Novel double substrate insertion versus isocyanate extrusion in reactions of imidotitanium complexes with CO2: critical dependence on imido N-substituents

Reaction of the cyclopentadienyl-amidinate supported imidotitanium complexe s [Ti(eta -C5Me5){MeC((NPr)-Pr-i)(2)}(NR)] (R=Bu-t 1a or Ar 1b where Ar=2,6 -C6H3Me2) with CO2 proceed via initial cycloaddition reactions, but dependi ng on the imido N-substituent go on to yield products of either isocyanate extrusion or double CO2 insertion, the latter forming [Ti(eta -C5Me5){MeC(( NPr)-Pr-i)(2)}{O(CO)N(Ar)(CO)O}] 4; the double CO2 insertion reaction leadi ng to 4 is the first example for any transition metal imide.