Reactions of tetraphosphine complex [Mo{meso-o-C6H4(PPhCH2CH2PPh2)2}(Ph2PCH2CH2PPh2)] with nitrile, CO, and isocyanide

When treated with three equivalents of PhCN in benzene at room temperature, [Mo(η4-P4)(dppe)] (1) containing a linear tetraphosphine meso-o-C6H4(PPhCH2CH2PPh2)2 (P4) as well as a diphosphine Ph2PCH2CH2PPh2 (dppe) afforded a nitrile complex [Mo(PhCN)(fac-η3-P4)(dppe)] (2), whereas treatment of 1 with CO (1 atm) in benzene at room temperature resulted in the formation of a 1:1 mixture of the CO analogue of 2 [Mo(CO)(fac-η3-P4)(dppe)] and a bis(carbonyl) complex cis-[Mo(CO)2(η4-P4)]. In contrast, reactions of 1 with XyNC (Xy=2,6-Me2C6H3) gave more diversified products varying from mono(isocyanide) to tris(isocyanide) complexes. Thus, reaction of 1 with an equimolar amount of XyNC gave a mixture of two isomers of mono(isocyanide) complex [Mo(XyNC)(fac-η3-P4)(dppe)] (5 and 6) along with a bis(isocyanide) complex cis-[Mo(XyNC)2(η4-P4)] (7). It has also been found that mono(isocyanide) complexes 5 and 6 are treated further with one equivalent of XyNC at elevated temperatures to form the expected bis(isocyanide) complex 7 as well as the other bis(isocyanide) complex trans-[Mo(XyNC)2(η2-P4)(dppe)] (8). By heating in solution, the latter was converted into the former. From the reaction of 7 with excess XyNC, a tris(isocyanide) complex [Mo(XyNC)3(fac-η3-P4)] was obtained. The X-ray analyses have disclosed the detailed structures for 2, 5, 7, and 8.