The reaction with nickel tetracarbonyl, for example, proceeds through an unstable acyl nickel carbonyl complex which then undergoes electrophilic substitution to give the desired aldehyde (using H+ as the electrophile) or ketone (using an alkyl halide) product.
ðə ɹɪˈækʃən wɪð nˈɪkəl tˈɛtɹɐkˌɑːɹbənˌaɪl, fɔːɹ ɛɡzˈæmpəl, pɹˈoʊsiːdz θɹuː ɐn ʌnstˈeɪbəl ɐkˈɪl nˈɪkəl kˈɑːɹbənˌaɪl kˈɑːmplɛks wˌɪtʃ ðˈɛn ˌʌndɚɡˈoʊz ɪlˌɛktɹoʊfˈɪlɪk sˌʌbstɪtˈuːʃən tə ɡˈɪv ðə dɪzˈaɪɚd ˈældɪhˌaɪd jˈuːzɪŋ ˈeɪtʃ plˈʌs æz ðɪ ɪlˌɛktɹoʊfˈaɪl ɔːɹ kˈɛtoʊn jˈuːzɪŋ ɐn ˈælkaɪl hˈælaɪd pɹˈɑːdʌkt.