Propellanes as Drop-In ROMP Initiators

Addition of 1.1.1-propellane (111P) to (Ph3P)(3)MCl2 (M = Ru, Os) afforded 3-exo-methylenecycloalkylidene complexes (Ph3P)(2)Cl2M=((C4H4)-C-c)=CH2 (M = Ru, 1-PPh3; M = Os, 4-PPh3) via electrophilic ring opening. When they were combined in situ or when they were isolated, both 1-PPh3 and 4-PPh3 were competent at the ROMP of norbornene. Phosphine substitution of 1-PPh3 with P(c)Hex(3) generated ((c)Hex(3)P)(2)Cl2Ru=((C4H4)-C-c)=CH2 (1-P(c)Hex(3)), which was competent at norbornene ROMP and ring-closing metathesis. Similar in situ addition of tetracyclo[3.3.1.1(3,7).0(1,3)]decane (i.e., 1,3-dehydroadamantane, AdP) to (Ph3P)(3)RuCl2 yielded (Ph3P)(2)Cl2Ru. C{C9H14) (3-PPh3), a cyclohexylidene derivative with related reactivity. Self-metathesis of 1-PPh3 produced (Ph3P)(2)Cl2Ru=((C4H4)-C-c)=RuCl2(PPh3) (2-PPh3), which was structurally characterized. The use of C-13-labeled 111P* enabled identification of several alkylidene resonances in C-13 NMR spectra.

Automated summary

The addition of 1.1.1-propellane (111P) to (Ph3P)(3)MCl2 (M = Ru, Os) yielded 3-exo-methylenecycloalkylidene complexes capable of ring opening metathesis polymerization (ROMP) of norbornene. Phosphine substitution and self-metathesis reactions further demonstrated the reactivity of these complexes towards norbornene. The use of C-13-labeled 111P* allowed for the identification of multiple alkylidene resonances in C-13 NMR spectra.