Phosphines dinuclear

Although simple reactions of Re3X9L3 species under mild conditions leave the Re3(/r,-X)3X6 core structure intact, under more forcing conditions much more complex reactions occur. Thus, for example, with phosphines, dinuclear species such as Re2Cl5(PR3)3 and Re2Cl4(PR3)4 arise, although these are more conveniently available from [Re2Cl8]2, as noted in Section 18-D-5. 

Dioxygen and its ions can bind in mononuclear and dinuclear structures in a number of ways,962 as illustrated in Scheme 1. The typical reaction of dioxygen with Co compounds involves a number of these binding forms, outlined in Scheme 2. Mononuclear Co111—peroxo complexes are relatively rare, but yellow trigonal bipyramidal complexes [Co(02)L2]+ (L = chelating phosphines dppe or dppp) have been characterized structurally where the 022 is bonded to the Co in the side-on r]2 form (Co—O 1.858(7) 1.881(4) A), with O—O stretching frequencies ( 870 cm-1) consistent with Coin-peroxo speciation.963... 

Examples are tending to be more sophisticated and complex in form. For example, a dinuclear complex featuring a bridging phosphinate and phenolate in addition to peroxide (221) has been reported,966 as a model for phosphodiester systems. Apart from dicobalt(III) systems, a mixed-valence CoII,ni di-/i-superoxo complex (222) has been prepared.967 Transition between the three redox states CoII,n, Co11,111, and Co111111 is electrochemically reversible. 

Various type (967) dinuclear complexes with phosphido bridges have been prepared, usually by reduction of [(R3P)2NiX2] with, for example, sodium.2372-237 The terminal phosphines can be exchanged by other phosphines or by CO, yielding (968) and (969) in the latter case.2373,2374 Diphenylphosphide Ni1 complexes have also been prepared electrochemically.2376... 

Pt(en)(N03)2] and [Pt(OTf)2L2] (L = mono- or 1/2 bidentate tertiary phosphine) or dinuclear complexes of the type [Pt2(OTf)2(/i-monodentate tertiary phosphine cr-aryl = 4, -biphenyl, / -terphenyL 4,4 -benzophenone, etc.) other structural motifs employing platinum(II) have also been reported.2 0 The addition of bridging, multidentate N-donor ligands of various shapes and sizes to the labile complexes in a suitable solvent system has afforded several classes of discrete, plat-inum(II)-containing polygons, polyhedra, and catenanes. 

---