Construction of an iminoketenylidene

Abstract

The new isonitrile-μ-carbido complexes [WPt(μ-C)Br(CNR)(PPh3)(CO)2(Tp*)] (R = C6H2Me3-2,4,6, C6H3Me2-2,6; Tp* = hydrotris(dimethylpyrazolyl)borate) rearrange irreversibly in polar solvents to provide the first examples of iminoketenylidene (CCNR) complexes.

Transition Metal Carbide Complexes

“…Na­(PF 6 ) or Na­(BPh 4 ), does not preserve the bridging carbide ligands (Figure ). Instead, carbide-isocyanide coupling leads to iminoketenylidene complexes: [(Tp′)­(OC) 2 W­{μ-CCNAr}­Pt­(PPh 3 ) 2 ]­(PF 6 ) (Ar = 2,6-Me 2 -C 6 H 3 ) and [(Tp′)­(OC) 2 W­{μ-CCNAr}­Pt­(PPh 3 )­(CNAr)]­(PF 6 ) (Ar = 2,4,6-Me 3 -C 6 H 2 ) . Phosphine ligands coordinated to {WC–Ni} and {WC–Pd} complexes display similar coupling reactivity (see below, Figure ).…”

“…Instead, carbide-isocyanide coupling leads to iminoketenylidene complexes: [(Tp′)(OC) 2 W{μ-CCNAr}Pt(PPh 3 ) 2 ](PF 6 ) (Ar = 2,6-Me 2 -C 6 H 3 ) and [(Tp′)(OC) 2 W{μ-CCNAr}Pt(PPh 3 )(C NAr)](PF 6 ) (Ar = 2,4,6-Me 3 -C 6 H 2 ). 252 Phosphine ligands coordinated to {WC−Ni} and {WC−Pd} complexes display similar coupling reactivity (see below, Figure 97). Amusingly, this carbide-based coupling represents the only entry to iminoketenylidenes, highlighting the utility of carbide ligands as C 1 reagents.…”

“…Subsequently, the Pt 0 center inserts into the C–Br bond, forming [(Tp′)­(OC) 2 MoC–PtBr­(PPh 3 ) 2 ] (Figure and Figure ). Detailed studies by Hill have shown how the C–Br bonds of [(Tp′)­(OC) 2 MC–Br] complexes oxidatively add to the two-electron reductants, [Pd­(PPh 3 ) 4 ] and [Pt­(PPh 3 ) 4 ], to afford Pd II and Pt II derivatives: [(Tp′)­(OC) 2 MC–M′Br­(PPh 3 ) 2 ] (M = Mo, W; M′ = Pd, Pt). − These complexes engage in a wealth of ligand substitution reactions; for instance, this installs acetonitrile, isocyanide, diethyldithiocarbamate, diphosphine (dppe), as well as bis- and tris­(pyrazolyl)­borate (Bm – , Bp′ – , Tp′ – ) ligands on the Pd II and Pt II centers. In terms of reactivity, it is notable that ligand substitution reactions employing terpyridine, (substituted) bipyridines, and phenanthroline furnish stable cationic [(Tp′)­(OC) 2 WC–Pt­(terpy)]­PF 6 and [(Tp′)­(OC) 2 WC–Pt­(PPh 3 )­(L)]­PF 6 complexes (L = phen, R 2 bipy; R = H, t Bu) .…”

“…[(Tp′)(OC) 2 WC−Br] reacts with [Pt(PPh 3 ) 4 ] to generate a carbide-bridged complex, [(Tp′)(OC) 2 WC−PtBr(PPh 3 ) 2 ] (Figure 57), which sequentially exchanges its phosphine ligands with isocyanides to yield [(Tp′)(OC) 2 WC−PtBr(PPh 3 )-(CNAr)] and [(Tp′)(OC) 2 WC−PtBr(CNAr) 2 ] (Ar = 2,6-Me 2 -C 6 H 3 , 2,4,6-Me 3 -C 6 H 2 ). 252 The bis(isocyanide) complex is also accessible from [(Tp′)(OC) 2 WC−Br] and [Pt 3 (CNAr) 6 ]. Hill reported that the carbide-isocyanide complexes have labile bromide ligands.…”

Heterobimetallic μ2-halocarbyne complexes

“…Isonitriles are insufficiently electron withdrawing to serve this purpose, as demonstrated by the reaction of 1d with [Pt 3 (CNC 6 H 2 Me 3 -2,4,6) 6 ] (synthetically equivalent to 'Pt (CNC 6 H 2 Me 3 ) 2 ') to afford the μ 2 -carbido complex [WPt(μ 2 -C)Br (CNC 6 H 2 Me 3 ) 2 (CO) 2 (Tp*)]. 65 Nevertheless, if a freshly prepared solution of 3b is subjected to one atmosphere of CO, a clean reaction ensues to afford the monophosphine complex [WPt (μ 2 -CCl)(CO) 3 (PPh 3 )(Tp*)] (7, Fig. 15, Scheme 2) in which the chlorocarbyne remains intact and appears indefinitely stable and not prone to oxidative addition.…”