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.