Dppm bridged complexes

Addition of a catalytic amount of BPK to a 14/dppm/THF solution at 288 K affords a quantitative yield of 15, in which the dppm is monodentate, within 1 min (Scheme 6). The thermal reaction of 14 with dppm in hexane affords the dppm-bridged complex, 16. The substitution of equatorial carbonyls to form pt-r -dppm products has been confirmed in a number of cases by X-ray crystallography, for example, [Co2(/a-PhC2Ph) (ja-dppm)(CO)4j (Fig. 7).60 Solution dynamics studies of [Co2( t-aIkyne) (ju.-dppm)(CO)4] complexes show that an effective mirror plane that contains the cobalt-cobalt bond and the two phosphorus atoms is generated on the NMR time scale.61 This can be interpreted as a rocking motion of the alkyne about the cobalt-cobalt bond. Complex 16 is also produced... 

The reactivity of the bis-dppm-bridged complexes described above, although diverse, suggests a common mechanism of dihydrogen activation initiated by a single-metal addition. After this common activation step, the feasibility of subsequent reactions such as hydride migrations, further dihydrogen additions, or reductive eliminations is determined by the specific features of each compound, which also define the nature of the final reaction product. 

Several other peroxo bridged complexes have been lately synthesized simply by reacting appropriate precursors and dioxygen, as shown in equation 7 for di-Ir(II) complex 5, with bis(diphenylphosphinomethane) dppm, and in equation 8 for a dicopper(II)... 

Analogous cyano complexes can be prepared. Treating the bis chelate complex [Pt(dppm)2]2+ with 2 equivalents of NaCN leads to stabilization of the r 1-dppm complex (151) which can be used to prepare heterobimetallic bridging complexes with added M (M= Ag+/I, HgCl2, Rh2Cl2(CO)4) (equation 433).1461 Similar complexes can be formed with dialkyl and diaryl substituents on platinum in place of cyanide.1462... 

Pyridyldiphenylphosphine forms a number of homo-and heteronuclear palladium dinuclear clusters with short Pd-M bonds (about 260 pm). They are usually made by comproportionation of a Pd(II) complex and a second complex in a low oxidation state, for example, Pd(0), Rh(I), Ru(0). For these derivatives, head-to-head and head-to-tail isomers are possible, but the latter seems to be preferred (Figure 2). The metal-metal bonds in these derivatives are not as reactive as in the corresponding dppm complexes and insertion reactions do not occur. Some single-bridged complexes, such as [Cp(CNR)Rh(/u.-PPh2Py)Pd(CNR)Cl]+ (Pd-Rh distance 263.1 pm) are also known. 

The dppm-bridged trihydride A-frame complex [Pt2H2(,u-H)( -dppm)2], prepared by NaBH4 reduction of [PtCl2(dppm)], loses H2 on treatment with neutral ligands ... 

---