Chelate ring-opening of rhenium–diphosphine complexes by diazonium salts

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Abstract
Treatment of [ReCl(CO)5] with Ph2PC(CH2)PPh2(vdpp) gave trans-[ReCl(CO)(vdpp-PP′)2](1a); similar treatment with Ph2PCH2CH2PPh2(dppe) gave trans-[ReCl(CO)(dppe-pp′)2](1b) but Ph2PCH2PPh2(dppm) gave trans-[ReCl(CO)(dppm-pp′)2](1c) as a minor product, the main product being mer, cis-[ReCl(CO)2(dppm-PP′)(dppm-P)]. Treatment of [ReCl(CO)5] with Ph2PCHMePPh2(mdppm) gave trans-[ReCl(CO)(mdppm-PP′)2] as a mixture of two geometrical isomers; reduction of (1a) with sodium tetrahydroborate gave these same isomers but in different proportions. Treatment of (1a) with a solution of [4-FC6H4N2][PF6], even at –70 °C, caused immediate chelate ring-opening to give mer-[ReCl(CO)(N2C6H4F-4)(vdpp-PP′)(vdpp-P)][PF6], (5a), which was isolated in 90% yield; other diazonium salts, [4-MeC6H4N2][BF4], [4-MeOC6H4N2][PF6], or [2,6-Me2-C6H3N2][BF4], similarly effected chelate ring-opening to give analogous complexes. In the case of mer-[ReCl(CO)(N2C6H3Me2-2,6)(vdpp-PP′)(vdpp-P)][BF4] a mixture of two isomers was obtained; these were possibly due to restricted rotation around the Re–N2 bond caused by the bulky aryl group. Treatment of trans-[ReCl(CO)(mdppm-PP′)2](mixture of isomers) with [4-FC6H4N2][PF6] caused chelate ring-opening to give [ReCl(CO)(N2C6H4F-4)(mdppm-PP′)(mdppm-P)][PF6] as a mixture of two isomers The uncomplexed phosphorus of (5a) was methylated, on treatment with Me3O·BF4, to give [ReCl(CO)(N2C6H4F-4)(vdpp-PP′){Ph2PC(CH2)PMePh2}][BF4][PF6]. Treatment of (1b) with [4-FC6H4N2][PF6] caused oxidation to the ReII complex trans-[ReCl(CO)(dppe-PP′)2][PF6] and no ring-opening; treatment of the dinitrogen complex trans-[ReCl(N2)(dppm-PP′)2] with [4- FC6H4N2][PF6] gave trans-[ReCl(N2H6-4)(dppm-PP′)2][PF6], also with no ring-opening. Phosphorus-31 and 1H n.m.r. and i.r. data are given.

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