CO-Induced Reductive Elimination of P(t-Bu)₂H from the Platinum(II) Dinuclear Derivative Pt₂[μ-P(t-Bu)₂]₂(H)₂[P(t-Bu)₂H]₂, Affording Mononuclear Platinum(0) or Triangulo Triplatinum(I,I,II) Derivatives

Carbon monoxide (1 atm) quantitatively converts the Pt(II) dinuclear derivative Pt 2 [μ-P( t -Bu) 2 ] 2 (H) 2 [P( t -Bu) 2 H] 2 ( 1 ) into the new Pt I 2 Pt II triangulo cluster Pt 3 [μ-P( t -Bu) 2 ] 3 (H)(CO) 2 ( 2 ). The 44e - species 2 was characterized by IR and multinuclear NMR spectroscopy and by a single-crystal X-ray diffraction study. Complex 2 is formed through the slow CO-induced reductive elimination of P( t -Bu) 2 H from 1, affording the intermediate mononuclear Pt(0) carbonyl derivative Pt[P( t -Bu) 2 H] 2 (CO) 2 ( 4 ), which equilibrates with the carbonyl-bridged triangulo derivative Pt 3 [P( t -Bu) 2 H] 3 (μ-CO) 3 ( 5 ); these are the main products under high pressures of CO. Two alternative mechanisms were examined for the subsequent formation of complex 2, the first being the rapid condensation of complex 4 with unreacted 1 while the second assumes 5 as the direct precursor of 2 . Although the first mechanism cannot be conclusively rejected, the second seems the most appropriate, since under high pressures of CO/H 2 complex 2 was shown to equilibrate with 5 . In the presence of an excess of other phosphines, the carbonylation of 1 yields quantitatively the mononuclear monocarbonyl derivatives Pt(PR 3 ) 3 (CO) (R 3 = Ph 3, Et 3, t -Bu 2 H).