Reductive carbonylation route to Co(0) and Co(I) carbonyl complexes containing bridging, chelating and cleaved diphosphazanes. Structures of [Co(CO){P(OR)2(NHMe)}2{P(O)(OR)2}{P(H)(OR′)2}] (R=CH2CF3, R′=CH2CH3), [Co2(CO)2{μ-MeN{P(OR)2}2}3] (R=CH2CF3), and [Co(CO){η2-MeN{P(OR)2}2}2][CoCl3(OC4H8)] (R=Ph)