Syntheses, Structures, and Reactivity of Dinuclear Molybdenum−Platinum and Tungsten−Platinum Complexes with Bridging Carbonyl, Sulfur Dioxide, Isonitrile, and Aminocarbyne Ligands and a dppa Backbone (dppa = Ph<INF>2</INF>PNHPPh<INF>2</INF>)

The heterodinuclear μ-carbonyl complexes [(OC)<INF>4</INF>M(μ-CO)(μ-dppa)Pt(PPh<INF>3</INF>)] (<BO>3a</BO>, M = Mo; <BO>3b</BO>, M = W) are formed upon the reaction of [(OC)<INF>5</INF>M(η¹-dppa)] (<BO>1a</BO>, M = Mo; <BO>1b</BO>, M = W) with [Pt(C<INF>2</INF>H<INF>4</INF>)(PPh<INF>3</INF>)<INF>2</INF>]. After addition of p-tosylmethyl isonitrile to <BO>3</BO>, the CO bridge is replaced by a bridging isonitrile ligand to afford [(OC)<INF>4</INF>W(μ-C&dbd;NCH<INF>2</INF>SO<INF>2</INF>p-tolyl)(μ-dppa)Pt(PPh<INF>3</INF>)] (<BO>4a</BO>, M = Mo; <BO>4b</BO>, M = W). If stronger electron-donating isonitriles such as benzyl or 2,6-xylyl isonitrile are added to <BO>3</BO>, fragmentation into mononuclear complexes occurs. Protonation of <BO>4</BO> leads to the μ-aminocarbyne complexes [(OC)<INF>4</INF>M{μ-CN(H)CH<INF>2</INF>SO<INF>2</INF>p-tolyl}(μ-dppa)Pt(PPh<INF>3</INF>)][BF<INF>4</INF>] (<BO>5a</BO>, M = Mo; <BO>5b</BO>, M = W), which react further with isonitriles to yield the μ-aminocarbyne complexes [(OC)<INF>3</INF>(RNC)W{μ-CN(H)CH<INF>2</INF>SO<INF>2</INF>p-tolyl}(μ-dppa)Pt(PPh<INF>3</INF>)][BF<INF>4</INF>] <BO>6</BO>, (R = 2,6-xylyl, benzyl). Purging a solution of <BO>4a</BO> with SO<INF>2</INF> yields the complex [(OC)<INF>4</INF>Mo(μ-SO<INF>2</INF>)(μ-dppa)Pt(PPh<INF>3</INF>)], <BO>7a</BO>, in which a triphenylphosphine oxide ligand is bound via a hydrogen bridge to the N−H group of the dppa backbone. X-ray diffraction studies performed on <BO>4b</BO> and <BO>7a</BO> reveal that the μ-CNR and the μ-SO<INF>2</INF> ligands bridge the metal centers in an asymmetric manner, the Pt−μ-C or Pt−μ-S distances being significantly shorter than the corresponding W−μ-C or Mo−μ-S distances, respectively.