Manganese and iron PCP pincer complexes - the influence of sterics on structure and reactivity

The syntheses of various manganese and iron PCP pincer complexes via a solvothermal oxidative addition methodology is described. Upon reacting [Mn-2(CO)(10)] with the ligands (P(C-Br)P-CH2-iPr) (1a) and (P(C-Br)P-O-iPr) (1b), Mn(i) PCP pincer complexes [Mn(PCPCH2-iPr)(CO)(3)] (2a) and [Mn(-PCPO-iPr)(CO)(3)] (2b) were obtained. Protonation of 2a with HBF4 center dot Et2O led to the formation of [Mn(kappa P-3,CH,P-P(CH)P-CH2-iPr)(CO)(3)]BF4 (3) featuring an eta(2)-C-aryl-H agostic bond. The solvothermal reaction of 1a with [Fe-2(CO)(9)] afforded the Fe(ii) PCP pincer complex [Fe(PCPCH2-iPr)(CO)(2)Br] (4). Treatment of 4 with Li[HBEt3] afforded the Fe(i) complex [Fe(PCPCH2-iPr)(CO)(2)] (5a). When using the sterically more demanding ligands (P(C-Br)P-CH2-tBu) (1c) and (P(C-Br)P-O-tBu)(1d) striking differences in reactivity were observed. While neither 1c nor 1d showed any reactivity towards [Mn-2(CO)(10)], the reaction with [Fe-2(CO)(9)] and [Fe(CO)(5)] led to the formation of the Fe(i) complexes [Fe(PCPCH2-tBu)(CO)(2)] (5b) and [Fe(PCPO-tBu)(CO)(2)] (5c). X-ray structures of representative complexes are provided.

Automated summary

The synthesis of various manganese and iron PCP pincer complexes via solvothermal oxidative addition was described. The reaction with sterically demanding ligands exhibited significant differences in reactivity, leading to the formation of Fe(i) complexes. X-ray structures of representative complexes were provided for analysis.