The promotion of air oxidation and carbonyl substitution reactions of [(η5-C5H5)2Mo 2(CO)4(μ-RCCR′)] by trimethylamine N-oxide or nitrosonium tetrafluoroborate: the synthesis of [(η5-C5H5)2Mo 2(O)2(μ-O)(μ-RCCR′)] (R = R′ = CO2Me or Ph; R = H, R′ = Ph; or R = H, R′ = CO2Me) and [(η5-C5H5)2Mo 2(CO)3(NO)(μ-RCCR′)][BF4 ] (R = R′ = CO2 Me, Me or H; or R = H, R′ = CO2Me)