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Chemical reduction of [Mo 2 Cp 2 (µ-Cl)(µ-PA 2 )-(CO) 2 ] (A ) Cy, Ph, OEt) gives the corresponding alkaline metal salts of the triply bonded anions [Mo 2 -Cp 2 (µ-PA 2 )(µ-CO) 2 ] -, which exhibit both molybdenum and oxygen nucleophilic sites. The PCy 2 anion reacts easily with NH 4 + , [AuCl(PR 3 )], or MeI to give unsaturated dicarbonyls [Mo 2 Cp 2 (µ-X)(µ-PA 2 )(CO) 2 ] (X ) H, AuPR 3 , Me), while [Me 3 O]BF 4 gives the methoxycarbyne [Mo 2 Cp 2 (µ-COMe)(µ-PCy 2 )(µ-CO)] and allyl chloride rearranges to give the unsaturated alkenyl complex [Mo 2 -Cp 2 (µ-PCy 2 )(µ-CMeCH 2 )(CO) 2 ].

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The triply bonded complex [Mo2Cp2(μ-H)-(μ-PCy2)(CO)2] (Cp = η5-C5H5) reacts readily at room temperature with a great variety of simple molecules, resulting in diverse processes, as illustrated by its reactions with CO (addition), CNtBu (insertion), and HSnPh3 (H2 elimination). This unsaturated hydride also easily incorporates 17e [MoCp(CO)3] or 16e [MnCp‘(CO)2] metal fragments to give 46e heterometallic clus-ters (Cp‘ = η5-C5H4Me).

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The effect of the phenanthroline substituents on the structure and reactivity of platinum(II) and platinum(IV) complexes has been investigated. The X-ray crystal structures of the compounds [PtI(2)(4,7-Ph(2)phen)].CHCl(3) (1dz.CHCl(3)), [PtI(4)(4,7-Ph(2)phen)].CHCl(3) (2dz.CHCl(3)), [PtI(2)(2,9-Me(2)-4,7-Ph(2)phen)] (1fz), and [PtI(4)(2,9-Me(2)-4,7-Ph(2)phen)].I(2) (2fz.I(2)) have shown that complexes 1fz and 2fz, containing ortho-substituted phenanthrolines, exhibit a remarkable displacement of the equatorial iodine atoms from the N-Pt-N' plane (average 0.477(2) and 0.199(2) Å, respectively), a bending of the phenanthroline [angle between outer rings of 19.9(7) and 14.2(7) degrees, respectively] and a rotation of the N-C-C'-N' plane with respect to the N-Pt-N' plane [32.3(10) and 26.5(9) degrees, respectively]. Comparison between the structures of 1fz and 2fz, both having the phenanthroline with methyl substituents in the ortho position, indicates that, in the latter case, because of the presence of the two axial iodine ligands, the displacements of the ligands from the equatorial plane are smaller and find a compensation in a narrowing of the I(1)-Pt-I(1') angle (5 degrees ) and a lengthening of the Pt-N bonds (0.07 Å). The electrochemical behavior of the four-coordinate platinum(II) complexes shows that compounds possessing regular planar geometry have access to the one-electron reduced species, whereas those with distorted coordination geometry are irreversibly reduced by collapsing of the complex geometry. This is in sharp contrast with the behavior of related nickel complexes for which the pseudo-tetrahedral coordination imposed by bulky 2,9-substituents of phenanthroline stabilizes the nickel(I) species. Spectroscopic results allow us to assign a significant Pt(I) character to [1d](-) monoanions. The electrogenerated, plus one electron, complexes are not indefinitely stable and, because of conjugation with the phen ligand, progressively restore the Pt(II) oxidation state by transferring the electron to the peripheral organic ligand. The latter process can involve multiple electron additions in the macroelectrolysis time scale. The related platinum(IV) complexes [PtX(4)(L)] undergo irreversible two-electron reduction accompanied by fast release of the axial ligands and formation of the corresponding platinum(II) species.