not coordinated) and [(PCN*)Pt(Me)(H)] – Na + (H trans to P). Only the isomer in which the incoming nucleophile is situated trans to the phosphane ligand is formed. These first d 8 anionic alkyl hydride complexes were fully characterized spectroscopically. The hemilabile PCN ligand allows for reversible de‐coordination of the amine arm, thereby providing a desirable balance of stability vs. reactivity. Theoretical calculations on model systems indicate a concerted mechanism in which the nucleophilic attack and the amine dissociation occur concurrently. The (unobserved) methane reductive elimination from the stable anionic methyl hydride complex [(PCN*)Pt(Me)(H)] – Li + ( 3 ) is thermodynamically and kinetically unfavorable, as indicated by DFT. This complex reacts with electrophiles, such as water and methyl iodide, to yield exclusively methane and the corresponding organometallic product (either 2 or 4 ). This reactivity was also further examined by DFT.