The first examples of isonitrile insertion into a phosphido bridge and thecrystal and molecular structures of [Pt-2(mu-PBu2t){mu,eta(2)-P(Bu-2(t))C(=NAr)}(CNAr)(2)] and [Pt{mu,eta(2)-P(Bu-2(t))C (NHAr)}(CNAr)](2)(CF3SO3)(2)(Ar = p-tolyl)

The platinum(I) dinuclear carbonyl [Pt-2(mu -PBu2t)(2)((PBu2H)-H-t)(CO)] (1 ) reacts with organic isonitriles RNC (R = p-tolyl, Bu-t, PhCH2), yielding the mono- and disubstituted derivatives [Pt-2(mu -PBu2t)(2)((PBu2H)-H-t)(CN R)] (2, R = p-tolyl; 3, R = Bu-t; 4, R = PhCH2) and [Pt(mu -PBu2t)(CNR)](2) (5, R = p-tolyl; 6, R = Bu-t; 7, R = PhCH2). Only with the aromatic isonit rile does the reaction proceed through two further well-separated steps, gi ving [Pt-2(mu -PBu2t){mu,eta (2)-P(Bu-2(t))C(=NAr)}(CNAr)(2)] (8) and [Pt{m u,eta (2)-P(Bu-2(t))C(=NAr)}(CNAr)](2) (9). These arise from the unpreceden ted reversible isonitrile insertion into the M-P bonds of the phosphido-bri dges. When 8 or 9 are reacted with CF3SO3H, the cyclic carbenes [Pt-2(mu -P Bu2t){mu,eta (2)-P(Bu-2(t))C(NHAr)}(CNAr)(2)]CF3SO3 (10) and [Pt{mu,eta (2) -P(Bu-2(t))C(NHAr)}(CNAr)](2) (CF3SO3)(2) (11) are respectively formed. The crystal and molecular structures of complexes 8 and 11 were solved by X-ra y diffraction.