The Cdouble bond; length as m-dashO and Cdouble bond; length as m-dashS bond cleavage in carbon dioxide and tolyl isothiocyanate by reactions with the Mo(0) tetraphosphine complex [Mo{meso-o-C6H4(PPhCH2CH2PPh2)2}(Ph2PCH2CH2PPh2)]

A Mo(0) complex containing a new tetraphosphine ligand [Mo(P4)(dppe)] (1; P4 = meso-o-C6H4(PPhCH2CH2PPh2)2, dppe = Ph2PCH2CH2PPh2) reacted with CO2 (1 atm) at 60 °C in benzene to give a Mo(0) carbonyl complex fac-[Mo(CO)(η3-P4double bond; length as m-dashO)(dppe)] (2), where the O abstraction from CO2 by one terminal P atom in P4 takes place to give the dangling P(double bond; length as m-dashO)Ph2 moiety together with the coordinated CO. On the other hand, reaction of 1 with TolNCS (Tol = m-MeC6H4) in benzene at 60 °C resulted in the incorporation of three TolNCS molecules to the Mo center, forming a Mo(0) isocyanide–isothiocyanate complex trans,mer-[Mo(TolNC)2(η2-TolNCS)(η3-P4double bond; length as m-dashS)] (4), where the S abstraction occurs from two TolNCS molecules by P4 and dppe to give the η3-P4double bond; length as m-dashS ligand and free dppedouble bond; length as m-dashS, respectively, together with two coordinated TolNC molecules. The remaining site of the Mo center is occupied by the third TolNCS ligating at the Cdouble bond; length as m-dashS bond in an η2-manner. The X-ray analysis has been undertaken to determine the detailed structures for 2 and 4.